Question

1)Give two important effects of heat ?

2)a special kind of glass is used as ovenware for baking.what property should such glass have prevent it from breaking

?

Answer 1

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.

Ovenware Glass


It is made of pyrex glass. It has special properties that it does not expand on heating which give it a non-breakable property. Such glasses possess a large value of breaking point to prevent it from breaking under high temperatures