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Q:

Convert 573 K into Celsius.

A:
273 K = 00C
573 K = 573 – 273 0C
= 300 0C
Q:

Classify the following as physical or chemical changes

(a) Dissolving common salt in water.
(b) Burning of Sugarcane.
(c) Burning of candle.
(d) Purification of metal.

A:
(a) Physical change
(b) Chemical change
(c) Chemical change
(d) Chemical change
Q:

Identify the form of energy in the following:
(i) Compressed spring.
(ii) Flowing river water.

A:

(i) In compressed spring, the energy is stored by applying a non zero external force. By vertue of the rest position, this will corresponde to the Potential Energy.
(ii) In flowing of river water, water is flowing by vertue of its motion, so this energy will corresponde to Kinetic Energy.

Q:

How many minimum forces are required to keep a body at equilibrium?

A:
Minimum two forces are required to keep a body at equilibrium.
Q:

What is a molecule?

A:
A molecule is a group of two or more atoms bonded together chemically. It is the smallest particle of an element or a compound that is capable of an independent existence and shows all the properties of that substance.
Q:

What is green house effect?

A:
The earth reflects the heat rays received from the sun. The phenomenon of preventing the escape of these heat rays from the earth is called green house effect.
Q:

Name the group of the following organisms:
(a) Sponges
(b) flatworms

A:
(a) Sponges = Porifera
(b) Flatworms = Platyhelminthes
Q:

Define biosphere.

A:
The life-supporting zone of the earth where life is possible due to interaction of the atmosphere, hydrosphere and lithosphere is called biosphere.
Q:

Name the constituents of the blood.

A:
Blood consists of a fluid called plasma which contains proteins, salts, hormones and cells like red blood cells and white blood cells.
Q:

The speed-time graph for a car is given as follows:

Calculate:
(a) Distance travelled in 3 seconds.
(b) Acceleration.

A:

(a) Distance travelled in 3 s = area of ∆ ABC

= 6 m
(b) Acceleration = change in speed/time taken

a = (6-0)/3

a = 2 m/s2

Q:

Write distribution of electrons in sodium. What will be the valency of sodium?

A:
Atomic number of sodium = 11
Electronic distribution in sodium is given as under:

K shell

L shell

M shell

2

8

1

Valency of the sodium = 1 (one).

Q:

A solution contains 20 g of sugar in 240 g of water. Calculate the concentration in terms of mass by mass percentage of the solution.

A:
Mass of sugar in water = 20 g

Mass of water = 240 g

Total mass of solution = 240 + 20 = 260 g

Mass percentage of sugar x 100

= (20 x 100)/260

= 7.7 %

Q:

Calculate the number of particles in each of the following:

(a) 7g of the nitrogen atoms.
(b) 0.5 mole of carbon dioxide

A:

(a) Atomic mass of nitrogen = 14 u

Thus no. of particles in 14 g = 6.023 x 1023

No. of particles in 1 g =6.023 x 1023/14

No. of particles in 7 g of nitrogen atoms =

No. of particles in 7 g of nitrogen atoms = 3.012 x 1023

(b) 1 mole of carbon dioxide = 6.023 x 1023 particles

0.5 moles of carbon dioxide = particles

= 3.012 x 1023 particles

Q:

Is a cyclist moving around a circular path with uniform speed moving with a uniform acceleration also? Give reasons to support your answer.

A:
A cyclist moving around a circular path with uniform speed does not move with the constant acceleration. It is because in a circle the direction of its motion keeps changing which causes change in the direction of its velocity leading to change in the acceleration.
Q:

Which cell organelles are called powerhouses of the cell? Why?

A:
Mitochondria are called the powerhouses of the cell because these help in the release of energy from the food in the form of ATP which is used for the various activities of the cell.
Q:

How are the winds caused?Out of syllabus

A:
Winds are caused due to uneven heating of the atmosphere in different regions of the earth. When air at a place is heated by radiations from the heated land or water, the hot air rises. This creates region of low pressure. In order to fill that space the cold air from the nearby places moves to that place. This movement of the air causes wind.
Q:

Name the following:
(a) Tissue that stores fat in our body.
(b) Tissue that connects muscle to bone in animals.
(c) Tissue that forms the animal skin
(d) Tissue that forms the coconut husk.

A:
(a) Adipose tissue
(b) Tendon
(c) Squamous epithelium
(d) Sclerenchyma
Q:

Write differences between a prokaryotic and a eukaryotic cell.

A:

Prokaryotic cell

Eukaryotic cell

(a) Small in size.

(a) Generally large in size.

(b) Nuclear region is not surrounded by a nuclear membrane and is called nucleoid and contains only a single chromosome.

(b) Nuclear region is surrounded by a nuclear membrane and contains more than one chromosome.

(c) Membrane bound cell organelles are absent.

(c) Membrane bound cell organelles are present.
Q:

Explain the following:
(a) Water droplets are seen on the glass containing ice-cold water.
(b) We should wear cotton clothes in summer.
(c) Water kept in the earthen pot becomes cool during summer.

A:
(a) Water vapour present in the air comes in contact with the outer surface of the glass containing ice, condenses on it to form water droplets.
(b) During summer, we perspire more sweat. Cotton, being a good absorber of water absorbs the sweat and exposed to it to the atmosphere for easy evaporation. The sweat takes body heat to evaporate and hence we feel cool.
(c) Earthen pots have pores in them in which water enters. During summer, the water present in the pores evaporates fast by taking heat from the water present in the earthen pot. Due to this water kept in an earthen pot becomes cool during summer.
Q:

A hammer of mass 500 g, moving at 50 m/s, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. What is the force of the nail on the hammer?

A:

Mass of the hammer (m) = 500 g = 0.5 Kg
Initial velocity of the hammer (u) = 50 m/s
Final velocity of the hammer (v) = 0

Time taken to stop the hammer (t) = 0.01 s

Acceleration on the hammer (a) = (v-u)/t

= (0-50)/0.01

= -5000 m/s2

Force exerted by the nail to stop hammer (F) = m x a

F = 0.5 x 5000

F = 2500 N

Q:

Describe Bohr’s model of atom with the help of a sketch.

A:
The main postulates of Bohr’s model of atom are as follows:
Only certain special orbits called discrete orbits of electrons are allowed inside the atoms.
While revolving in discrete orbits the electrons do not radiate energy.

Q:

A car moving with a speed of 12 m/s comes to rest when brakes are applied to produce an acceleration of 3 m/s in opposite direction. Calculate:
(A) the car to come to rest.
(b) Distance travelled before coming to rest.

A:

(a) Here initial velocity (u) = 12 m/s
Final velocity = 0 (as the car has come to rest)
We know, acceleration =

time = 12/3

time = 4 s

(b) Distance travelled before coming to rest =

=

= 48 + 24

= 72 m

Q:

Give reasons for the following:
(a) A cricketer pulls his hands while catching a ball?
(b) Safety belts are worn while driving.
(c) the base of a dam is made broader.

A:
(a) A cricketer pulls his hands while catching a ball in order to increase the time during which the high velocity of the moving ball decreases to zero. This causes decrease in the acceleration of the ball and thus the force or the impact of the ball on the hands of the cricketer decreases.
(b) With the application of brakes, the car slows down but our body tends to continue in the same state of motion because of its inertia. This may cause injury to us by collision with the panels in front. Safety belts slow down our forward motion and thus prevent such accidents.
(c) The base of the dam is made broader in order to increase the area of the base so that the pressure on the base is decreased and hence they can bear a large amount of force.
Q:

Suggest characteristics that a farmer would look before selecting crop variety for farming?

A:
Characteristics that a farmer would look before selecting crop variety for farming are as follows:
· The variety should be high yielding.
· It should be resistant to biotic (pests, etc) and abiotic (temperature) factors.
· It should have shorter duration of maturity.
· It should be able to yield desirable products.
Q:

Explain briefly Rutherford’s experiment, its observations and conclusions.

A:
Rutherford selected a gold foil of about 1000 atoms thick. He bombarded it with the high energy alpha particles.
Observations:
(a) Most of the fast moving alpha particles passed straight through the gold foil.
(b) Some of the alpha particles were deflected by the foil by small angles.
(c) One out of every 12000 particles rebound back.
Conclusions:
(a) Most of the space inside the atom is empty.
(b) Positive charge of the atom occupies very little space inside the atom.
(c) Mass of the atom and all the positive charge were concentrated in a very small volume within the atom.

Q:

Differentiate between a solution, a colloid and a suspension.

A:

Solution

Suspension

Colloid

(a) It is a homogeneous mixture.

(a) It is heterogeneous mixture.

(a) It is heterogeneous mixture.

(b) The particles of a solution cannot be seen with the naked eye.

(b) The particles of a suspension can be seen with the naked eye.

(b) The particles of a colloid cannot be seen with the naked eye.

(c) These do not show tyndall effect.

(c) These do not show tyndall effect.

(c) These show tyndall effect.

(d) The particles of a solution cannot be separated by filtration.

(d) The particles of a solution can be separated by filtration.

(d) The particles of a colloid cannot be separated by filtration.

Q:

(a) Define the universal law of gravitation.
(b) What is the difference between g and G.
(c) The mass of an object is 40 Kg. What is its weight on earth and on moon?

A:
(a) According to the universal law of gravitation, every object in the universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
(b)

g

G

(i) It is the acceleration produced due to the gravitational force.

(i) It is the universal gravitation constant.

(ii) Its value is not constant. Its SI unit is m/s2.

(ii) Its value is constant everywhere in the universe. Its SI unit is Nm2/Kg.

(c) The mass of the object (m) = 40 Kg

Weight of the object on the earth (W) = m x g

W = 40 x 9.8

W = 392 N

Since the acceleration due to gravity on the moon is 1/6th of the acceleration due to gravity on the earth, weight of the object on the moon = m x g/6

= (40 x 9.8)/6

= 65.33 N

Q:

(a) What types of waves are the sound waves?
(b) How are the light waves different from sound waves?
(c) Give reasons for:
(i) Why we hear different sounds from different sources?
(ii) Why do we hear sound of the thunder a few seconds after we see the lightning?

A:
(a) Sound waves are the longitudinal mechanical waves.
(b)

Light waves

Sound waves

(i) Light waves travel in the form of transverse waves.

(i) Sound waves travel in the form of longitudinal waves.

(ii) These do not require any medium for their propagation.

(ii) These require a medium for their propagation.

(c) (i) We hear different sound from different sources because of the differences in the properties like pitch, amplitude and wavelength of the sound waves coming from different sources.

(ii) Speed of light is more than the speed of sound due to which light travels faster than sound and hence we are able to hear the sound of the thunder a few seconds after we see the lightning.
Q:

Differentiate between:
(a) Striated and unstriated muscles.
(b) Xylem and phloem.

A:
(a)

Striated muscles

Unstriated muscles

(i) The cells are long, cylindrical, and multinucleate.

(i) The cells are spindle shaped and uninucleate.

(ii) These move according to our will.

(ii) These cannot move according to our will.

(iii) These have striations on them e.g. muscles found in our limbs.

(iii) These do not have striations e.g. muscles present in alimentary canal.

(b)

Xylem

Phloem

(i) These consist of tracheids, vessels, xylem parenchyma.

(i) These consist of sieve tubes, companion cells, phloem fibres and parenchyma.

(ii) These help in the transport of water and minerals.

(ii) These help in the transport of food.

(iii) Materials move in one direction.

(iii) Materials can move in both the directions.

Q:

Differentiate between an animal cell and a plant cell diagrammatically.

A:

Q:

Write the name of two organisms, which take part in the nitrogen fixation.

A:
Rhizobium and Azotobacter.
Q:

What is meant by balanced forces?

A:
Forces are called balanced forces act on a body and nullify each other such that the resultant of these forces is zero.
Q:

In which of the following conditions, do you think the long term effects on health are likely to be most unpleasant if a person gets:
• Jaundice
• Cold
• Acne
Give reasons in support of your answer.

A:

If a person gets jaundice, the effect on his/her health will be most unpleasant.

In jaundice, the functioning of the liver is hampered resulting into impaired general health.
Q:

Why is the motion of Satellites around their planets considered an accelerated motion?

A:
Satellites revolve around their planets in almost circular orbits with constant speed. Thus, during their motion, the speed remains constant, while the direction of motion changes continuously. As a result, there is a change in their velocity. Therefore, the motion of satellites around their planets is considered as accelerated motion.
Q:

A compound is regarded as a pure substance but a mixture is not. Give reasons.

A:
A compound is formed when two or more elements combine chemically. So, compound is a single substance whereas a mixture is obtained when two or more elements or compounds or both are simply mixed in any proportion. Hence, mixtures are not pure.
Q:

(i) Name the living component common to both the complex permanent tissues found in plants. What is its function?
(ii) State any two ways in which these tissues differ functionally from each other.

A:
(i) The living component is known as Parenchyma. Its function is to store food.
(ii) Xylem transports water and minerals and the direction of flow is vertical.
Phloem transports food from leaves to other parts of the plant and the direction of flow is bidirectional.
Q:

List three common objectives of crop improvement.

A:
The common objectives of the crop improvement are as follows:
(i) To improve yield and quality of the crop.

(ii) Development of disease and draught resistance in crop plants.

(iii) Development of crops having shorter duration of maturity so that mutiple rounds of crops can be grown in one year.

Q:

Explain why does a gun recoil when a shot is fired from it?

A:
When a gun is fired, the bullet goes out due to the force applied on it through the trigger(action). The gun recoils backward due to the reaction acting on it in the opposite direction. This gives a backward jerk to the shoulder of the gunman. The change in the momentum of the bullet is equal & opposite to that of the gun.
Q:

A ball of mass 2 kg is kept on a tower of height 30 m. Find its potential energy at this point. If it is allowed to fall freely, find its kinetic energy when it just touches the ground?

A:

m = 2 kg; h = 30 m; g = 10 m/s2

P.E = m × g × h

= 2 kg × 10 m/s2 × 30 m

= 600 J

When ball just touches the ground its kinetic energy, K.E. = (1/2)mv2

v2 - u2 = 2as [Third equation of kinematics]

v2 = 2 × 10 m/s2 × 30 m [As u = 0 m/s]

= 600 m/s

So, K.E. = (1/2) × 2 kg × 600 m/s

= 600 J

The potential energy is completely converted into kinetic energy. This is in accordance to law of conservation of energy.

Q:

Fill in the key words in the given flow chart:

A:
Q:

Sulphur dioxide and nitrogen dioxide gases react with the water vapour present in air. What are the products formed by this reaction? What is this process known as and what are its effects?

A:
Sulphur dioxide and nitrogen dioxide on reaction with water vapours form sulphuric acid and nitric acid respectively. This acid falls down along with the rain and this rain is called Acid rain. It has harmful effects on plants, aquatic animals and infrastructure. Aquatic life dies when water becomes acidic. This acid rain corrodes the metal and stones of buildings and monuments.
Q:

Two objects of masses m1 and m2 exert a force F on each other when they are separated by a distance,r. What happens when
(i) Mass m1 is doubled,
(ii) The distance between them is halved?

A:
The force of gravitation between the two masses will be ,
Q:

(i) A solution has been prepared by dissolving 5 g of urea in 95 g of water. What is the mass percent of urea in the solution ?


(ii)Will blood show Tyndall effect?

A:

(i)



(ii) Blood is a colloidal solution, therefore it will show Tyndall effect.

Q:

Draw a sketch of Bohr’s model of an atom with four shells ?

A:
The sketch for Bohr’s model of an atom with four shells is given as follows :

Q:

Write the formula of :

(i) Ammonium sulphate

(ii) Magnesium nitrate

(iii) Aluminium bromide

A:
(i)

(ii)

(iii)

Q:

a) Draw a diagram of a prokaryotic cell and label the given parts:
i) cell wall ii) nucleoid iii) ribosomes.
b) Complete the given table illustrating the differences between the prokaryotic and eukaryotic cells.

Prokaryotic cell

Eukaryotic cell

Size of the cell small

Size of the cell large

Presence of single chromosome

Membrane bounded organelles present

A:

a)

b)

Prokaryotic cell

Eukaryotic cell

Size of the cell small

Size of the cell large

Presence of single chromosome

More than one chromosome

Absence of membrane bounded organelles

Membrane bounded organelles present

Q:

Who proposed five-kingdom classification? What are the names of kingdoms?

A:

R.H. Whittaker (1969) proposed five-kingdom classification , they are:
i) Monera
ii) Protista
iii) Fungi
iv) Plantae
v) Animalia

Q:

If in an office, 10 tubes of 40 W, 5 fans of 75 W and 2 ACs of 1500 W are used for 8 hours a day. Calculate the energy consumed per day in commercial units of energy.

A:

Power consumed by tubes = p1 = 10 × 40W = 400 W
Power consumed by fans = p2 = 5 × 75W = 375 W
Power consumed by ACs = p3 = 2 × 1500W = 3000 W
Total energy consumption per day, E = p1t + p2t + p3t

or, E = (p1 + p2 + p3)t

= ( 400W + 375W + 3000W ) × 8 h

= 3775 W × 8 h = 30200 Wh

or, E = 30200 Wh/1000 = 30.2 kWh

Q:

An iron piece weighs 600 g in air and 400 g in water. Find volume of the solid.

A:

Given:
Weight of solid in water = 400 g
Weight of solid in air = 600 g
Loss of weight of solid in water = 600– 400g
= 200g
= Mass of water displaced.

Q:

Name A, B, C, D & E in the following diagram.

A:

A - Fusion or melting

B - Vaporization or boiling

C - Condensation

D - Solidification

E - Sublimation

Q:

Give a brief account of the observations made by Rutherford in his alpha particle scattering experiment.

A:

The observations made by the Rutherford is shown by the figure below,

He observed that:

1) Most of the particles passed through the gold foil directly without changing their path, which proved that most of the atom is empty.

2) Slight deflection of some of the particles, and large scale deflection of some particles ,proved that central mass of an atom is very high (called as nucleus) and central mass of an atom is positively charged.

3) Very few -particles (1 in 1 lac) bounced back completely. This shows that nucleus is very small compared to the whole atom.

Q:

Tom was verifying the law of conservation of mass by reacting barium chloride and sodium sulphate.

(i)The colours of barium chloride and sodium sulphate are

(a) blue and white respectively.

(b) blue and blue respectively.

(c) white and white respectively.

(d) white and blue respectively.

(ii)During the experiment, he reacted 209 g of BaCl2 and 145 g of Na2SO4 . If after reaction he obtained 120 g of NaCl, find the amount of BaSO4

he obtained.

A:

(i)

(c) Both the salts are white in colour.

(ii)

Q:

Can law of conservation of mass be verified by heating crystals of ferrous sulphate in a china dish? Give reasons.

A:

When a chemical reaction is carried out in an open container like china dish, some mass will evaporate in the form of vapours or gas. Therefore, the mass taken in the container will no longer remain constant. It means law of conservation cannot be verified by heating crystals of ferrous sulphate in a china dish.

Q:

Name the following:
(a) Tissue that stores fat in our body.
(b) Tissue that connects muscle to bone in animals.
(c) Tissue that forms the animal skin
(d) Tissue that forms the coconut husk.

A:
(a) Adipose tissue
(b) Tendon
(c) Squamous epithelium
(d) Sclerenchyma
Q:

The teacher gave a de-shelled egg to Ritika and an unknown solution in a glass and asked to dip the egg in the solution and observe it after 7 minutes. After 7 minutes the egg was found to be shrunk.

Which of the following inference can be drawn from above observation?

A:

Given solution was hypertonic

Q:

To move a wooden block X of weight 2 kg placed on a horizontal table, John hangs a weight of unknown mass on the other side of the attached string.

(i) The block X suddenly moves rapidly means:

(a) Weight used is less than 2 kg.

(b) Weight used is equal to 2 kg.

(c) Weight used is greater than 2 kg.

(d) Other parameters are required to know the weight.

(ii) Name the law on which a spring balance works.

A:

(i) The correct option is (c).

Explanation: From Newton’s third law of motion, action and reaction are equal and opposite and acts on different bodies. Therefore, the block will move only when the applied force is more than its weight.

(ii) A spring balance works on Newton’s third law of motion.

Q:

(i) Jerry observed using a spring balance that a weight of 5 kg was just enough to slide a block kept on a horizontal surface. The calculated force comes out to be:

(a) 0.98 N

(b) 98 N

(c) 49 N

(d) 0.49 N

(ii) If the weight of the block is doubled, what will be the magnitude of new force?

A:

(i) The correct option is (c).

Explanation: F = mg

= 5 x 9.8 = 49 N

(ii) If the weight of the block is doubled, the new force will also be doubled, i.e., 98 N.

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