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#### Question 1:

Who coined the term protoplasm for living matter?

The term protoplasm was coined by J.E. Purkinje in 1839.

#### Question 2:

Which plant group is called 'amphibians' of the plant world?

Organism belonging to the division Bryophyta are referred to as amphibians of the plant kingdom.

#### Question 3:

Find the initial velocity of a car which is stopped in 10 seconds by applying brakes. The retardation due to brakes is 2.5 m/s2.

Retardation due to brakes = 2.5 m/s2

$\therefore$
a = $-$2.5 m/s2

Time taken in stopping = 10 seconds

Final velocity of car = 0 m/s

Let the initial velocity = u

Using the first equation of motion, = u +at

Hence, the initial velocity of the car is 25 m/s.

#### Question 4:

Do action and reaction act on the same body or different bodies? How are they related in magnitude and direction?  Are they simultaneous or not?

According to Newton's third law, for every action, there is an equal and opposite reaction. The action and reaction forces act on different bodies. For example, if a ball is thrown to a wall. The ball applies an action force on the wall, in return the wall applies the reaction force on the ball. Hence, the action force acted on the wall but the reaction force acted on the ball.

Action and reaction forces are equal in magnitude but opposite in direction. Yes, they are simultaneous in nature as they are applied at the same instant but on different bodies.

#### Question 5:

Why do plants and animals possess different types of tissues?

Animals and plants show different modes of nutrition. Animals are heterotrophic organisms, whereas plants are autotrophic organisms. Moreover, animals show locomotion but plants are stationary organisms. The differences in the mode of nutrition and extent of locomotion are the reason for the presence of different tissues in animals and plants.

#### Question 6:

Give two reasons to justify that:
(i) Water is a liquid at room temperature.
​(ii) An iron almirah is a solid.

(i) Water is a liquid at room temperature because:
a) It has a definite volume but no definite shape.
b) It takes the shape of the container.

(ii) An iron almirah is a solid at room temperature because:
a) It has a  definite shape and volume.
b) It is rigid.

#### Question 7:

What is meant by atomicity? What is the atomicity of the following?
​(i) Oxygen (ii) Ozone (iii) Neon (iv) Sulphur

Atomicity is the number of atoms of an element present in one molecule of that element. For eg., there are 2 atoms of hydrogen present in H2 molecule. So, its atomicity is 2.

Atomicity of following elements is:
(i) There are 2 atoms of the oxygen present in the oxygen(O2) molecule. So, its atomicity is 2.
(ii) There are 3 atoms of the ozone present in the ozone(O3) molecule. So, its atomicity is 3.
(iii) There is 1 atom of the neon present in the neon(Ne) molecule. So, its atomicity is 2.
(iv) There are 8 atoms of the sulphur present in the sulphur(S8) molecule. So, its atomicity is 8.

#### Question 8:

All the gases form cathode rays and anode when electricity is passed through them:
(i) What does the formation of cathode rays tell us about the atoms?
(ii) What does the formation of anode rays tell us about the atoms?

When electricity is passed through the gases, they split into ions:
(i) Ions having negative charge move towards the positively charged cathode, these negatively charged ions are known as electrons.

(ii) Ions having positive charge move towards the negatively charged anode, these positively charged ions are known as protons.

#### Question 9:

When a ball is thrown vertically upwards, it goes through a distance of 19.6 m. find the initial velocity of the ball and the time taken by it to rise to the highest point. (Acceleration due to gravity, g = 9.8 m/s2​)

Distance travelled by the ball = 19.6 m

Acceleration due to gravity = ​g = 9.8 m/s2

Let the initial velocity of the body = u

Final velocity of the ball = 0 m/s

Time taken by the ball to reach to the highest point = t

Using the third equation of motion, ${v}^{2}={u}^{2}-2gs$

Now, using the first equation of motion for the ball thrown upward, u - gt

Time taken by the ball to reach the highest point = 2 s

And the initial velocity of the ball, u = 19.6 m/s

#### Question 10:

The hanging bob of a simple pendulum is displaced to one extreme position B and then released. it swings towards centre position A and then to the other extreme position C. In which position does the bob have:
(i) maximum potential energy?
(ii) maximum kinetic energy?

A hanging bob swings around its mean position from one extreme to another extreme position.

(i) The bob has the maximum potential energy at the extreme positions. In the given case, the bob will have maximum potential energy at B and C positions. Because the velocity of the bob becomes zero at the extreme positions, that's why at extremes whole of the energy becomes potential energy.

(ii) At the mean position, the velocity of the bob is maximum as all of the potential energy gets converted into kinetic energy. Hence, at the mean position A, the bob will have the maximum kinetic energy.

#### Question 11:

Figure X shows a trace of a sound wave produced by a particular tuning fork.
(i) On the graph given in Figure Y, draw a trace of the sound wave which has a higher frequency than that shown in Figure X.
​(ii) On the graph paper shown in Figure Z, draw a trace of the sound wave which has a larger amplitude than that shown in Figure X

(i)

(ii)

#### Question 12:

What are the consequences of the following conditions?
(i) A cell having higher water concentration than the surrounding medium.
(ii) A cell containing lower water concentration than the surrounding medium.
(iii) A cell having equal water ​concentration to its surrounding medium.

(i) A cell having a higher concentration of water than the surrounding medium will gradually lose water through exosmosis and can become flaccid or plasmolysed.

(ii) A cell having lower water concentration than the surrounding medium will gain water through endosmosis and can become turgid or can burst.

(iii) A cell having equal water concentration to its surroundings will neither lose nor gain water.

#### Question 13:

In a cluster of hutments, many people are suffering from malaria. Mention the unhygienic conditions that must be prevailing in that locality. How does a doctor confirm malaria? Explain the methods of prevention of malaria.

The unhygienic conditions that lead to malaria in a cluster of hutments are as follows:
1. Stagnant water may be present in the vicinity of the hutments which can serve as breeding ground for mosquitoes.
2. The sewage drains may be open which can lead to uncontrolled growth of mosquitoes.
3. Undulating surface of the canvas sheet which are generally used in hutments, hold rainwater that contributes to the growth of mosquitoes.

A doctor can confirm malaria by performing a blood test to detect the malarial parasite.

Malaria can be prevented by taking the following measures:
1. Breeding grounds such as swamps and puddles should be destroyed.
2. Insect repellents can be used to reduce mosquito bites.
3. Chemical insecticides can be used to kill mosquitoes.

#### Question 14:

Why is ozone layer called ozone umbrella/shield? What would be the effects on widening of ozone hole?

Ozone layer refers to the region of the Earth's atmosphere, which has a relatively higher concentration of ozone. This layer is also called ozone layer/umbrella because it acts as a shield and prevents the propagation of harmful ultraviolet radiation to the Earth's surface.

The widening of the ozone hole can have following consequences:
1. The chances of skin cancer will be increased.
2. The overall crop yield will be profoundly decreased.
3. The populations of zooplanktons and phytoplanktons will be severely reduced.

#### Question 15:

Define green revolution, what are the common objectives of crop improvement?

Green revolution is described as the exponential increase in the food grain yields, which occurred during the 1970s.

The common objectives of crop improvement are as follows:
1. Improvement in crop yield
2. Improvement in nutritive values of the crop
3. Development of crops that are resistant to pests and insects
4. Development of crops that are adapted to a wide range of climatic conditions

#### Question 16:

(i) What is fractional distillation? What is the use of fractionating  column in fractional distillation?
​(ii) Draw a labelled diagram of the fractional distillation apparatus used for separating a mixture of alcohol and water.

(a) Fractional distillation: It is a process of separation of a chemical mixture whose components have different boiling points.
This process is used for separating mixtures like water and ethanol, or in production of gasoline from crude oil.
A fractionation column is used to separate the liquids according to the order of their vaporization so that they get separated as they are vaporized.

(b)  Diagram of the fractional distillation apparatus used for separating a mixture of alcohol and water:

#### Question 17:

(i) Define mole. What are the two things that a mole represents?
​(ii) What weight of each element is present 1.5 moles of sodium sulphite, Na2SO3? (Atomic masses: Na = 23u; S = 32 u; O = 16 u.)

(i) A mole is a unit of measurement used to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon 12.
A mole represents:
a) One mole of any substance contains 6.022$×$1023 particles. This means that one-mole atom, molecule or ions of any substance contain 6.022$×$1023 atoms.
b) One mole of a substance is that quantity in number having a mass equal to its atomic or molecular mass in grams.

(ii)
For 1 mole of sodium sulphite, Na2SO3
The atomic mass of sodium, Na = 23 g
for 2 atoms of sodium, the atomic mass of sodium = 2×23 g
= 46 g
The atomic mass of sulphur, S = 32 g
The atomic mass of oxygen, O = 16 g
for 3 atoms of oxygen, the atomic mass of oxygen = 3×16 g
​                                                                         = 48 g
For 1.5 mole of sodium sulphite, Na2SO3, the weight of each element is,
For sodium, weight = 1.5×46 g
= 69 g
For sulphur, weight = 1.5×32 g
= 48 g
For oxygen, weight = 1.5×48 g
= 72 g

#### Question 18:

(a) What do you understand by the terms "balanced forces" and "unbalanced forces"? Explain with examples.
​(b) What type of forces - balanced or unbalanced - act on a rubber ball when we press it between or hands? What effect is produced in the ball?

(a) Balanced forces: When two or more forces act on an object but are not able to change the state of rest or of motion of that object, the forces are called balanced forces. The resultant of balanced forces is always zero, so they can not produce any acceleration in the object.

Example: If more than two people push a box from different sides and the box does not move, that means the forces are balanced.

Unbalanced forces: When two or forces act on an object and are able to change the state of rest or of motion of that object, the forces are called unbalanced forces. Unbalanced forces always have a resultant and can produce an acceleration in the object.

Example: If few people push a box from different directions and the box starts moving then the forces acting on the object are unbalanced forces.

(b) When we press a ball between our hands, then the forces acting on the ball are balanced, as they do not cause any motion to the ball. When we press the ball between our hands, the ball gets compressed or deformed. The balanced forces change the shape of the ball.

#### Question 19:

(a) Explain why a cricket player moves his hands backward while catching a fast cricket ball.
​(b) A 150 g ball, travelling at 30 m/s, strikes the palm of a player's hand and is stopped in 0.05 second. Find the force exerted by the ball on the hand.

(a) A player moves his hands backward to reduce the effect of the force of fast cricket ball on his hands. A fast-moving ball has a high momentum, and when the player catches the ball, the momentum of the ball changes to zero in a very short span of time. That's why it hits his hands. Hence, to reduce the effect of the force, the player pulls his hands back so that he can increase the time in which the momentum of the ball falls to zero. By increasing the time, rate of change of momentum decreases which impacts less force on the hands of the player.

(b) Mass of the ball = 150 g = 0.15 kg

Initial velocity of the ball = 30 m/s

Final velocity of the ball = 0 m/s

Time taken by the ball to stop = 0.05 s

Force exerted by the ball on the hand of the player =  Rate of change of momentum of the ball =

Force

Hence, the force exerted by the ball on the hand of the player is 90 N.

#### Question 20:

In brief, state what happen when
(i) Dry apricot are left for some time in pure water and later transferred to sugar solution.
(ii) A red blood cell is kept in concentrated salt solution.
(iii) The plasma membrane of a cell breaks down.
​(iv) Golgi apparatus is removed from the cell.

(i) In pure water, dry apricots will show endosmosis and absorb water to become swelled. These apricots will lose water through exosmosis in a sugar solution.

(ii) In a concentrated salt solution, a red blood cell will gradually lose water and shrink in size.

(iii) The breakdown of the plasma membrane of a cell will result in the death of the cell and all the cytoplasmic contents will be scattered.

(iv) Boiled Rheo leaves will not be able to show osmosis. These leaves will not perform endosmosis or exosmosis when a drop of sugar is used on these leaves.

(v) Golgi apparatus is required by the cell for different processes such as protein modification and protein sorting. The removal of the Golgi apparatus from the cell will affect these functions.

#### Question 21:

Explain the general characters of phylum Arthropoda. Give one example of following classes (i) Crustacea; (ii) Myriapoda; (iii) Insecta; (iv) Arachnida.

The general characteristics of phylum Arthropoda are as follows:
1. The animals of this phylum show bilateral symmetry, triploblastic origin and metameric segmentation.
2. The body segments are generally classified into two (cephalothorax and abdomen) or three (head, thorax and abdomen) regions.
3. Sexual dimorphism is observed in most of the organisms.

(i) Daphnia (water flea) belongs to the class Crustacea.

(ii) Julus (millipede) is an organism that belongs to the class Myriapoda.

(iii) Melanopus (grasshopper) has been classified under the class Insecta.

(iv) Sarcoptes (itch-mites) belong to the class Arachnida.

#### Question 22:

In an experiment, 4.90 g of copper oxide was obtained from 3.92 g of copper. In another experiment, 4.55 g of copper oxide gave, on reduction, 3.64 g of copper. Show with the help of calculations that these figures verify the law of constant proportions.

The law of constant proportion states that in a compound, the element is always present in definite proportions by mass.

$2\mathrm{Cu}+{\mathrm{O}}_{2}\to 2\mathrm{CuO}$

4.90 g of copper oxide was obtained from 3.92 g of copper. Therefore, the percentage of copper in 4.90 g of copper oxide will be,

Now, 3.64 g of copper is obtained from 4.55 g of copper oxide. So, the percentage of copper in this sample of copper oxide will be,

Thus, we can see that the percentage of copper in both samples of copper oxide is the same. This means that copper and oxygen always combine in a fixed ratio by mass to form copper oxide. Thus, the law of constant proportions is satisfied here.

#### Question 23:

The atomic species A and B have different number of protons but the same number of nucleons. On the other hand, the atomic species X and Y have the same number of protons but different number of nucleons.
​Which pair is an example of isobars? Why?

​Any member of a group of atomic or nuclear species all of which have the same mass number that is the total number of protons and neutrons, is known as isobars.
Protons and neutrons i.e. the atomic mass of the element is known as nucleons.

Therefore, species A and B have different protons but the same number of nucleons. So, they are isobars.
While X and Y have the same number of protons but a different number of nucleons, so they are isotopes.

#### Question 24:

Name the energy transfers which occur when:
(i) an electric bell rings
(ii) someone speaks into a microphone
(iii) there is a picture on a television screen
​(iv) a torch is on

(a) When an electric bell rings, the electrical energy gets converted into sound energy.

(b) When someone speaks into a microphone then sound energy gets converted into electrical energy.

(c) When there is a picture on television the electrical energy gets converted into light energy.

(d) When a torch is on, the chemical energy of the cell of the torch gets converted into light energy.

#### Question 25:

A coin and a peice of paper are dropped simultaneously from the same height. Which of the two will touch the ground first? What will happen if the coin and the peice of paper are dropped in vacuum? Give reasons for your answer.

The coin will touch the ground first, because the weight of the coin is much larger in comparison with the piece of paper, so it will feel less air resistance. That's why the coin will fall fast and will reach the ground first. The piece of paper being lighter will face the air resistance while coming down, due to that it will take time to reach the ground.

If both the coin and the piece of paper are dropped simultaneously in a vacuum then both will touch the ground at the same time, because there will not be any air resistance. So, they will fall with the same acceleration and the time taken by both of them would be the same.

#### Question 26:

What will happen if (a) Bone is dipped in hydrochloric acid (HCI); (b) Bone is dried?

(a) A bone that is dipped into hydrochloric acid will gradually lose its inorganic matter and become soft and brittle. The bone, however, does not melt because it also has organic component such as collagen that make up the bone matrix.

(b) The drying of a bone will destroy its organic matter, but its mineral matter will not be effected.

#### Question 27:

After recovering from infection of ringworm, Reena thought that all fungi are harmful for human kind, as these spoil food and cause various diseases. But her elder sister told him that not all fungi are harmful, some are quite useful such as in making bread, vitamins, Medicines (antibiotics) and in decomposing organic wastes.
(i) Name any fungus which is used in bread making.
(ii) Name any fungus which is the source of some medicine.
​(iii) What ecological benefit is shown by fungi?