10th Class Physics - Question & Answers

10th Class Physical Science - Question Bank

Define frost. When do frost form?

Frost : Frost is a solid deposition of water

vapour from humid air. It is formed when

temperature of a solid surface is below the

freezing point of water and also below the

frost point.

What is rain?

Rain : Rain is liquid water in the form of

droplets that have condensed from

atmospheric water vapour.

Define deposition.

Deposition : The process in which a

gaseous phase changes to solid phase

directly with out passing through an

intermediate liquid phase is called

deposition. It is known as resublimation.

Define latent heat.

Latent heat : The quantity of heat energy

required to change unit mass of substance

from a lower state to higher state, without

rising in temperature is called Latent heat.

10th Class Physics - Question & Answers - heat

10th Class Physical Science - Question Bank

How do you appreciate the role of the
higher specific heat of water in
stabilizing atmospheric temperature
during winter and summer seasons?

The sun delivers a large amount of

energy to the earth daily. The water

sources on earth, particularly the oceans,

absorb energy for maintaining a relatively

constant temperature. They can absorb

large amounts of heat at the equator

without rise in temperature due to high

specific heat of water. Therefore oceans

moderate the surrounding temperature

near the equator.

Also ocean water transports the heat

away from the equator to the polar

regions. This transportation helps in

moderate the temperature or climates in

the areas that are far from the equator.

The water in oceans can stabilize the

temperatures on earth in winter and

summer seasons.

What role does specific heat play in
keeping a watermelon cool for a long
time after removing it from a fridge on
a hot day?

If specific heat is high, the rate of rise or

fall in temperature is low. So watermelon

takes long time to rise in its temperature.

Hence Watermelon brought out from a

fridge retains its coolness for a long time

than other fruits. Because the watermelon

consists of more water and water has

greater specific heat value.

If you are chilly outside the shower
stall, why do you feel warm after the
bath if you stay in the bathroom?

After bath, the number of vapour

molecules per unit volume in the bath

room is greater than the number of vapour

molecules per unit volume outside the

bath room. When we try to dry ourselves

with towel, the vapour molecules

surrounding us condenses on our body.

Hence we feel chilly (warm) after bath as

condensation is a warming process.

10th Class Physics - Question & Answers - Heat

10th Class Physical Science - Question Bank

Equal amounts of water are kept in a
cup and in a dish. Which will evaporate
faster? Why?

The rate of evaporation increases with

increasing in surface area. The surface

area of water in dish is more than the

surface area of water in cup. So Water in

dish will evaporate quickly

Suggest an experiment to prove that
the rate of evaporation of a liquid
depends on its surface area and
vapour already present in surrounding
area.

Experiment to prove that Evaporation

depends upon the surface area of the

liquid:

Take 5ml of spirit in a small plate And take

5ml of spirit in another big plate (without

lid). Keep them some time.

Observation : The spirit in the big dish

that disappears quickly, where we find

some spirit in the other dish which is

small. This means that Evaporation

depends upon the surface area of the

liquid. If surface area increases the rate of

evaporation also increases.

Experiment to prove that Evaporation

depends upon the vapour already present

in surrounding area:

Take 5ml of spirit in two small cups. Put

one cup in the A.C. room and put another

in the normal room. Measure the time

taken for disappear the spirit from the

cups.

Observation: The spirit in the normal

room disappears quickly.This means that

the rate of evaporation depends upon the

vapour already present in surrounding

area. If the vapour in atmosphere

increases then the rate of evaporation

decreases.

10th Class Physics - Question & Answers - Heat

10th Class Physical Science - Question Bank

Your friend is asked to differentiate between evaporation and boiling. What questions could you ask to make him to know the differences between evaporation and boiling?

I would like to ask the following questions:

* Does boiling of a substance takes place

at any temperature?

* Does evaporation at any temperature or

not?

* Is evaporation a surface phenomenon or

bulk phenomenon?

* At which temperature does water boils?

* The water in wet clothes dries due to

wind. Is wind provides 100oC ?

What happens to the water when wet
clothes dry?

When wet clothes kept in open place, due

to large area exposed to air, the water

molecules absorb heat from surroundings

and change its state by leaving the

clothes dry on wind blows. This process

is evaporation.

10th Class Physics - Question & Answers

10th Class Physical Science - Question Bank

Why do we get dew on the surface of a cold soft drink bottle kept in open air?

The temperature of the cold soft drink bottle is less than the temperature of atmosphere. The water molecules present in air touches the surface of the bottle and lose their kinetic energy. As a result the temperature of water molecules decrease and condenses on the surface of the bottle. These water droplets are seen as dew.

Write the differences between evaporation and boiling.

Evaporation : The process of escaping of molecules from the surface of a liquid at any temperature is called evaporation. Evaporation is a cooling process. It is a surface phenomenon. Boiling : The process in which the liquid phase changes to gaseous phase at a constant temperature and pressure is called boiling. Boiling does not cause cooling. Boiling is a bulk phenomenon.

Does the surrounding air become warm or cool when vapour phase of H2O condenses? Explain.

Condensation is a warming process. The process of phase change of vapour to liquid is condensation. When vapour touches a cool object the molecules in vapour lose kinetic energy.

As a result the temperature of water molecules decreases and condenses on the surface of the cool object. This is an exothermic reaction. So the average kinetic energy of the molecules in vapour

increases. Thus the surrounding temperature increase.

Digital teaching - e-learning: How optical fiber works?

Digital Class room - e-learning: How optical fiber works?

An optical fiber cable containing one or more optical fibers that are used to carry light. The optical fiber works on the principle of Total internal Reflection. It helps us in so many industries, data transferring, Medical Surgeries and many more. Here is a wonderful video which helps you to understand about "how the optical fiber works" in your digital class room or e-learning platform.

Digital teaching - e-learning: Mirages

Digital Class room - e-learning: Mirages

Mirage is an optical illusion caused by atmospheric conditions, especially the appearance of a sheet of water in a desert or on a hot road caused by the Total internal reflection of light. Here you can view a wonderful video which helps you to understand about formation of mirages in your digital class room or e-learning platform.