CHAPTER 4 Heat
4.1 Heat and temperature 4.1.1 Heat (Q in J)
In 3.1 and 3.4 on pages 55 and 56, the concept of energy and heat energy was explained. Heat was defined as: Heat is a form of energy.
It could also be said that heat is the amount of energy contained in a body.
4.1.2 Temperature Temperature refers to how hot or how cold a body is.
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Our sense of temperature, such as touching an object, is unreliable. It is therefore necessary to make use of instruments to obtain accurate and objective measurements.
Definition 4.1 Temperature Temperature is an indication of the degree of hotness or coldness of a body.
4.1.3 Temperature scales Tere are two temperature scales in general use.
4.1.3 (a) Celsius scale (temperature: t)
Anders Celsiusmade a division of 100 units or degrees between the changing phases of pure water, i.e. between the freezing and boiling points.
Zero degrees (0 °C) is the freezing point of pure water at sea level (or themelting point of ice), and 100 degrees (100 °C), higher up the scale, is the boiling point.
4.1.3 (b) Kelvin scale (thermodynamic temperature: T)
This scale also has 100 divisions between the freezing and boiling points of water, but it suggests that if the temperature of a body is reduced to absolute zero, i.e. –273 °C, the body would possess no thermal energy.
Such a condition can however never be attained in practice.
The thermodynamic scale starts at absolute zero (i.e. –273 °C) and rises in divisions, referred to as kelvin (K), equal to that used in the Celsius scale.
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