Temperature and Thermal properties of materials

Question 1

Define

thermal equilibrium

Answer 1

A condition where two or more objects in contact have the same temperature so that there is no net flow of energy between them.

Energy is transferred from a region of higher temperature to a region of lower temperature until they are in equilibrium.

Question 2

State examples of physical properties that vary with temperature and may be used for the measurement of temperature

Answer 2

• length (liquid-in-glass)
• resistance (thermistor / resistance thermometer)
• potential difference (thermocouple)
• colour (of an electrically heated wire)
• volume of gas (fixed mass at constant pressure)

Question 3

Define

thermodynamic scale

Answer 3

A temperature scale where temperature is measured in kelvin (K), based on the concept of absolute zero.

Absolute zero (0K / -273.15^oC) is the temperature at which a system has zero kinetic energy and therefore minimum internal energy.

Unlike the Celcius and Farneheit scales, this does not depend on the somewhat variable properties of substances (e.g. m.p. and b.p. of water)

Question 4

State an equation used to convert temperatures measured in kelvin to degrees Celsius

Answer 4

T / K = T / °C + 273.15

Question 5

Explain what a thermistor is and how it works

Answer 5

• A resistor whose resistance is dependent on temperature, made of metallic oxides (resistance wire thermometers are made of pure metal such as platinum)
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