Question

(b) Name four effects which the heat energy can
bring about in a material body.​

Answer 1

Answer:

Heat is a form of energy. It flows from a body at a higher temperature to a body at a lower temperature. Temperature is a measure of the degree of hotness or coldness of a substance. Heat gets tranferred by the processes of coduction, convection and radiation.

Effects of Heat Energy

Heat energy produces many effects in materials and in living organisms. The effects of heat energy are the following:

(i) When heat is supplied to a body its temperature rises: When a material body, solid, liquid or gas, is given heat energy, its temperature increases. When this hot body gives out heat energy its temperature decreases.

(ii) Heat energy may bring about chemical changes in a substance: When we heat substances, the heat energy breaks the original bonds between the elements and new products with new bonds are formed. For example, if marble (calcium carbonate) is heated, it turns into calcium oxide and carbon dioxide.

(iii) A body may catch fire if it is sufficiently heated and if it is flammable. The burning of substances in air or oxygen on heating, with the release of large amount of heat energy and light energy is called combustion. Substances that burn easily in air are called flammable or combustible substances, e.g., wood, coal, petrol, etc. Substances that do not burn easily in air are called incombustible substances, e.g., glass, stone, metals, etc.

(iv) On heating, change of state may occur, i.e. a solid may change into a liquid and a liquid may change into a gas. For example if ice (solid) is heated it changes its state to water (liquid) and if this water is further heated it becomes water vapour (gas). Conversely when a gas loses heat energy it changes into a liquid and on further cooling it freezes into a solid.

Answer 2

Answer:

Heat energy produces a number of effects in material as well as living bodies.These effects are listed below:

1. Heat energy brings about a change in temperature.
2. Heat energy brings about a change in dimensions.
3. Heat energy brings about a change in state.
4. Heat energy brings about a chemical change.