Physics

Chapter - 6: Effect of Heat on Matter

👉 All Chapter Contents 👈 

• 6.1  Heat and Temperature

• 6.2  Thermometric Properties of matter

• 6.3  Thermal Expansion of Matter

• 6.4  Effect of Temperature on Change of State

• 6.5  Specific Heat

• 6.6  Fundamental Principles of Calorimetry

• 6.7  Effect of Pressure on Melting Point and Boiling Point

What is thermometric properties of matter?

Special properties of matter are used to measure the temperature. Some physical properties of substance change uniformly with the change of temperature. Using that physical property of substance temperature can be measured easily accurately and it is called the thermometric property of that substance.

What are the thermometric properties of substances?

The thermometric properties of substances are - Volume, Resistance, Pressure, etc.

What are the two processes of vaporization?

The two processes of vaporization are - i) Evaporation and ii) Boiling.

What is the unit of heat capacity?

The unit of heat capacity is JK-1.

What is the is the unit of specific heat?

The unit of specific heat is Jkg-1K-1.

What is melting point?

At standard pressure and at the temperature at which pure ice melts to water and temperature remains same until the melting is complete is called melting point.

What is expansion?

Due to increase of temperature average equilibrium of each molecule of every substance gets displaced towards the exterior and body expands. With the application of heat the length, area and volume of solid substance expand, the volume of liquids increases and the volume and pressure of gas increase. This is called expansion.

What is 1 degree celsius?

At normal pressure the temperature difference between melting ice and boiling water is 1 of 100 is 1 degree celsius.

What is anomalous expansion of water?

Most of the liquids expand in volume when heated and contract when cooled. But water is an exception. In 4*C, whether heat is applied or extracted it does not expand. This is called the anomalous of water.

What is boiling?

The process in which a liquid is rapidly converted into vapour by increasing its temperature through application of heat is called boiling.

What is the temperature of triple point of water?

The temperature of triple point of water is 273 K.

What is meant by heat capacity of a body is 10 JK-1?

The heat capacity of a body is 10 JK-1 means 10 J heat is required to raise the temperature of the body through 1 K.

What is meant by the specific heat of lead is 130 Jkg-1K-1?

The specific heat of lead is 130 Jkg-1K-1 means 130 J heat is required to raise the temperature of 1 kg of lead through 1 K.

Do you think the two bodies with equal heat can have different temperature? - Explain it.

If two water vessels with equal mass are heated for same amount of time the vessel with greater mass will have more temperature. Again if a iron bar and a brass bar are heated with same amount of heat, iron bar will receive heat from brass bar and brass bar will reject heat. That means although heat is equal the temperature can be different.

Why do two pieces of ice pressed together get attached or joined together?

As the pressure acts on the surface of contact of the two pieces of ice, the melting point goes down i.e the melting point becomes less than 0*C. But the temperature of the surface of contact melts. The required amount of heat needed for melting is collected from the ice. After the removal of pressure the melting point again becomes 0*C. As a result the water obtained from the fusion of ice at the surface of contact again freezes to ice. For this reason if pressure is applied then two pieces of ice untie together to form a single piece.

Express -273*C temperature in Kelvin scale.

We know from the relation between Celsius and Kelvin scales.

1*C difference in temperature = 1 K difference in temperature.

But the Kelvin scale reading can be obtained by adding 273 to Celsius scale reading.

So, 0*C = 273 K

1*C = (1+273) K

-273*C = (-273 + 273) K

= 0 K

-273*C in Kelvin scale is 0 K.

Most of the substances expand when heat is applied, but there is a difference. What is this?

Most of the substances expand when heat is applied. But there is an exception to the general law. For example- water. When heat is applied to 0*C temperature of water its volume does not expand but contract. This anomalous expansion is apparent till 4*C temperature of water.

Explain the fundamental principle of Calorimetry.

When two bodies of different temperatures are brought in thermal contact then reception and donation of heat take place. The body at higher temperature leaves heat. This give and take will continue until they reach at the thermal equilibrium. 

If no heat is lost during donation and reception of heat, then the amount of heat given up by the body at higher temperature will be equal to the heat gained by the body at lower temperature.

So, Heat lost = Heat gained

It is called the principle of Calorimetry.

Prove, Heat capacity = mass x specific heat.

We know, the amount of heat required to increase the temperature of a body through 1 K is called its heat capacity. Again if the specific heat on the material of a body is S, the S joule heat is required to raise the temperature of the body through 1 K.

To increase the temperature through 1 K of a body with a mass of m kg the amount of heat required = m S joule.

It is the heat capacity of the body with a mass of m kg.

Heat capacity, C = m S joule

Heat capacity = mass x specific heat.

What is meant by the specific heat of copper is 400 Jkg-1K-1?

The specific heat of copper is 400 Jkg-1K-1 means 400 J heat is required to raise the temperature of 1 kg of copper through 1 K. Again the heat capacity of 1 kg of copper is 400 JK-1.

Explain the fundamental principle of Calorimetry in the temperature change of alloy.

When two bodies of different temperatures are brought in thermal contact and if no heat is lost during donation and reception of heat, then the amount of heat given up by the body at higher temperature will be equal to the heat gained by the body at lowest temperature.

So, Heat lost = Heat gained.

That is, heat lost by alloy = heat gained by calorimetry and water.

So, it can be assumed that no heat will go outside of the calorimeter and no heat will enter into it. 

So in total heat resistant state two different bodies with different temperatures exchange heat.

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Question Bank

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6.1 Heat and Temperature

• What is physics?