Friday, 4 June 2021

Class 7 Science: Chapter Heat - Important Points To Remember (#class7Science)(#cbse2021)(#eduvictors)

 Class 7 Science: Chapter Heat - Important Points To Remember

Class 7 Science: Chapter Heat - Important Points To Remember (#class7Science)(#cbse2021)(#eduvictors)

Heat is a form of energy. We use this energy to generate electricity, among other things.

The hotness or coldness of a body is relative.

The temperature of a body is a measure of the degree of hotness of the body. We measure it by comparing it with a universal standard.

The Celsius and Fahrenheit scales are commonly used to measure temperature. Ice melts at 0°C or 32°F. and water boils at 100°C or 212°F.

Heat causes a rise in temperature. It also causes expansion and change in the state of matter.

Heat flows or travels in three ways – conduction, convection and radiation.

Conduction is the process by which heat flows through a substance without the movement of the substance itself.

Convection is the process of transfer of heat in a liquid or gas by the movement of the liquid or gas.

Radiation s the process by which heat travels without the help of a material medium. Radiant heat travels in straight lines, in all direction from a hot body.

Everybody emits (gives out) radiant heat. The emission of radiant heat from a body depends upon its temperature and colour.

When radiant heat falls on a body, a part of it is absorbed and the rest is reflected. How much radiant heat a body absorbs and how much it reflects depend on its colour and the nature of its surface. Shiny white bodies are the best reflectors, while rough black bodies are the best absorbers of radiant heat. Black bodies absorb and emit radiant heat the best.

Evaporation takes place due to vapour formed at the surface of the liquid. Boiling takes place due to vapour through the liquid inside it.

The air gets trapped between two layers of warm clothes. This layer prevents our body heat to escape from the surroundings. More layers of thin clothes will allow more air to get trapped and as a result, we will not feel cold. So wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing.

In places of hot climate it is advised that the outer walls of houses be painted white because light colour reflects most of the heat that falls on it, and therefore, the temperature inside the house is reduced.

This thermometer is used in homes. It is basically used to measure the temperature of humans. A clinical thermometer has a temperature range of only 35°C to 42°C

⑯ A laboratory thermometer has a temperature range of -10°C to 110°C.

Mercury is a very toxic substance. Hence, nowadays digital thermometers have become more popular, which do not contain mercury.

👉See Also:

Ch 4 Heat (Q & A)
Ch 4 Heat (MCQs) 
Ch 4 Heat (Worksheet)

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