Heat and Temperature Class 3

BASIC SCIENCE AND ENGINEERING
Heat and temperature class3
Latent heat:(గుప్తో ష్ణం)
the heat required to convert a solid into a liquid or vapour, or a liquid into a vapour, without
change of temperature.
SI unit of latent heat is joule/kg
Any material has two types of Latent heat
Latent heat of Fusion (ద్రవీభవన గుప్తో ష్ణ ం): it is the amount of Heat required to Convert Unit mass
of substance form solid state to Liquid state at its melting point.
It is also the amount of Heat released by a unit mass of liquid when changed into solid at its
freezing point.
Latent heat of vaporization(భాష్పీభవన గుప్తో ష్ణ ం): it is the amount of Heat required to Convert Unit
mass of substance form liquid state to vapour state at its boiling point.
It is also the amount of Heat released by a unit mass of vapour when changed into liquid.
Sublimation(ఉత్ీత్నము): process of conversion of solid directly into vapour.
Sublimation takes place when a boiling point is less than melting point.
Sublimation is shown by camphor or ice in vaccum.
Hoar frost: it is the reverse process of sublimation. i.e., direct conversion of vapour into solid.
Relative Humidity(సాపేక్ష అర్థ్రత్): It is the ratio of amount of water vapour present in a given volume of
atmosphere to the amount of water vapour required to saturate the same volume at same
temperature.
To express the relative Humidity in % then we multiply the ratio with 100.
relative humidity is measured by Hygrometer.
Relative humidity is increases with increase of temperature.
Air conditioning: for Healthy and favorable atmosphere of human being the conditions are as follows:
1. Temperature: from 23degree C to 25 degree C
2. Relative Humidity: from 60% to 65%
3. Speed of air: from 0.75 meter/min to 2.5 meter/min
Thermo dynamics: Thermodynamics is the branch of physics that deals with the relationships between
heat and other forms of energy. In particular, it describes how thermal energy is converted to and from
other forms of energy and how it affects matter.
MCQ:
Which of the following is the fastest process of heat transfer?
a. conduction
b. convection
c. radiation
d. isolation
The factors directly proportional to the amount of heat conducted through a metal rod
are -
a. Time of flow of Heat

b. Area of cross section
c. Temperature gradient
d. All the above
1 gm of ice at 0° C is mixed with 1 gm of steam at 100° C. After thermal equilibrium, the

temperature of the mixture is
a. 0° C
b. 50° C
c. 80° C
d. 100° C
What would be the thermal resistance of an ideal conductor?
a. Zero
b. One
c. Infinity
d. Ten
Why does the bottom of a lake not freeze in severe winter even when the surface is all
frozen?
a. The water has large specific heat

b. The conductivity of ice is low
c. The water has large latent heat of fusion
d. The temperature of the earth at the bottom of the lake is high.
A cooking pot is coated black because -
a. black substances absorb more heat

b. black substances reflect more heat
c. black surfaces are easier to clean
d. the material of the pot would not be damaged
Specific heat is -
a. the specific temperature at which the substance is in solid state.

b. the energy needed to increase the temperature of 1 gram of a substance by 1
degree Celsius.
c. the amount of heat conducted in 1 minute.
d. the heat needed to increase the temperature of 1 gallon of water by 1 degree
Fahrenheit.
How will a metal container full of hot water in vaccum lose heat?
a. by conduction
b. by convection
c. by radiation
d. will stay hot for ever
A block of ice
a. cannot radiate heat

b. can radiate heat but cannot absorb heat
c. can absorb heat but cannot radiate heat
d. can radiate as well as absorb heat
As a solid undergoes a phase change to a liquid state, it
a. releases heat while remaining at a constant temperature.

b. absorbs heat while remaining at a constant temperature.
c. releases heat as the temperature decreases.
d. absorbs heat as the temperature increases.
A cup of hot tea on a metal table in a room loses heat by
a. Conduction
b. Convection
c. Radiation
d. All the above
Which among the following is true of a sphere, a cube and circular plate of same
material and same mass heated to same temperature?
a. Sphere cools the slowest

b. Circular plate cools the fastest
c. Cube cools the fastest
d. Circular plate cools the slowest
At what temperature are the Celsius and Fahrenheit equal?
a. + 40o
b. - 40o
c. - 0o
d. + 100o
What would happen to a hole in a metal sheet when the sheet is heated?
a. It decreases in size
b. It increases in size
c. No change is seen
d. First increases and then decreases
Which of the following is equivalent of a calorie?
a. the specific heat of water.

b. the energy needed to increase the temperature of 1 gram of water 1 degree
Celsius.
c. equivalent to a little over 4 joules of mechanical work.
d. all of the above.
In which of the following processes of heat transfer no medium is required?
a. Conduction
b. Convection
c. Radiation
d. All
In which of the following processes is heat transferred directly from molecule to
molecule?
a. conduction
b. convection
c. radiation
d. all of the above
When a solid, liquid, or a gas changes from one physical state to another, the change
is called
a. melting
b. enthalpy
c. a phase change
d. sublimation
The surface which radiates more heat at a given temperature is
a. Black and Polished

b. White and polished
c. White and Rough
d. Black and Rough
Compared to warm air, cool air can hold
a. more water vapour

b. less water vapour
c. the same amount of water vapour
d. temperature is unimportant here

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BASIC SCIENCE AND ENGINEERING

Heat and temperature class3

Latent heat:(గుప్తో ష్ణం)

SI unit of latent heat is joule/kg

Any material has two types of Latent heat

of substance form solid state to Liquid state at its melting point.

Sublimation(ఉత్ీత్నము): process of conversion of solid directly into vapour.

Sublimation is shown by camphor or ice in vaccum.

Which of the following is the fastest process of heat transfer?

a. Time of flow of Heat

1 gm of ice at 0° C is mixed with 1 gm of steam at 100° C. After thermal equilibrium, the

What would be the thermal resistance of an ideal conductor?

a. The water has large specific heat

A cooking pot is coated black because -

a. black substances absorb more heat

a. the specific temperature at which the substance is in solid state.

a. cannot radiate heat

As a solid undergoes a phase change to a liquid state, it

a. releases heat while remaining at a constant temperature.

a. Sphere cools the slowest

At what temperature are the Celsius and Fahrenheit equal?

Which of the following is equivalent of a calorie?

a. the specific heat of water.

In which of the following processes of heat transfer no medium is required?

The surface which radiates more heat at a given temperature is

a. Black and Polished

Compared to warm air, cool air can hold

a. more water vapour

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