Thermal Energy

Some Facts to Note

1. Any substance is made up of atoms and molecules. The molecules have translational, vibrational and rotational motion.

2. The atoms and molecules are in constant motion. There exist forces of attraction and repulsion between them.

3. Because of motion they possess energy called as the Kinetic Energy (K. E.). Because of the forces the atoms and molecule possess energy called as the Potential Energy (P.E.).

4. The total energy i.e. the sum of K.E. and P.E. possessed by the atoms and molecules is called the thermal energy or the internal energy of the substance.

 

Activity

1. Keep your left hand in hot water and right hand in cold water first and then both the hands in like warm water.

2. Take some hot / boiling water in a bucket and add cold water to it. Similarly take some cold water and add hot / boiling water to it.

 

Experience/ Observations

1. It appears colder to the left hand and hotter to the right hand.

2. The hot / boiling water becomes less hot or warm when cold water is added to it, and the cold water becomes less cold or warmer when hot or boiling water is added to it.

 

Understanding

1. Results obtained by the sense of touch are different from person to person

2. We can only get a rough idea of how hot or how cold an object is by touching it but sense to touch is not accurate or reliable measure of hotness or coldness

3. If an object is very hot or very cold we cannot touch it.

The extent of Hotness or coldness of any substance is accurately measured by a physical quantity called temperature. Temperature is the degree of Hotness or Coldness of a Substance

When a substance is heated, it temperature increases. When it is cooled, its temperature decreases