Thermal Properties

Question 1

What is the kinetic model?

Answer 1

Gases, liquids, and solids are made up of atoms, molecules, and/or ions, with differing behaviors across the three phases.

Question 2

Describe the arrangement of particles in gases.

Answer 2

Particles are well separated with no regular arrangement.

Question 3

Describe the arrangement of particles in liquids.

Answer 3

Particles are close together with no regular arrangement.

Question 4

Describe the arrangement of particles in solids.

Answer 4

Particles are tightly packed, usually in a regular pattern.

Question 5

How do particles in gases move?

Answer 5

They vibrate and move freely at high speeds.

Question 6

How do particles in liquids move?

Answer 6

They vibrate, move about, and slide past each other.

Question 7

How do particles in solids move?

Answer 7

They vibrate but generally do not move from place to place.

Question 8

What are the two types of energy present in particles?

Answer 8

Kinetic energy and potential energy.

Question 9

What determines the temperature of a body?

Answer 9

Kinetic energy.

Question 10

What determines the state of a body?

Answer 10

Potential energy.

Question 11

List the four states of matter.

Answer 11

• Solid
• Liquid
• Gas
• Plasma

Question 12

What happens to energy during a change of state?

Answer 12

Energy is either taken in or given out.

Question 13

What is latent heat?

Answer 13

Energy absorbed during a change of state that does not produce a change in temperature.

Question 14

What is the latent heat of vaporization compared to the latent heat of fusion?

Answer 14

Latent heat of vaporization is higher than the latent heat of fusion for the same substance.

Question 15

How does evaporation differ from boiling?

Answer 15

Evaporation occurs over a wide range of temperatures, while boiling occurs at a single temperature.

Question 16

What factors affect evaporation?

Answer 16

• Surface area
• Wind
• Pressure

Question 17

Define boiling point.

Answer 17

The temperature at which saturated vapor pressure equals external atmospheric pressure.

Question 18

What is specific heat capacity?

Answer 18

The heat energy required to increase the temperature of 1 kg of a substance by 1 °C or 1 K.

Question 19

What is the unit of specific heat capacity?

Answer 19

J kg-1 K-1 or J kg-1 °C-1.

Question 20

What is heat capacity?

Answer 20

The heat energy required to increase an object’s temperature by 1 °C or 1 K.

Question 21

What is the unit of heat capacity?

Answer 21

J K-1 or J °C-1.

Question 22

What is the principle behind measuring specific heat capacity?

Answer 22

Supply a known amount of energy to a known mass of material and measure the rise in temperature.

Question 23

What is the specific latent heat of fusion?

Answer 23

The energy required to change the state of 1 kg of material from solid to liquid without a change of temperature.

Question 24

What is the specific latent heat of vaporization?

Answer 24

The energy required to change the state of 1 kg of material from liquid to vapor without a change of temperature.

Question 25

What is the specific latent heat of vaporization of water?

Answer 25

Approximately 2.3 x 10^6 J kg-1.

Question 26

What is the specific latent heat of fusion of ice?

Answer 26

Approximately 3.3 x 10^5 J kg-1.

Question 27

What is the First Law of Thermodynamics?

Answer 27

The internal energy of a system depends only on its state; the increase in internal energy equals the sum of the energy supplied by heating and the work done on the system.

Question 28

What does the internal energy of a gas depend on?

Answer 28

The state of the system and the sum of the random distribution of kinetic and potential energies associated with its molecules.

Question 29

How can the internal energy of a gas be increased?

Answer 29

* Heating the body * Doing work on the body

Question 30

Write the equation for the First Law of Thermodynamics.

Answer 30

ΔU = ΔQ + ΔW.

Question 31

What happens to temperature when work is done on a gas?

Answer 31

The gas becomes hotter.

Question 32

If 100 J of energy is added to a system that does no external work, what is the increase in internal energy?

Answer 32

ΔU = 100 J.

Question 33

If 100 J of energy is added to a system that does 40 J of external work, what is the increase in internal energy?

Answer 33

ΔU = 60 J.

Question 34

What is the work done against the atmosphere when a gas expands?

Answer 34

p ΔV.

Question 35

What is the significance of the continuous-flow calorimeter?

Answer 35

It measures specific heat capacity without needing to know the thermal capacity of the apparatus.

Question 36

What is the gain in potential energy of a molecule?

Answer 36

6.3 x 10-20 J molecule-1 ## Footnote Calculated using the formula: (18 x 10-3 kg x 2.1 x 106 J) / 6.x 10 23

Question 37

What does the area under a pressure-volume graph represent?

Answer 37

The work done on or by a gas ## Footnote This is also referred to as an indicator diagram.

Question 38

What is an isothermal change?

Answer 38

A change from P to Q where the gas expands at constant temperature ## Footnote Boyle’s law applies.

Question 39

What happens to ΔU during an isothermal change?

Answer 39

ΔU = 0 ## Footnote There is no change in temperature.

Question 40

What is the sign of ΔW during an isothermal expansion?

Answer 40

ΔW is negative ## Footnote Work is done by the gas as it expands.

Question 41

What happens to ΔQ during an isothermal change?

Answer 41

ΔQ is positive ## Footnote Equal to the work done by the gas.

Question 42

What is an isobaric change?

Answer 42

A change from Q to R when the gas is cooled at constant pressure ## Footnote Charles’ law applies.

Question 43

What happens to ΔU during an isobaric change?

Answer 43

ΔU is negative ## Footnote The temperature is decreasing.

Question 44

What is the sign of ΔW during an isobaric change?

Answer 44

ΔW is positive ## Footnote Work is done on the gas as it contracts.

Question 45

What happens to ΔQ during an isobaric change?

Answer 45

ΔQ is positive ## Footnote Heat is removed from the gas to keep pressure constant.

Question 46

What is an isovolumetric change?

Answer 46

A change from R to P where the gas is warmed at constant volume ## Footnote The pressure increases.

Question 47

What happens to ΔW during an isovolumetric change?

Answer 47

ΔW is zero ## Footnote There is no change in volume.

Question 48

What happens to ΔQ during an isovolumetric change?

Answer 48

ΔQ is positive ## Footnote Heat goes into the system to raise the pressure.

Question 49

What happens to ΔU during an isovolumetric change?

Answer 49

ΔU is positive ## Footnote Equal to the heat going in.

Question 50

What is an adiabatic change?

Answer 50

An expansion or contraction in which no heat enters or leaves the gas ## Footnote ΔQ is zero.

Question 51

What happens to ΔW during an adiabatic expansion?

Answer 51

ΔW is negative ## Footnote Work is done by the gas as it expands.

Question 52

What happens to ΔU during an adiabatic expansion?

Answer 52

ΔU is negative ## Footnote The internal energy is decreasing.