Temperature Flashcards
S.I. unit for temperature
K (Kelvin)
Relationship between ºC and K
__ K = __ ºC + 273
What is the difference between heat energy and temperature?
Temperature indicates the heat energy level of a body whereas heat energy refers to the internal energy of a body
What instruments are used to measure temperature? (3)
Liquid in glass thermometers
Digital thermometers
Laboratory thermometers
Examples of liquid in glass thermometers (4)
Clinical thermometer
Laboratory thermometer
Mercury in glass thermometer
Alcohol in glass thermometer
What are the liquids mercury and alcohol called?
Thermometric liquids
2 properties used for measurement of temperature
Volume and Voltage
Which thermometer uses voltage to measure temperature?
Thermocouple thermometer
What makes a physical property suitable for measurement of temperature?
The change in the physical property must be proportional to changes in temperature so that the scale is linear
Define ice point
The temperature of pure melting ice at standard atmospheric pressure. 0ºC
Define steam point
The temperature of pure boiling water at standard atmospheric pressure. 100ºC
How are fixed points used when calibrating a thermometer?
1) Place the thermometer in ice and mark its level (0ºC)
2) Place the thermometer in boiling water and mark its level (100ºC)
3) The distance between the two marks is divided into 100 equal sections
What is the temperature of a healthy human?
37.5ºC
3 differences between laboratory and clinical thermometer?
Clinical thermometer:
1) Short range (35ºC - 42ºC)
2) Presence of constriction
3) Used to measure temperatures of patients
Laboratory thermometer:
1) Long range ( -10ºC - 110ºC)
2) No constriction
3) Used to measure temperature of air and solutions
What is the purpose of the constriction in a clinical thermometer?
It prevents back flow of mercury/alcohol when it is removed from the patients mouth
5 differences between mercury and alcohol thermometer
Mercury:
1) Costly
2) Poisonous
3) Less visible
4) Does not stick to glass
5) Accurate
Alcohol:
1) Cheap
2) Not poisonous
3) More visible
4) Sticks to glass
5) Not as accurate
What does the sensitivity of a thermometer refer to?
The change in volume or height of the thermometric liquid for each degree change in temperature
When is a thermometer sensitive?
When the height of the thermometric liquid thread changes by a larger amount per degree change in temperature
Factors affecting the sensitivity of a thermometer (3)
1) The expansion/contraction of the thermometric liquid when there is a change of temperature
2) The diameter of the capillary tube
3) The volume of the thermometric liquid in the bulb of the thermometer
Does alcohol or mercury expand more? By how much?
Alcohol expands four times more than mercury for the same rise in temperature
What will a smaller diameter of the capillary tube do to the sensitivity of a thermometer?
The thermometer will be more sensitive as it allows the thermometric liquid to move a longer way through the capillary tube for a small change in temperature
What will a greater volume of the thermometric liquid do to the sensitivity of the thermometer?
The thermometer will be more sensitive
What does the range of a thermometer indicate?
It gives an indication of the minimum and maximum temperature it can measure
What is the linearity of a thermometer?
It is the volume of or height of the thermometric liquid in the capillary tube varies uniformly with temperature
When does a thermometer have a linear scale?
If the height of the alcohol thread in the capillary tube changes by equal number of divisions with equal change in temperature
How does a thermocouple thermometer work?
It measures temperature through the potential difference between bodies having a difference in their temperature
Advantages of using a thermocouple thermometer (3)
1) It can measure rapid varying temperature
2) It has a large temperature range
3) It can measure temperature at a point
