7th Class Science Heat Effect of Heat

       Heat

Heat is a form of energy, which is transferred from one body to another of different temperatures.

Heat is measured in degrees and units of heat are Celsius, Fahrenheit and Kelvin. Thermometer is an instrument, which is used for the measurement of heat.

          Effect of Heat

Every object absorbs more or less heat from the atmosphere. A peace of iron heats up quickly, because it absorbs heat fast. Water boils at 100° centigrade. Heat plays an important role in our daily life. Plastic is converted into little solid form of liquid at certain temperature. These properties of plastic are used for the making of various kinds of plastic based products.

Look at the following pictures

     Cold water                                                              Water evaporates  

Cold water evaporates slowly. Evaporation of cold water depends on the temperature of the atmosphere, when external heat is not applied. Water evaporates fast when heat is applied. Rate of evaporation of water will increase if applied heat is increased. Some solid converted into liquid and then gas, when heat is applied. For example ice (solid) converts to water (liquid) and then into water vapor (gas) with the application of heat.

     At what temperature water starts to boil?

(a) 0°C

(b) 10°C

(c) 37°C

(d) 100°C

(e) None of these

Answer: (d)

     The temperature at which a liquid starts to convert into gas is known as:

(a) Melting point

(b) Freezing point

(c) Boiling point

(d) Point

(e) None of these

Answer: (c)