Temperature?is a measure of how hot or cold objects are
Temperature also determines the direction in which thermal energy will flow between two objects (or between an object and its surroundings)
When thermal energy is exchanged, the objects (or systems) involved are said to have a?thermal interaction
The thermal energy exchanged during a thermal interaction is referred to as?heat
During a thermal interaction:
Thermal energy always flows from the hotter object to the colder object
The energy transfer continues until the two objects are in?thermal equilibrium?(i.e. they both have the same temperature)
Thermal energy can be transferred via?conduction,?convection?or?radiation
Temperature is a?scalar?quantity and it is measured using a?thermometer
It is measured in?degrees Celsius?(°C) or?kelvin?(K)
The kelvin is the?SI base unit?for temperature
The temperature of an object is a?macroscopic?measure of the?average kinetic energy?of the particles (atoms or molecules) that make up the object
Absolute temperature
Absolute temperature?is temperature measured in kelvin (K)
Absolute zero?is a temperature of zero kelvin (0 K) and corresponds to the temperature at which the?average?kinetic energy?of the molecules?is at its?minimum
The conversion between the Kelvin and the Celsius scale is given by:
T(K) = T(°C) + 273.15
It is important to notice that?differences in absolute temperatures correspond to differences in Celsius temperatures?
ΔT(K) = ΔT(°C)
Where?ΔT?stands for?temperature change
The?absolute temperature?of a body is?directly proportional to the average kinetic energy of the molecules within the body
The ice point is determined by placing a thermometer in a beaker containing melting ice, while the steam point is determined by placing the thermometer in a beaker with boiling water
Worked Example
Give an estimate of room temperature in kelvin (K).
Step 1: State a reasonable value for room temperature in degree Celsius (°C)
room temperature (°C) ~ 20°C
Step 2: Write down the conversion between Celsius scale and Kelvin scale?
T(K) = T(°C) + 273.15
Step 3: Convert the room temperature value and express it in kelvin (K)
room temperature (K) ~ 293 K
Exam Tip
Remember that the lowest possible temperature on the Kelvin scale is absolute zero (0 K). Therefore, if you are calculating temperature in kelvin and you end up with a negative number, you need to check your work, since negative numbers do not exist on the Kelvin scale.