Chemical Reactions and Equations
Q.1. What is the general name of substances which are added to fat & oil containing
food to prevent rancidity. (1 Mark)
Ans. Antioxidants
Q.2. Write balanced chemical equation for the reaction of barium chloride with
Aluminium sulphate. (1 Mark)
Ans. 3 BaCl2 + Al2 (SO4)3 3 BaSO4 +2AlCl3.
Q.3. Identify the substance that is oxidised and the substance that is reduced in the
following reaction. 4 Na+O2 2 Na2O (1 Mark)
Ans. Substance Oxidised Na
Substance reduced O2
Q.4. Why does the colour of copper sulphate solution fade when iron nail is dipped in
it. (2 Mark)
Ans. The solution changes into iron sulphate Fe+CuSO4 FeSO4 + Cu
Q.5. What happens when quick lime is added to water? Write the chemical equation.
Which type of reaction is it endothermic or exothermic? (2 Mark)
Ans. Calcium oxide reacts vigorously with water to produce slaked lime (Calciumm hydroxide)
CaO+H2O Ca (OH)2 +Heat energy. It is an exothermic reaction.
Q.6. Silver chloride turns grey when kept in sunlight. Write chemical equation for it.
What type of reaction is it? (2 Mark)
Ans. 2 Ag Cl Sunlight 2 Ag (S) + Cl2 (g). It is a decomposition reaction
where light energy is absorbed. So it is an endothermic reaction.
Q.7. What happens when potassium iodide solution is added to lead nitrate solution? Give equation of the reaction involved. What type of reaction is represented by this example? (3marks)
Ans. When potassium iodide solution is added to lead nitrate solution, then a yellow
precipitate of lead iodide is formed alongwith potassium nitrate solution
Pb(NO3)2 (aq) + 2KI (aq) PbI2 (S) + 2 KNO3 (aq)
This is an example of a double displacement reaction. It is also a precipitation
Reaction.
Q.8. When a green iron salt is heated strongly, its colour finally changes to black and the odour of burning sulphur is given out.
a)Name the iron salt.
b)Name the type of reaction that take place during the heating of iron salt.
c)Write a chemical equation for the reaction involved. (3 Marks)
Ans:- a) Ferrous Sulphate
b) Thermal decomposition
c) 2 FeSO4 (S) Heat Fe2O3(s) + SO2 (g) + SO3 (g)
(Ferrous sulphate) (ferric oxide)
Green Colored Reddish brown.
Q. 9. Which type are the following reactions?
a) NH4Cl NH3 + HCl.
b) Fe + CuSO4 Fe SO4 + Cu
c) Ag NO3 + NaCl AgCl + NaNO3
d) PbO2 + SO2 PbSO4
e) CaCO3 CaO +CO2 (5 Marks)
Ans. a) Thermal decomposition reaction
b) Displacement reaction
c) Double displacement reaction
d) Combination reaction.
e) Thermal decomposition reaction
Q.10. Write balanced chemical equations for the following reactions:-
(5 Marks)
a) Dilute Sulphuric acid is poured on zinc granules
b) Iron reacts with steam
c) Carbon dixide reacts with water in the process of photosynthesis
d) Limestone is heated strongly.
e) Silver chloride is kept in sunlight in a china dish.
a) Zn + H2SO4 ZnSO4 + H2.
b) 3 Fe + 4H2O Fe3O4 + 4 H2
c) 6CO2 + 6H2O Sunlight C6H12O6 +6O2
d) CaCo3 Heat Chlorophyll CaO +Co2
e) 2 Ag Cl 2 Ag + Cl2
Chapter 2
Acids, Bases & Salts
1. How is the concentration of hydronium ion (H3O+) affected when a solution of an
acid is diluted? (1 Mark)
Ans. The concentration of hydronium ions, decreases when a solution of an acid is
Diluted.
2. Fresh milk has a PH of 6. How do you think the PH will change as it turns into curd? (1 Mark)
Ans. Its PH will decrease due to the production of lactic acid which is acidic in nature.
3. What is the PH of acid rains? ( 1 Mark )
Ans. Less than 5.6
4. Tooth enamel is one of the hardest substances in our body. How does it undergo
damage due to eating chocolates & sweets. What should we do to prevent it ?. ( 2 marks )
Ans. The bacteria present in mouth produce acids by the degradation of sugar & food
particles present in the mouth after eating. The acid so produced corrodes tooth
Enamel (Ca3(PO4)2). In order to prevent tooth decay we should clean the mouth
after eating food & we should use alkaline tooth paste.
5. Explain why for diluting an acid concentrated acid is added to water & not water to concentrated acid ?
Ans. This is because the process of dissolution of an acid in water is highly exothermic
process. For dilution the acid must be added slowly to water with constant stirring.
If water is added to acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may also break due to excessive local heating.
6. A house wife found that the cake prepared by her is hard and small in size. Which
ingredients has she forgotten to add that would have made the cake fluffy? Give
reason.
Ans. She has forgotten to add baking powder. When baking powder is added [Sodium bicarbonate and tartaric acid mixture] during the preparation of cake and heated then
sodium bicarbonate reacts with tartaric acid to form CO2 gas. This CO2 evolved
makes the cake to rise and become light and fluffy. Since the cake prepared by the
house wife is small and hard, it means that she had forgotten to add baking
powder.
Q.7. You have been provided with three test tubes. One of them contains distilled water
and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, have will you identify the contents of each test
tube?
Ans. Dip red litmus paper in solution repeatedly in each tube.
(a)The tube in which the red litmus paper turns purple contains distilled water.
(b)The tube in which red litmus paper turns blue contains basic solution.
(c)The tube in which red litmus paper remains red contains acidic solution.
Q.8. Do basic solutions also have H+ (aq) ions? If yes, then why are these basic? What is an alkali ? (3 Marks)
Ans: Basic solutions also contain H+ (aq) ions. But in basic solutions:
[H+] <> 10-7 M
Since (OH-aq) is more than [H+aq]hence these are basic solutions.
Bases that are soluble in water are called alkalis. For example NaOH, KOH, Ca(OH)2
Q. 9. What is neutralization reaction? Write 3 applications of neutralization reaction.
Ans. Neutralization it is an interaction of an acid with a base to form salt and water.
e.g. HCI + NaOH NaCl + H2 O
Acid Base Salt Water
Q. 10. Application :(i) Antacids neutralize the excess acids in our stomach and relieve us
from pain Ex-magnesium hydroxide (milk of magnesia).
(ii) If the pH of the sail is less than 7 i.e. it is acidic, the farmer will treat the soil
with quick time, slaked time, chalk etc to neutralize the acidity.
(iii) Bee sting contains methanoic acid which causes pain and irritation. Use of
mild base. Ex baking soda neutralizes it.
Q 10. a) How do metal carbonates and metal hydrogen carbonates react with acids?
Explain with the help of an activity.
(b) What happens when sulphuric acid in rain reacts with calcium carbonate in buildings
Made from limestone? (5marks)
Ans. (a) All metal carbonates and hydrogen carbonates react with acids to form a
corresponding salt, carbon dioxide & water.
Metal Carbonate + Acid -> Salt + Carbon dioxide + water
Metal hydrogencarbonate + Acid -> Salt + Carbon dioxide + Water.
For ex, Sodium carbonate reacts with dilute hydrochloric acid as follows:-
Na2CO3 (S) + 2 HCI (aq) -> 2 NaCI (aq + H20 (l) + CO2 (g)
Sodium hydrogen carbonate reacts with dilute hydrochloric acid as follows:-
NaHCO3 (S) + HCI (aq) -> NaCI (aq) + H2O(l) + C02 (g)
Activity :- Text book page number 20 Activity 2.5
Observation:- CO2 is produced with an effervescence. When this gas is allowed to
pass through lime water it becomes cloudy. It is a test for CO2.
b) When sulphuric acid in rain reacts with calcium carbonate in buildings made
from limestone calcium sulphate and Carbon dioxide is produced.
CaCO3 + H2SO4 -> CaSO4 + CO2 + H2O.
Chapter -3
Metals & Non-Metals
Q.1. What would happen to a copper vessel if it is left for a few days in humid
atmosphere without being cleaned ? (1)
Ans:- The surface will get corroded with the formation of a green layer of copper
carbonate.
Q.2. Why is ZnO Called an amphoteric oxide? Show with the help an equation.
Ans. ZnO is called an amphoteric oxide because it shows both acidic as well as basic
behaviour, i.e., it reacts with both acids (eg. HCl) as well as bases(Eg. NaOH) to form salt & water.
ZnO + 2HCl -> ZnCl2 + H2O
ZnO + 2 NaOH -> Na2 ZnO2 + H2O
Q.3. Write the chemical equation for the reaction of hot aluminium with steam.
Ans. 2 Al + 3 H2O -> Al2O3+ 3H2
Q4. An element reacts with oxygen to form an oxide which dissolves in dilute HCl. The
Oxide also turns a solution of red litmus blue. Is the element a metal or a non-metal?
Explain with help of a suitable example.
Ans. The element is a metal. Taking the example of Na Metal, its oxide will be Na2O . It
dissolves dilute HCI as follows:
Na2O + 2 HCI -> 2NaCl + H2O
Na2O as well as all other metal oxides are basic. For example, Na2O is basic as it dissolves in water to form NaOH which is a base. Basic oxides turn red litmus blue.
Q.5. Give reasons for the following:
(i) Carbon is not used for making aluminium from aluminium oxide.
(ii) Al easily combine with oxygen but still can be used for making kitchen utensils. (2)
Ans. (i) Carbon is not used for making aluminium from aluminium oxide because
aluminium has greater affinity to oxygen than for carbon. Hence carbon cannot
reduce aluminium oxide to aluminium.
(ii)Aluminium easily combines with 02 to form a layer of aluminium oxide. This layer, however, acts as a protective layer and doesn’t allow the metal underneath to react further.
Q.6. What is activity series of metals? Arrange Al, Zn, and Mg. in an increasing order of reactivity. (2)
Ans. The arrangement of metals in order of their decreasing reactivity with respect to other is called activity series of metals. The increasing order of the given metals is: Hg <> Zn SO4 + Cu
(iii) Reaction of metals with HNO3 doesn’t evolve H2 gas. It is because HNO3 is a strong oxidizing agent. It oxidizes H2 produced to water and is itself reduced to any of its oxides such as N20. NO. or NO2.
Q8. Write chemical equations for the reactions taking place when
i)Zinc carbonate is calcined
ii)Cinnabar (HgS) is heated in the air.
iii)Manganese dioxide is heated with aluminium powder. ( 3 )
Ans. i) Zn CO3 (S) Calcination ZnO (S) + CO2 (g)
ii) 2HgS (S) + 302 (g) Heat 2HgO (S) + 2SO2 (g)
2HgO-> 2Hg (l) + O2 (g)
iv)3MnO2 + 4 Al. Heat 2Al2O3 + 3 Mn.
Q. 9. a) What is ionic bond?
b) How ionic bond is formed?
c) Write the formation of magnesium chloride. (5)
Ans. (a) The Chemical bond found by the transfer of electrons from one atom to another
is known as an ionic bond.
(b)An ionic bond is formed when one of the atoms can donate electrons to achieve the inert gas electronic configuration and other atoms need electrons to achieve the inert gas electronic configuration. When a metal (Usually 1, 2 or 3 electrons in outermost shell) reacts with a non-metal (usually 5, 6 or 7 electron in outermost shell), transfer of electrons takes place from metal atoms to the non-metal atoms and an ionic bond is formed.
(c)Formation of magnesium chloride (MgCl2). The atomic number of magnesium is 12. it has two electrons in its valence shell as shown below:
12 Mg – 2, 8, 2
Magnesium, therefore, has a tendency to lose the 2 valence electrons and in the
process attains the electronic configuration of neon
Mg-> Mg 2+ + 2e-
2, 8, 2 2,8
Chlorine (atomic number 17 ) has 7 electrons in the valence shell. It has a tendency to gain one electron to complete its octet.
Cl + e- Cl-
2,8,7 2,8,8
Thus, when magnesium and chlorine are brought together, the magnesium atom transfers its two valence electrons to two chlorine atoms. In the process both the atoms acquire the stable electronic configuration of nearest inert gases. The positively charged magnesium ion Mg2+ and negatively charged Chloride ions (Cl-) are now held together by the electrostatic force of attraction.
‾
Mg2+ + 2 Cl- Mg2+ 2 Cl- or MgCl2
This process can also be shown as below
(Mg 2+) [ ] 2 Mg xx
Q. 10. What is the difference between alloy & amalgam? Write the composition of brass & bronze. Write 2 properties of alloy. (5)
Ans. (a) Alloy – It is a homogeneous mixture of 2 or more metals or a metal and a non-metal.
Amalgam – If in an alloy one of the metals is mercury, then the alloy is an amalgam.
(b) Brass – Alloy of Copper and Zinc.
Bronze – Alloy of Copper and tin.
(c) Properties of alloy – (i) The electrical conductivity and melting point of an alloy is
less than that of pure metal.
(ii) Alloy does not corrode easily.
CHAPTER-4
Carbon and its Compounds
Q1. What is denatured alcohol? (1)
Ans:- Ethane is made unfit for drinking by adding poisonous substances like methane to it. Dyes are also added to colour the alcohol blue so that it can be identified easily. This is called denatured alcohol.
Q2. Name the product other than water formed on burning of ethanol in air? (1)
Ans:- Carbon dioxide gas.
Q3. Give the names of the functional groups: (1)
a) CHO b) C
Ans:- a) Aldehyde b) Ketone.
Q4. Why carbon forms compounds by sharing of electrons and not by formation of ions? ( 2)
Ans:- Carbon is tetravalent in nature. If it gains 4 electrons to form C 4- ions, then it will be difficult for 6 protons to hold on to 10 electrons.
To lose 4 electrons forming C4 + ion, it would require a large amount of energy to remove 4 electrons. Hence it forms bond by sharing of electrons.
Q5.Allotropy is a property shown by which class of substances: elements, compounds or mixtures? Give one example of allotropy. ( 2)
Ans. Elements show allotropy. For example, graphite, diamond and fullerenes are allotropic forms of carbon.
Q6. Under what conditions can a saturated hydrocarbon produce a sooty flame? (2)
Ans. Saturated hydrocarbon produce sooty flame only when burnt in limited supply of oxygen.Due to limited supply of oxygen, the incomplete combustion of the hydrocarbon takes place resulting in unburnt carbon producing sooty flame.
Q7.a) Draw the structure for the following compounds: (3)
i)Propanoic acid.
ii)Butanal
b) Why is conversion of ethanol acid considered as oxidation reaction?
ANS. a) H H O
H C C C OH
H H
Propanoic acid
H H H H
H C C C C = 0
H H H
Butanal
b) Ethanol is oxidised with alkaline potassium permanganate to form ethanoic acid. As the addition of oxygen takes place,therefore it is called oxidation reaction.
Q8. What happens when an ester is heated with a base such as sodium hydroxide? Write equation of the reaction which takes place? What is the special name for this reaction and for what purpose it is used? (3)
Ans. When an ester is heated with sodium hydroxide solution then the ester gets hydrolysed to form the parent alcohol and sodium salt of the carboxylic acid .
Example---When ethyl ethanoate ester is boiled with sodium hydroxide solution, then sodium eyhanoate and ethanol are produced.
CH3COOC2H5 + NaOH ---------CH3COONa + C2H5OH
Sodium Ethanol
Ethanoate
The alkaline hydrolysis of esters is known as saponification (soap making).This is because of the fact that this reaction is used for the preparation of soaps. When the esters of higher fatty acids with glycerol (oils and fats) are hydrolysed with sodium hydroxide solution,we get sodium salt of higher fatty acids which are called soaps.
.
Q9 a)What is the difference between soap and detergent in chemical composition ?
b)Why detergent remains effective in hard water while soap not for cleaning?
c)Explain the mechanism of the cleaning action of soap. (5)
Answer:- a) Soap:- It is sodium or potassium salts of long chain carboxylic acid.
Detergent:- It is ammonium or sulphonate salts of long chain carboxylic acids.
b) Soap reacts with calcium and magnesium chloride or sulphate which causes hardness of water to form an insoluble substance (scum). The charged ends of detergents donot form insoluble precipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hardwater.
c) Most dirt is oily in nature. Oil does not dissolve in water. The molecule of soap has two ends with differing properties. The ionic-end of soap dissolves in water while the carbon chain dissolves in oil. The soap molecules, thus form structures called micelles where one end of the molecule is towards the oil droplet while the ionic end faces outside. This forms an emulsion in water. The soap micelles thus helps in dissolving the dirt in water and we can wash our clothes clean.
10) Write the chemical equation for the following reaction:
a) Ethanoic acid with Sodium Carbonate
b) Ethanoic acid with Sodium Bicarbonate
c)Burning of Ethanol
d)Ethanoic acid with Sodiun Hydroxide
e) Heating Ethanol at 443K with excess concentrated sulphuric acid (5)
Anwser:- a)2CH3COOH + Na2Co3 2CH3COONa + H2O + CO2
b) CH3COOH + NaHCO3 CH3COONa + H2O + CO2
c)CH3CH2OH + O2 CO2 + H2O + heat and light
d) NaOH + CH3COOH CH3 COONa + H2O
Hot conc.
e) CH3 CH2OH CH2 = CH2 + H2O
H2SO4
5. PERIODIC CLASSIFICATION OF ELEMENTS
Q.1.What were the criteria used by Mendeleyev in creating his periodic table?
Ans.In creating his periodic table, Mendeleev was guided by two factors:-
(a). Increasing atomic masses and;
(b) Grouping together of elements having similar properties.
Q.2.Besides Gallium, which other elements have since been discovered that fill the gaps left by Mendeleev in this periodic table?
Ans.Scandium and Germanium.
Q.3.Name two elements you would expect to show same kind of chemical reactivity as Magnesium. What is your best choice?
Ans.Beryllium, Calcium and Strontium will show same kind of chemical reactivity as Magnesium because they are placed in the same group. Elements placed in the same group have similar outer electronic configuration.
Q.4.Looking at the resemblance of Hydrogen to alkali metals and the Halogen family, to which group and period should Hydrogen be assigned in Mendeleev’s periodic table?
Ans.Since properties of Hydrogen resemble both alkali metals and Halogens, it can be placed either in group IA or group VII A. Since Hydrogen has the lowest atomic mass, it is placed in period I.
Q.5.An atom has electronic configuration 2, 8, 7.
(a) What is the atomic number of this element?
(b) To which of the following elements would it be chemically similar:-
(i) 7N
(ii) 9F
(iii)15P
(iv)18Ar
Ans. (a) The atomic number of the element is 2+ 8+7=17.
(b) Electronic configurations of the given elements are:-
(i)N-2,5.
(ii)F-2,7.
(iii)P-2,8,5.
(iv)Ar-2,8,8.
Thus F having similar electronic configuration with 7 valence electrons would be chemically similar to the given element.
Q.6.The positions of three elements A, B, C in the periodic table are show below:-
Group 16 Group 17
- -
- A
- -
B C
(a) State whether C is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller than B in size?
(c) Which type of ion (cation or anion) will be formed by element A?
Ans.(a) Elements of group 17 have 7 electrons in their respective valence shell and have a strong tendency to gain an electron to complete their octet. So, A is a non-metal.
(b) On moving down a group, the atomic size increases and thus the force of attraction of the nucleus for the incoming electrons decreases. Hence the reactivity decreases. Therefore C is less reactive than A.
(c) B and C belong to the same period. On going from left to right in a period the nuclear charge increases but the number of shells remain same. Therefore atomic size decreases from left to right. Thus C is smaller in size than B.
Q.7.Use Mendeleev’s periodic table to predict the formulae for the oxides of K, C, Al, Si and Ba.
Ans.K2O, CO2, Al2O3, SiO2, BaO.
Q.8.A metal M forms an oxide having the formula M2O3. It belongs to third period of the modern periodic table. Give its atomic number and valency.
Ans.Atomic number of the element is 2, 8, 3=13 and its valency is 3.
Q.9.What are the uses of Modern Periodic table?
Ans.In modern periodic table, the elements with similar properties are placed together in the same group. If we know the properties of one element of the group, the properties of other elements of the group can be predicted. Thus it makes the study of elements systematic.
Q.10.Why is long form periodic table regarded better than Mendeleev’s periodic table?
Ans.It is due to the following reasons:-
(a)It is based on atomic number.
(b)There is no confusion regarding the position of isotopes.
(c)All groups are independent and there are no sub-groups.
(d)It is more systematic.
Chapter 6
Life Processes
VSA Question carrying 1 marks each
Q1. What are the main two types of nutrition?
Ans. Autotrophic and Hetrotrophic nutrition.
Q2. what does the word ‘Sapro’ mean?
Ans. The word Sapro means rotten.
Q3. What is the process of obtaining food in Amoeba called?
Ans. The process of obtaining food in Amoeba is called Phagocytes.
Q4. name the cellular organelles where the folloing processes take place (i) Photo synthesis (ii) Cellular aerobic respiration?
Ans. (i) Chloroplast (ii) Mitochondria.
Q5. What is the function of bile?
Ans. Bile brings about the emulsification of fats.
Q6. Where are hormones synthesized in plants?
Ans. In planyts hormones are synthesized in the shoot and root tips.
Q7. Name the largest artery in our body?
Ans. Aorta
Q8. What is the liquid part of blood called?
Ans. Plasma.
SAQ carrying 2 marks each.
Q1. What is emulsification?
Ans. Breakdown of the large fat droplets into smaller ones.
Q2. Why are plants green?
Ans. Plants posses green chloplastic pigments called chlorophyll which absorb most of the blue and red regions of the incident light. They reflect green light so the plants look green in colours.
Q3. State the function of epiglottis?
Ans. Epiglottis is a leaf like cartilaginous flap present at the anterior end of glottis. It closes the glottis during swallowing to check the entry of food into glottis.
Q4. In which form is (i) Carbohydrates stored in plants (ii)Food stored in animals.
Ans. (i) Carbohydrates are stored in the form of starch in plants.
(ii) In animals food is stored in the form of glycogen.
Q5. What is breathing?
Ans. It is aphysical process of inhalation or bringing in fresh air for obtaining oxygen and exhalation or taking out of foul air for elimination of CO2.
SAQ carrying 3 marks each.
Q1. Why are white blood corpulses called “Soldiers” of the body?
Ans. White blood corpulses are called soldiers of the body because they protect the body from infections by destroying foreign matter. They also manufacture antibodies which are responsible for immunity.
Q2. What happens to glucose which enters nephron along with filtrate during excretion in human beings. State two vital functions of kidney.
Ans. Glucose is reabsorbed in tubule.
Vital functions of kidney (i) Excreation, separation of nitrogenous wastes for elimination.
(ii) Osmoregulation, maintainance of balance of water and salts in the body through elimination if extra and retention if deficient.
Q3. When is blood clotting useful?
Ans. Cloting of blood is useful phenomenon to stop flowing of blood (bleeding) during cuts and accidents and at the time of accidents.
Q4. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Ans. Mammals and birds are warm blooded animals. They continiously use energy to maintain treir body temperature. They have a higher energy need and require more oxygenated blood for their cells. It is important that their oxygenated blood doesnot mixup with deoxygenated blood.
Long Answer Question carrying 5 marks.
Q1. Name the blood vessel that brings deoxygenated blood to the human heart (b) Which chamber of human heart receives oxygenated blood (c) Explain how oxygenated blood from this chamber is sent to all parts of the body?
Ans. (a) Pulmonary vein.
(b) Left arterium.
(c) After receiving the deoxygenated blood, the atium contract during this countraction the deoxygenated blood of the right atium is poured into the right ventricle. Then the ventricle contract and the deoxygenated blood flows to the lungs through pulmonary artery.
CHAPTER 7
CONTROL AND COORDINATION
Q1 Which gland secretes the growth hormone? (1)
Ans Pituitary gland (anterior lobe of pituitary).
Q2 Name the part of the hindbrain which is responsible for maintaining the posture and balance of the body. (1)
Ans Cerebellum.
Q3 Which hormone is responsible for the development of moustache and beard
in man ?
Ans Testosterone
Q4 Why is the use of iodised salt advisable ? (2)
Ans Iodine is essential for the synthesis of thyroxin hormone in the thyroid gland.
Thyroxin regulates carbohydrates , protein and fat metabolism in the body so
. as to provide the best balance for growth .In case of deficiency of iodine in
our diet , there is a possibility that we might suffer from goitre . Thus , use
of iodised salt is advisable to prevent iodine deficiency in the body .
Q5 Why are diabetic patients advised to take less sugar in their diet by the
doctor ? (2)
Ans Insulin hormone is secreted by the pancreas which helps in regulating blood
sugar level in our body .It is not secreted in proper amount in the body of
the diabetic patient. If the sugar level in the blood rises , it causes many
harmful effects . So the diabetic patients are advised to take less sugar .
Q6. What happens at the synapse between two neurons ? (2)
Ans. The information acquired at the end of the dendrite tip of a nerve cell sets
of a chemical reaction that creates an electrical impulse This impulse travels from the dendrite to the cell body , and then along the axon to its end .At
the end of the axon , the electrical impulse sets off the release of some
chemicals . These chemicals cross the gap or synapse and start a similar
electrical impulse in a dendrite of the next neuron .
Q7. What is the difference between sensory and motor neurons? Which part of the brain
is responsible for auditory reception and sensation of smell? (3)
Ans. Sensory neurons-These are the neurons that transmit impulses towards the central
nervous system (brain and spinal chord) through their axons.
Motor neurons- These are the neurons that transmit impulses from central nervous
system towards effectors (muscles or glands).
Specific part of brain is responsible for auditory reception and smell.
Q8 Draw a human brain and label its different parts? (3)
Ans Text book page no.118 & fig.7.3.
Q9 What is a reflex action? Explain with help of an example. Draw a labeled diagram
to show the reflex action? (5)
Ans a) Reflex action is spontaneous & involuntary response of effectors (muscles &
glands) to stimulus. It is extremely quick action that does not involve any thinking
by the brain.
b) When our hand accidentally touches the hot object, heat is sensed by the thermo receptors present in the skin of hand. The receptor triggers nerve impulse in sensory neuron. It transmits message to spinal cord. In spinal cord impulse is passed on to the relay neuron which ,in turn passes it to the motor neuron. The motor neuron transmits the instruction to a muscle in our arm. The arm muscles contract and pulls our hand away from the hot object.
c) Text book page no.117 fig7.2
Q10. a)How is the movement of leaves of a sensitive plant different from the movement of the shoot towards light? 5)
b)Name one plant hormone that promotes growth in plant and one plant hormone that inhibits growth?
c)How does phototropism occur in stem?
Ans a) The movement of leaves of a sensitive plant is neither towards nor away from stimulus like touch. While movement of shoot is towards stimulus like light .The movement of leaves of a sensitive plant is not directional while the movement of shoot is directional.
b)Plant hormone that promotes growth in plants-Auxin
Plant hormone that inhibits growth-Abscisic acid.
c)The movement of a plant part in response to light is called phototropism.
The shoot responds by bending towards light while roots respond by bending away from the light. We know that the plant stem responds to light and bends towards it due the action of auxin hormone.This happens as follows:
i)When sunlight comes from above, then the auxin hormone present in the tip of the stem spreads uniformly down the stem .Due to the equal presence of auxin, both the sides of the stem grow straight and with some rapidity.
ii)When the light falls on the right side of the plant, then the auxin hormone collects in the left side of the stem, away from the light. This is because auxin hormone prefers to stay in shade.
Thus more auxin hormone is present in the left side of the stem as compared to the right. The left side of stem, hence grows faster than its right side and therefore, the stem bends towards the right side (direction of light).
8.
Q1 Name any two sexually transmitted diseases?
Ans: 1] Gonorrhoea 2] syphilis
Q2 Write full form of IUCD and AIDS?
Ans: IUCD-Intra Uterine Contraceptive Device.
AIDS-Acquired Immuno Deficiency syndrome.
Q3 Where does fertilization take place in human female?
Ans: Fertilization takes place inside the fallopian tubes.
Q4 If a women is using Copper-T, will it help her in protecting sexually transmitted diseases?
Ans: Copper-T prevents fertilization but the chances of infection persist. So, Copper-T will not help her in protection against sexually transmitted diseases.
Q5 What are the advantages of sexual reproduction over asexual reproduction?
Ans: Due to reshuffling of chromosomes and crossing over, sexual reproduction brings about variation in almost all characters so that no two individuals are similar. Genetic changes contribute to evolution of species to form better organisms. Asexual reproduction does not contribute to evolution of species as there is no variation.
Q6 Why is vegetative propagation practiced for growing some type of plants?
Ans: Vegetative propagation is practiced in some plants because-
1.It is the only method of reproduction in seedless plants.
2.A full matured plant is obtained in a very short time.
3.It helps to preserve the characters of the plant the breeder desires.
4.It is an easy and economical method for multiplication of ornamental plants.
Q7 How does reproduction helps in providing stability to population of species?
Ans: Reproduction helps in providing stability to population by-
1.Introducing variation in the population through genetic combination that helps the population to tide over adverse environmental conditions and adapt to changing environment.
2.Balancing birth and death rate.
Q8 What could be the reasons for adopting contraceptive methods?
Ans: Contraceptive methods are adopted for the following purposes-
1.To avoid frequent and unwanted pregnancies.
2.To maintain good reproduction health.
3.To obtain protection from sexually transmitted diseases.
4.To restrict the number of children.
Q9 Differentiate between menarche and menopause?
Ans- Commencement of menstruation at puberty in human female is termed menarche and its stoppage at the age of 50yrs is called menopause.
Q10 What is the importance of DNA copying in reproduction?
Ans-DNA copying is an important phenomenon of reproduction through which the organisms pass their features to their offsprings. It maintains the genetic pool and the body design features in different generation of the species. DNA copying also produces variations due to genetic linkage and crossing over of chromosomes. Such variations are useful for the survival of species.
9.
Q1:-Give examples of two variations found in humans.
Ans: - 1. Human height
2. Free earlobe and attached earlobe
Q2:- Write the names of the components of DNA?
Ans: - Components of DNA are nucleotides. Each nucleotide has further three components-
1.Deoxyribose sugar
2.A nitrogenous base
3.A phosphate group
Q3:-Give two examples where environmental factors govern sex-determination?
Ans: - a) In turtle, high incubation temperature results in the development of female progeny.
b) In lizard high incubation temperature results in male progeny.
Q4:- What is genetic engineering? Give the full form of GMO.
Ans: - It is the technique of altering the genetic make up of an organism by inserting gene (or segment of DNA) from other organism into its DNA.
The full form of GMO is GENETICALLY MODIFIED ORGANISM.
Q5:- How are the areas of study – evolution and classification interlinked?
Ans:-Classification of organisms is based on relative similarities and differences among organisms. Resemblances in organisms are because they have arisen from a common ancestor and differences are due to adaptations to different types of environment. As the organisms can be graded in order of increasing complexity, it indicates the concept evolution.
Q6:-Why are small numbers of surviving tigers a cause worry from the point of view from genetics?
Ans: - With decreasing number of tigers, their genetic pool is also vanishing which is essential to maintain the ecological and food chain balance.
Q7: - Will geological isolation be a major factor in the speciation of an organism that reproduces asexually? Why or Why not?
Ans: -During asexual reproduction organisms undergo a little variation over generations .The variation in the genetic pool are not enough to raise a new species .Thus, any change resulting from geographical isolation may not be passed to the next generation.
Q7: -A man with blood group ‘A’ marries a women blood group ‘O’ and their daughter has blood group ‘O’. Is this information enough to tell you which of the traits –blood group ‘A’ or ‘O’ is dominant? Why or Why not?
Ans: - Blood group ‘A’ is dominant while ‘O’ is recessive character. If a man with blood group ‘A’ marries a woman with blood group ‘O’ and their daughter has blood group ‘O’ , then the man has one copy of ‘A’ and one copy of ‘O’ blood group.
Q8: - Differentiate between autosomes and sex chromosomes.
Ans: - 1. The pair of chromosomes that are responsible for development of body characters are called autosomes .In human body, there 22 pairs of autosomes.
2.The pair of chromosomes which are responsible for determining the sex of the individual called sex chromosomes .
Q9: -Why Mendel selected garden pea plant for his experiment.
Ans: - Mendel selected garden pea plant for his experiment because-
1. Pure varieties of pea were available.
2. Pea plants showed a number of easily detectable contrasting characters.
3. The flower structure of pea is such that it allows controlled breeding.
4. Pea flower normally remains closed and undergoes self pollination.
Q10:-How is the equal genetic contribution of male and female parents ensured in the progeny?
Ans:-The gametes responsible for the formation of progeny develop by the process of meiosis. During meiosis only one set of chromosomes (50% of Gene) is transferred to the gamete. When male and female gametes fuse, one set of chromosome from each parent cell come together and complete the genetic pool.So, progeny receives 50% genetic contribution through each gamete(male and female).
10.LIGHT – REFLECTION AND REFRATION
Q1:- Define 1 dioptre of power of lens?
Ans: - One dioptre is the power of a lens of focal length one metre.
Q2:- Why do you prefer convex mirror as a rear-view mirror in vehicles?
Ans: - A convex mirror produces an erect and highly diminished image of the objects.Further, since it is curved outwards; it gives a wider field of view.
Q3:- The refractive index of diamond is 2.42.What is the meaning of the statement?
Ans: - It means that light travels 2.42 times faster in vacuum than in diamond.
Q4:- One half of a convex lens is covered with a black paper. Will this lens produce a complete image of that object? Verify your answer experimentally. Explain your observation.
Ans:- Yes ,it will produce a complete image of the object.
This can be verified experimentally by observing the image of the distant object like tree on a screen when lower half of the lens is covered with a black paper. However, the brightness of the image gets reduced.
Q5:- How can you distinguish between a convex mirror, a plane mirror and concave mirror?
Ans: - With the help of virtual image of three mirrors, we can distinguish between three mirrors-
a)Plane mirrors will produce virtual image of the same size.
b)Concave mirrors will produce magnified virtual image.
c)Convex mirror will produce a diminished virtual image.
Q6:- The magnification produced by a plane mirror is +1.What does this mean?
Ans:- m = h’/h=1
Therefore, h’ = h
i.e, the size of the image is equal to the size of the object. +ve sign of m indicates that the image is virtual.
Q7:- Calculate the distance at which an object should be place in front of a thin convex lens of focal length 10cm to obtain a virtual image of double its size?
Ans:- f = +10cm
m = +2 (as the image is virtual)
As, m = v/u = 2
Or, V = 2u
As, 1/v -1/u = 1/f
Or, 1/2u - 1/u = 1/10
Or, - 1/2u = 1/10
Therefore u = -5cm
The object should be place at a distance of -5cm from the lens.
Q8:- A concave mirror of focal length 20cm is to be used as a shaving mirror. Which of the following is the suitable object distance from the mirror? Justify your answer.
a)10cm
b)20cm
c)30cm
Ans:- For using concave mirror as shaving mirror, u
Ans:-
As, n = c/v
V = c/n
= 3 x (10)8/2.42
= 1.24 x 108 m/s
Q10:- A concave mirror of focal length 15cm forms an image of an object kept at a distance of 10cm from the mirror. Find the position, nature and size of the image formed by it.
Ans:- Here ,
f = -15cm
u=-10cm
v=?
1/v= 1/f -1/u (mirror formula)
1/v= 1/ (-15) -1/ (-10)
= 1/10 – 1/15
= 3/30 -2/30
=1/30
Therefore, v = 30cm
Thus, the image is formed at 30cm from the mirror.
As, v is positive, the image is virtual and erect
As, m = -v/u
= - 30/ (-10)
=3
Therefore, the size of the image is three times the size of the object.
11.HUMAN EYE AND COLOURFUL WORLD
Q1:- Name the optical phenomenon responsible for formation of RAINBOW?
Ans:- Refraction, internal reflection and dispersion of light.
Q2:- What is meant by scattering of light?
Ans:-Scattering is the bouncing off of electro-magnetic radiations by atoms and molecules of the medium through which they are propagating.
Q3:- Why different colours deviate through different angles on passing through a prism?
Ans:- This is because different colours have different wavelengths and glass has different refractive index for different wavelengths .
Q4:-Which phenomenon of vision is used in cinematography?
Ans:-Persistence of vision.
Q5:- The near point of the hypermetropic eye is 1metre.What is the power of the lens required to correct this defect. Assume that near point of the normal eye is 25cm.
Ans: - Since, the near point of the hypermetropic eye is1m (100cm), the lens used should be such that the rays of light starting from normal near point(25cm) appear to come from the near point of hypermetropic eye.
Thus,
u = -25cm
v =-100cm
1/f =1/v -1/u
f = uv/u-v
= (-25) x (-100)/ (-25) – (-100)
=100/3
=33.3cm
P = 100/f
= 100/33.3
= 3 D
Since the power is positive , lens must be convex.
Q6:-The far point of a myopic person is 80cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Ans:- Distance of far point ,x =80cm
P =?
For viewing distant objects, focal length of the corrective lens
f = - x = -80cm
P = 100/f
= 100/-80
=-1.25 D
The Lens is concave.
Q7:- Danger Signals are red in colour, why?
Ans:-Due to its longer wavelength, red colour is least scattered by fog or smoke.Thus, the red is visible in the same colour from large distances.
Q.8.Why do we have two eyes for vision and not just one?
Ans. (a) It gives a wider field of view.
(b).The ability to detect faint objects is enhanced with two eyes instead of one.
(c). Our eyes are separated by a few centimeters; each eye sees a slightly different image. Our brain combines the two images into one and thus provides a three-dimensional perception of the objects.
Q.9.What is persistence of vision?
Ans.The ability of an eye to continue to see the image of an object for a very short duration even after the removal of the object is called persistence of the vision. In human eye, vision persists for 1/16th of a second after removal of the object.
Chapter 12
Electricity
V.S.A Question (1 mark each)
1.What is the resistance of an ideal voltmeter and an ammeter?
Ans. Infinite and zero.
2.What is the value of charge on an electron in coulomb?
Ans. -1.6 x 10-19
3.Why is resistance more in combination of resistors?
Ans. In series combination of resistors, the effective length of the conducting path increases and as such resistance increases (R ∞l)
4.Name two special characters of a heater coil?
Ans. A heater coil should have (i) high resistivity (ii) high melting point.
5.What is the resistance of a connecting wire?
Ans. It is negligible, almost zero.
S.A.Q (2 marks each)
1. What is the difference between a resistor and resistance?
Ans. A resistor is an object where as resistance is its property due to which it obstructs the flow of electrons through it.
2.Electric current is flowing through a wire from west to east direction. What is the direction of motion of the conductor electrons in the wire?
Ans. From east to west as direction of electric current is opposite to the direction of flow of conduction electrons.
3.Why are the conductors of electric heating devices such as toasters and electric irons) made of an alloy rather than a pure metal?
Ans. It is because alloy is less affected by the rise in temperature than a pure metal. In other words alloys do not oxidise (or burn) easily at high temperature.
4.What will be the equivalent resistance R of two resistors R1 and R2 (i) connected in series and (ii) connected in parallel?
Ans. When connected in series
R=R1+R2
When connected in parallel
1/R=1/R1+1/R2 or R=(R1R2) /(R1+R2)
5.What will happen to current if the voltage across the circuit reduces to half its original value while the resistance of the circuit remains constant?
Ans. Current=Voltage/Resistance
If voltage becomes half its original value, the resistance remains the same, then current in the circuit will be reduced to half its original value.
SAQ (3 marks each)
1.A wire of resistance 5 ohm is bent in the form of a closed circle. What is the effective resistance between the two points at the ends of any diameter of the circle?
Ans. The length of the wire between two points at the ends of a diameter of a circle is half of the whole wire. The resistance of a conductor is directly proportional to its length.
Thus, the two resistance 5/2 Ω will be in parallel.
Let R be the effective resistance.
1/R=2/5+2/5
1/R=4/5
R=5/4=1.25 Ω
2.Calculate the effective resistance in the diagram given.
Ans. In this case resistance DA and AB are in series. DC and CB are also in series. But AD and AB together are in parallel to DC and CB together.
Thus, Resistance (DA + AB)=1+1=2Ω
and Resistance (DC + AB)=1+1=2Ω
Let Rp be the effective resistance, then (by parallel formula)
1/Rp=1/2+1/2
=(1+1)/2=2/2
Rp=1Ω
Thus, the combination has a resistance of 1 ohm.
3.Why does resistance of a conductor increase with increase in temperature?
Ans. When a metallic is heated the atoms in the metal vibrate with greater amplitude and frequency due to increase in temperature the thermal velocities of free electrons also increase. Therefore the numbers of collisions between free electrons and atoms increase. This increases the resistance of the conductor.
4.Why is it not advisable to handle electrical circuit with wet hands?
Ans. The resistance of dry skin human body is about 50,000Ω. When the skin is wet, the resistance is lowered to about 10,000Ω. If a person with wet hand touches the electrical circuit the current will flow suddenly due to less resistance. Therefore, it is advisable not to touch the electrical circuit with wet hands.
Long Answer Question (5 marks)
1.A dry cell should be used intermittently and not continuously. Explain why?
Ans. Hydrogen gas in the formed during the working of the dry cell. This gas in the form of bubbles forms an insulated layer around the carbon rod (i.e anode). As a result of this, the resistance of the cell is increased and hence the flow of charges in the cell is opposed. Ultimately, the dry cell stops working if used continuously. However, these bubbles of hydrogen gas are removed slowly by Mno2, which acts depolarizers. The dry cell can work if the bubbles of hydrogen gas around carbon rod are completely removed by Mno2. For this purpose time is required. So the dry cell should be used intermittently to provide sufficient time for the removal of hydrogen gas bubbles by manganese dioxide.
13.Magnetic effect of electric current
V.S.A.Q (1 marks)
1. What constitute the field of a magnet?
Ans. The space around a magnet within which its magnetic effect can be experienced, constitutes the (magnetic) field of the magnet.
2. What is meant by the following? A fuse is rated at 8 A?
Ans. It means that it burn if current exceeds 8A.
3.What is short circuiting in an electric supply?
Ans. Short circuiting in an electric supply occurs when the live wire touches the neutral wire.
4.What happens when a current carrying conductor is kept in a magnetic field?
Ans. It experience a force.
5.Are magnetic field lines open or closed curves?
Ans. They are closed curves.
6. What is the frequency of AC in India?
Ans. It is 50 Hz.
SAQ (2 marks)
1.Write down any two properties of magnetic field lines.
Ans. 1 It is directed from north pole to south-pole outside the magnet and inside the magnet it is vice-versa.
2.Two magnetic field lines never intersect each other.
2. What is electro-magnetic induction?
Ans. In reality it is the conversion of mechanical energy into electrical energy.
3.What is the role of each of the three pins in a power plug?
Ans. The thick pin at the top of a power plug is for earthing ,the live pin is on the left and the neutral pin is on the right of the power plug.
4. what are the two main precautions to be the taken while using an electric supply?
Ans. (i)Electric supply should be immediately switched off from the main switch in case a person touches a live wire or if there is a fire in the house.
(ii) Electric supply should also be switched off during natural calamities like earthquake, floods etc.
5.What is the difference between two circuits used in household electricity?
Ans. One of 15 ampere rating is used for higher power appliances and second of 5 ampere rating is used for bulbs, fans, etc. which are of lower power rating.
6.Two wires A and B suspended. These wires are connected in parallel with a battery as shown in figure. Will the distance of separation between the wires (i) remains the same or (ii) increases or (iii) decreases? Explain.
Ans. When wires are connected to battery in parallel, then the current in both the wires will attract each other, therefore the distance between the wire decreases.
SAQ (3 marks)
1.A circuit has a fuser of 5 A. What is the maximum number of 100 watt (220v) bulbs this can be safely used in the circuit?
Ans. Suppose x number of such bulbs can be used.
Power of one bulb =100 watt
Power of x bulb (p)=100 x X watts
Potential difference(v)=220 volts.
I=5 ampere
P=VI
= 100 x X= 220x5
X =220x5/100=11 bulbs
2.On what factors does the force experienced by a current carrying conductor placed in a uniform magnetic field depend?
Ans. The place in a uniform magnetic field depends on :-
(i)The length of the conductors(l).
(ii)The magnitude of current flowing through the conductor (l), and
(iii)The magnitude of the magnetic field of the conductor (B)
3.A fixed wire AB carries current I. An electron is moving parallel to the wire in which direction does the electron tend to move?
Ans. By right hand thumb rule, the magnetic field in the vicinity of wire is downward, perpendicular to the plane of the paper. The conventional direction of electrical current his opposite to the direction of motion of electron. By Fleming left hand rule the force on electron is always away from wire in the plane of paper; therefore, the electron will be deflected downward (away from the wire) in the plane of paper.
4.A cylindrical bar magnet is kept along the axis of a circular coil. Will there be a current induced in the coil if the magnet is rotated about the axis?
Ans. The magnetic field of a cylindrical magnet his symmetrical about the axis. As the magnet is placed along the axis of circular coil, there will be no induced current because the magnetic flux linked with the coil does not change due to rotation of the magnet.
LAQ (5 marks)
1.Answer the following
i.What is the phenomenon of electron magnetic induction?
ii.Which is the device used for producing current?
iii.What is the essential difference between AC generator and a DC generator?
iv.At the time short circuit, what happens to the current in the circuit?
v.Give the role of split ring in AC generator?
Ans. i) the phenomenon of electromagnetic induction is producing induced current in a coil due to relative motion between a magnet and the coil.
ii) The device used for producing current is generator
iii) The essential difference between an AC generator and DC generator is that AC generator has slip rings while the DC generator has a commutator.
iv)At the time of short circuit, the current in the circuit increases heavily.
v)The role of split ring is to reverse the direction of current through a circuit.
14.Sources of Energy
VSAQ (1 marks)
1.Name the two forms of energy usually at our homes?
Ans. Heat and electricity
2.Exposure to which component of solar radiation could be a health hazard?
And. Ultra violet radiation.
3.Name two forms in which solar energy manifests itself in oceans?
Ans. Tidal energy and ocean thermal energy
4.What are the sources of energy in nuclear fission and fusion?
Ans. The disappearance of certain mass ( m) in both the processes, fission and fusion. It appears as energy.
5.Which radiations of sunlight are used in heating a solar cooker?
Ans. Infra red radiations.
6.Name any two renewable sources of energy?
Ans. Solar energy and Geo-Thermal energy.
SAQ(2 marks)
1.Give any two peaceful uses of nuclear energy.
Ans. Nuclear energy can be used:
(i)for generating electricity
(ii)in the treatment of cancer
2.How is electrical energy obtained from nuclear reactors?
Ans.The large amount of heat produced during nuclear fission is treated to convert into steam. The steam is then used to drive turbines which are connected to electrical generators which convert it into electrical energy.
3.What is the purpose of glass sheet in solar heating devices?
Ans. Glass sheet has a property that permit the infra-red radiations of short wave length from the sun to get into heating device but does not allow IR radiations of longer wave length to leave the solar heating device.
4.Why is the use of charcoal discouraged although it is a better fuel than coal?
Ans. Because charcoal is prepared from destructive distillation of wood. So, for this purpose more and more trees would have to be cut down which causes deforestation. It affects the ecological balance of earth.
5.Can any source of energy be pollution free? Why or why not?
Ans. No source of energy can be perfectly pollution free but biomass energy, hydroenergy, wind energy, geothermal energy and solar energy is almost pollution free. If fossil fuel is allowed to burn in presence of excess of oxygen the pollution produced can be much reduced.
SAQ (3 marks)
1.If you could use any source energy for heating your food, which one would you use and why?
Ans. Fuel to be used should be easily accessible, should be easy to store and transport and should be economical. If we are in city area, LPG should be used since it does not produce pollution, is easily available and is economical.
In rural area, gobar gas or biogas should be used. It is almost free, has high calorific value and is pollution free. It is also renewable source of energy.
2.What is Bio-energy?
Ans. Bio-energy is the energy generated by biomass. Energy may be in form of fire, fuel oil, biogas, animal dung alcohol, charcoal or even human excreta. Fuels are derived from bio-mass. It is an indirect source of solar energy and is renewable source of energy.
3.Hydrogen gas has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG. Why or why not?
Ans. The by-product of hydrogen when used as a fuel and burnt is water while that of CNG are water and carbon dioxide gas. Water is an absolutely harmless by-product, however carbon dioxide in the environment causes green house effect leading to global warming. Hence, hydrogen can be called a cleaner fuel than CNG.
4.“Only a small part of the solar energy that strikes the upper regions of atmosphere, reaches the surface of the earth”. Discuss?
Ans. When the solar energy falls in the top surface of the atmosphere then some solar energy is reflected back into the space by the atmosphere, and the atmosphere also absorbs a lot of solar energy, for example most of the ultra violet rays are absorbed by the ozone layer. So the solar energy which reaches on the earth’s atmosphere is mainly in the form of heat rays (infrared rays) and visible light, which is a small part of the solar energy.
5.What is geo-thermal energy? What are its limitations?
Ans. Geo-thermal energy is the heat of the earth and is the naturally occurring thermal energy found within rock formations and the fluids held within those formations. Geo-thermal energy is on of those few sources that do not come directly or indirectly from the solar energy.
Limitations
i)Goe-thermal hot spots are scattered and usually some distance away from the areas that need energy.
ii)The overall power production has lower efficiency (about 15%) as compared to that of fossil fuels (35% to 40%)
iii)Though as a whole geothermal energy is inexhaustible, a single bore has a limited life span of about 10 yrs.
iv)Noise pollution is caused by drilling operations at geo-thermal sites.
LAQ (5marks)
1.What are environment consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Ans. The demand of energy consumption is increasing day to day. Exploiting any source energy may disturb the environment in one-way or other. For example getting energy from fossil fuel may cause lot of pollution in air. Getting energy from nuclear fission may create problem of disposal of nuclear waste.
Steps for reducing energy consumption should be such that we get maximum energy from least fuel. For this:
i.Under the given situation technology utilized should be the best possible. For example. Using smokeless chulhas should be preferred to traditional chulhas.
ii.Energy should be extracted by most economic method under the given situation. Where as energy extraction by solar cells may be useless in big towns due to cost factor, it may be indispensable for artificial satellites.
iii.Wastage of energy should be strictly avoided. Energy saved is equal to energy produced.
iv.Sources of energy should be such that it causes least damage to environment.
15.Our environment
VSAQ (1 marks)
1.Would you eat animals or plants to get more calories of heat?
Ans. We should eat plants to get more calories of heat.
2.What will happen if we kill all the organisms in one tropic level?
Ans.If we kill all the organisms in one tropic level, unbalances are created in the food chain.
3.Write an aquatic food chain?
Ans. Phytoplankton ton zooplanktonfishseal
4.Why ozone layer is called radiation belt?
Ans. Because it checks the entry of high energy UV-radiations of sunlight in the earth’s atmosphere.
5.What is detritus?
Ans. Dead organic matter.
6.Explain why the practice of serving tea in Kulhads (disposable cups made of clay) on trains has been discontinued.
Ans. Because the use of a lot of clay for making millions of Kulhads daily lead to the loss of fertile top soil in the fields.
7.Write the full form of CFC. Give its one harmful effect.
Ans. The full form of CFC is Chloroflouro-carbons. Chloroflouro carbons are damaging the ozone layer in the upper atmosphere.
SAQ (2 marks)
1.How is the ozone formed?
Ans. Ozone is formed high up in atmosphere by the action of ultraviolet radiation on oxygen gas as follows.
O2 O + O
O2 + O O3 (ozone molecule)
Oxygen molecule.
2.State any two practices which can help in the protection of our environment.
Ans. i. Disposal of waste after its separation as biodegradable and non-biodegradable waste material
ii. Judicious use of unleaded petrol, alternate sources of energy. Engines of vehicles should also be properly tuned and serviced so that vehicles run efficiently.
3.Give two ways in which biodegradable substance would affect the environment.
Ans. i. Stink- Within a day or so waste biodegradable substances begin to stink and produce foul gases.
` ii. Pests and Pathogens- the decaying biodegradable substances become breeding places of many pests. Because of being waste in origin they often contain pathogens.
4.Which of the following are biodegradable and which non-biodegradable?
Glass bottle, Paper, Ball point pen refill, DDT, Wheat, Cake, Wood, Polythene bag, Cotton, Grass, Vegetable peels.
Ans. i. Biodegradable: Paper, Wheat, Cake, Wood, Jute bag, Cotton Cloth, Grass, Vegetable peels.
ii. Non- biodegradable: Glass bottle, Ballpoint pen refill, DDT, Polythene bag.
5.What is ‘Ten percent low’?
Ans. Ten percent low is an enunciation given by Lindeman (1942) that states that only 10% of energy contained in a lower tropic level, the remaining 90% being lost in transfer and respiration of the later.
SAQ (3 marks )
1.How is solar energy introduced into the ecosystem?
Ans. The green plants have a mechanism for trapping solar energy with the help of their green pigment called chlorophyll. The green plants after trapping the solar energy, convert it into chemical energy whish is stored as carbohydrates in the plants. Thus the initial point where energy from the environment enters into the living components of ecosystem (like plants and animals) is the process of preparation of food by green plants through photosynthesis.
2.How can you help in reducing the problems of waste disposal?
Ans. 1. Recycling of wastes.
2. Reduction at source.
3. Better management.
4. Vermi-composting.
` 5. Use of eco friendly products such as disposable paper cups in place of plastic cups,
Chapter 16
Management of Natural Resource
VASQ(1 marks)
1. Write utility of construction of dam and reservation.
Ans. Regular supply of water for irrigation, controlling floods and generating electricity.
2. Define biodiversity.
Ans. It refers to totality of genes, species and ecosystem of a region, eg -Forest.
3. Why was Ganga Action plan launched?
Ans. To restore quality of water in the Ganga. It was very poor due to pollution.
4. What are the three R’s to save environment?
Ans. Reduce, Recycle and Reuse.
5.The presence of which organism indicates the pollution index of water body?
Ans. The presence of coli form group of bacteria indicates the pollution index of water body.
6. Name the river with which Sardar Sarovar Dam is associated.
Ans. The river with which Sardar Sarovar Dam is associated is Narmada.
7. Give one criticism about large dam.
Ans. Large dams consume large amount of public money without the generation of proportionate benefits.
SAQ(2 marks)
1. Mention two ways in which water harvesting can be undertaken.
Ans. i. Capturing sum off water from roof-tops.
ii. Capturing sum off water from local catchments.
2. Why reuse better than recycling?
Ans. Reuse is better than recycling because the process of recycling uses some energy. In the reuse strategy we simply use things again and again.
3. What would be advantages of exploring resources with short terms aims?
Ans. Exploring resources with short-term aims provide immediate advantage that meet current basic human need.
4. How can you as an individual contribute or make a difference to management of (i) water resources and (ii) Coal and petroleum?
Ans.(i) Running water will not be used for brushing teeth or taking bath. Water will be taken in a mug and bucket for these purpose to prevent wastage.
(ii) Switch off unnecessary lights and fans etc. and use bicycle to cover short distances instead of a scooter or car.
5. Write down any two consequences of deforestation.
Ans. i. Change in climate and global warming
ii. Soil erosion and floods.
6. Name any two endangered plant and animal species.
Ans. Endangered plant species- Pitcher Plant and Snow orchid.
Endangered animal species- Indian wild Ass and Great Indian Rhinoceros
SAQ ( 3marks)
1. Can you suggest some changes in yours school whish would make it environment friendly?
Ans. i. School busses should be run on CNG instead of diesel.
ii. Trees should be planted along the school boundary.
iii. The fallen leaves of trees should be collected and made into compost. This compost can be used in school garden.
2. What are the causes of pollution of Ganga river?
Ans. 1. Dumping of garbage and untreated swage from all the towns and cities on the banks of the ricer.
ii. Bathing by millions of people, washing clothes, animals and vehicles in the river water.
iii. Immersion of ashes or even dead bodies in the performance of rituals.
iv. Releasing chemical effluents from industries directly into the river water.
3. Find out the traditional system of water-harvesting/ management.
Ans. Traditional system of water harvesting/ management.
i. Diversion of water flowing in streams into man made channels to cater to the demand of the people
ii. Collection of water in ponds.
iii. Contraction of dams.
4. Why is dependence of man or nature greater than that of any other organism?
Ans. Man’s dependence on nature is greater than that of any other organism because he:
i.Has developed curiosity for more comforts and security.
ii.Consumes large amount of material and energy.
iii.Has developed a new bond of socio-economic environment which consists of things developed by man through his tools and techniques.
5.What is Chipko Andolan?
Ans. This movement was launched by people of Reni in Garhwal. It was spearheaded by Sundar Lal Bahuguna. The Chipko Andolan (Hug the trees Movement) was the result of a grass- root level effort to end the alienation of people from their forests. The movement originated from an incident in a remote village called Reni in Garhwal during the early 1970’s The women of the village reached the forest and clasped the tree trunks to trees and felling it. Thus thwarted the constructor had to withdraw.
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