Temperature

Question 1

Thermal energy flows from a region of __________ to a region of ___________ .

Answer 1

Thermal energy flows from a region of higher temperature to a region of lower temperature.

Question 2

What is meant by thermal equilibrium?

Answer 2

Two objects, in contact with each other, are in thermal equilibrium if they are at the same temperature and there is no net transfer of thermal energy between the objects.

Question 3

There are some physical properties that vary with temperature, and can be used to measure temperature. List 4 of these physical properties and the corresponding thermometers.

Answer 3

• length of a column of liquid in a glass tube (liquid-in-glass thermometers)
• resistance of a metal wire (resistance thermometers)
• resistance of a thermistor
• e.m.f. produced by a thermocouple
• pressure of a fixed volume of gas (constant-volume gas thermometers

Question 4

Using a different thermometric substance and thermometric property would lead to a different temperature scale. Agreement between scales occurs only at the two fixed points. Why?

Answer 4

When a temperature scale is calibrated, it is assumed that the thermometric property changes linearly with temperature.
However, the property may not vary linearly with temperature.

Question 5

State what is meant by the absolute zero of temperature.

Answer 5

The temperature at which atoms have minimum internal energy.

Question 6

State what is meant by internal energy.

Answer 6

The sum of the random distribution of kinetic energy and potential energy of atoms.

Question 7

The equation linking temperature on the Celsius scale and thermodynamic temperature is

Answer 7

T / K = T / °C + 273.15

Question 8

Why is the thermodynamic scale of temperature an absolute scale?

Answer 8

Because it does not depend on the property of any substance.

Question 9

What are the fixed points on the thermodynamic scale of temperature?

Answer 9

(1) Absolute zero – the temperature at which atoms have minimum internal energy, which is defined as 0 K (equal to -273.15 °C).
(2) The triple point of water – the temperature at which ice, water and water vapour can co-exist, which is defined as 273.16 K (equal to 0.01 °C).

Question 10

What are the advantages and disadvantages of a thermocouple thermometer?

Answer 10

Advantages:

(1) Fast response time because it has a small thermal capacity.
(2) Test junction is physically small - it can measure temperature of very small objects or at a point on a larger object.
(3) Can be used to measure temperature difference.
(4) Wide temperature range: from -200 to 2600 degree Celcius.

Disadvantage:
(1) Non-linear, so it requires calibration.