AP SSC Class 10 Physical Science Chapter 1 Heat

Heat is a form of energy that is defined as the sum of kinetic energy contained by the molecules of that object. The SI unit of heat is Joules. The AP SSC Class 10 Physical Science Chapter 1 heat discusses the various properties of heat. Heat is directly proportional to the mass of the object and the average kinetic energy. The degree of hotness and coldness of a body is known as temperature. It determines the rate of flow of heat from one body to another. The concept of heat and temperature, although related, are not alike. Let us look at a few differences between them.

Heat Temperature
Heat is the amount of energy that flows in a body Determines the direction of heat flow
Total potential and kinetic energy contained by molecules in an object. The average kinetic energy of molecules in a substance.
Flows from hotter objects to colder objects Rises when heated and lowers when cooled

Thermal Equilibrium Heat And Temperature

  • If two systems, A and B, are in thermal equilibrium individually with another system C, then the systems A and B are in thermal equilibrium with each other.
  • The SI unit of heat is Joule (J) and CGS unit is calorie (cal). The amount of heat required to raise the temperature of 1gram of water by 1°C is called calorie.

1 cal = 4.186 Joules

  • The amount of heat required to raise the temperature of unit mass of the substance by one unit is known as the specific heat. Mathematically, it is represented as follows:

S = Q/mΔt

  • Evaporation is the process of the molecules breaking free from the liquid surface at any given temperature.
  • The process in which the liquid phase changes to a gaseous phase at a constant temperature and constant pressure is known as boiling.

In the next section, let us look at a few chapter questions.

Class 10 Science Chapter 1 Heat Questions

  1. The temperature of an iron rod is 350K. Its temperature in °C is _____.

Solution:

We know that 0°C = 273 K

Temperature in Celsius = Temperature in Kelvin – 273

Substituting the value, we get

= 350 – 273 = 77°C

350 K in Celsius is 77°C

  1. When ice melts, its temperature remains _____.
  2. increases
  3. decreases
  4. remains constant
  5. cannot say

Solution:

The temperature of the ice does not change during melting because the heat energy given to the ice is totally utilized in breaking the bonds between the water molecules.

When ice melts, its temperature remains constant.

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Practise This Question

During a breathing cycle, why do lungs always contain a residual volume of air in it?