Class 7 Science - Chapter Heat NCERT Solutions | Match the following : (i) Land breeze b

One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be

(a) 80°C    (b) more than 50°C but less than 80°C
(c) 20°C    (d) between 30°C and 50°C

Stainless steel pans are usually provided with copper bottoms. The reason for this could be that

(a) copper bottom makes the pan more durable.
(b) such pans appear colourful.
(c) copper is a better conductor of heat than the stainless steel.
(d) copper is easier to clean than the stainless steel.

Look at Fig. 4.13. Mark where the heat is being transferred by conduction, by convection and by radiation.

An iron ball at 40°C is dropped in a mug containing water at 40°C. The heat will

(a) flow from iron ball to water.
(b) not flow from iron ball to water or from water to iron ball.
(c) flow from water to iron ball.
(d) increase the temperature of both.

A wooden spoon is dipped in a cup of ice cream. Its other end

(a) becomes cold by the process of conduction.
(b) becomes cold by the process of convection.
(c) becomes cold by the process of radiation.
(d) does not become cold.

Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.

In places of hot climate it is advised that the outer walls of houses be painted white. Explain.

Fill in the blanks :
(a) The hotness of an object is determined by its __________.
(b) Temperature of boiling water cannot be measured by a _____________ thermometer.
(c) Temperature is measured in degree ______________.

(d) No medium is required for transfer of heat by the process of __________.
(e) A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of ______________.
(f ) Clothes of ______________ colours absorb heat better than clothes of light colours.

Give two examples each of conductors and insulators of heat.

State similarities and differences between the laboratory thermometer and the clinical thermometer.

State differences between acids and bases.

Classify the changes involved in the following processes as physical or chemical changes:
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f ) Digestion of food

Name the elements that determine the weather of a place.

Fill the missing word in the blank spaces in the following statements:

(a) Wind is——————air.
(b) Winds are generated due to —————— heating on the earth.
(c) Near the earth’s surface __________air rises up whereas ___________ air comes down.
(d) Air moves from a region of ——— pressure to a region of ———.

In addition to the rock particles, the soil contains

(i) air and water
(ii) water and plants
(iii) minerals, organic matter, air and water
(iv) water, air and plants

Why does an athlete breathe faster and deeper than usual after finishing the race?

Match structures given in Column I with functions given in Column II.

Column I                           Column II
(i) Stomata                        (a) Absorption of water
(ii) Xylem                           (b) Transpiration
(iii) Root hairs                    (c) Transport of food
(iv) Phloem                        (d) Transport of water
                                          (e) Synthesis of carbohydrates

Fill in the blanks:

(a) Production of new individuals from the vegetative part of parent is called_____________.
(b) A flower may have either male or female reproductive parts. Such a flower is called_____________.
(c) The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as _____________.
(d) The fusion of male and female gametes is termed as _____________.
(e) Seed dispersal takes place by means of _____________, _____________ and _____________.

Classify the following as motion along a straight line, circular or oscillatory motion:

(i) Motion of your hands while running.
(ii) Motion of a horse pulling a cart on a straight road.
(iii) Motion of a child in a merry-go-round.
(iv) Motion of a child on a see-saw.
(v) Motion of the hammer of an electric bell.
(vi) Motion of a train on a straight bridge.

Why do organisms need to take food?

Fill in the blanks:

(a) An image that cannot be obtained on a screen is called ____________.
(b) Image formed by a convex __________ is always virtual and smaller in size.
(c) An image formed by a __________ mirror is always of the same size as that of the object.
(d) An image which can be obtained on a screen is called a _________ image.
(e) An image formed by a concave ___________ cannot be obtained on a screen.

What will happen if there are no platelets in the blood?

What are stomata? Give two functions of stomata.

Describe the function of the heart.

State the characteristics of the image formed by a plane mirror.

Describe the various ways by which seeds are dispersed.

State whether the following statements are true or false. In case a statement is false, write the corrected statement in your notebook.

(a) Cutting a log of wood into pieces is a chemical change. (True/False)
(b) Formation of manure from leaves is a physical change. (True/False)                                                                                                                                              (c) Iron pipes coated with zinc do not get rusted easily. (True/False)
(d) Iron and rust are the same substances. (True/False)
(e) Condensation of steam is not a chemical change. (True/False)

Describe the different methods of asexual reproduction. Give examples.

The tropical rainforest has a large population of animals. Explain why it is so.

How does the process of fertilisation take place in flowers?