7 Science Chapter 4 Heat

Chapter Notes and Summary
• A reliable measure of hotness of an object is its temperature.
• Temperature is measured by a device called thermometer.
• Clinical thermometer is used for measuring our body temperature.
• A clinical thermometer reads our temperature from 35°C to 42°C.
• normal temperature of a human body is 37°C.
• In order to measure temperature of other objects, we make use of Laboratory thermometer.
• range of laboratory thermometer is from– 10°C to 110°C.
• heat flows from a body at a higher temperature to a body lower temperature. Heat can flow from one object to another in three different ways, namely, conduction, convection and radiation.
• In solids, generally, heat is transferred by conduction. In liquids and gases, heat is transferred by convection. No medium is required for transfer of heat by radiation.
• Heat always flows from hotter objects to colder objects.
• materials which allow heat to easily pass through them are conductors of heat.
• materials which do not allow heat to pass through them easily are called insulators of heat.
• When heat falls on same object, then some part of heat gets reflected, some portion gets absorbed and some part gets transmitted.
• Dark coloured objects absorb radiation better than light coloured objects. That is reason, we feel more comfortable in light coloured clothes during summer.
• Woollen clothes keep us warm during winter. It is because wool is a poor conductor of heat and it has air trapped in between fibres.

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