Chapter 2A: Energy, Temperature & Heat

Question 1

What is work?

Answer 1

Mechanical work is done when a force pushes, pulls or lifts matter.

Question 2

What is internal energy?

Answer 2

Internal energy is the collective microscopic kinetic and potential energy of the molecules in a substance; it is a fundamental thermodynamic quantity.

Question 3

What is radiant energy?

Answer 3

• Radiant energy is the energy associated with electromagnetic waves (photons).
• It is emitted by all bodies at temperatures above 0 K.
• RE = hc / λ

Question 4

Define temperature

Answer 4

Temperature is a measure of the average kinetic energy of the atoms and molecules within a substance.

Question 5

What happens at 0°C?

Answer 5

Water/ice melts

Question 6

What happens at 100°C

Answer 6

Water boils (at sea level)

Question 7

What is the absolute 0?

Answer 7

0 K is the absolute zero temperature. At this temperature, atomic motion (vibrations, rotations) are at a minimum (=no motion)

Question 8

What is heat?

Answer 8

Heat is a form of energy in the process of being transferred from one object to another because of a difference in temperature.
(There is a transfer of heat until both objects have the same temperature)

Question 9

What is the first law of thermodynamics?

Answer 9

1. Heat is a form of energy

2. Energy is conserved

Question 10

Statement of conservation of energy:
ΔQ= ΔU+ΔW
What are the variables?

Answer 10

ΔQ= the amount of heat added to a system (J)
ΔU= change in internal energy 
ΔW= work done by the system on its surroundings

Question 11

What is heat capacity?

Answer 11

Heat capacity is the ratio of the heat added to a substance to its corresponding rise in temperature.

Question 12

What is specific heat capacity?

Answer 12

Specific heat capacity is the amount of heat (energy) required to raise the temperature of 1kg by 1°C.

Question 13

Which is greater: specific heat capacity at constant pressure or specific heat capacity at constant volume?

Answer 13

Specific heat at constant PRESSURE is always greater than specific heat at constant volume. (cp=cv +R’)

Question 14

Which has a higher specific heat capacity: water or air?

Answer 14

Water has a higher heat capacity. About 4x higher.
Water = 4186 J/kgK
Dry air = 1005 J/kgK (at constant pressure)

Question 15

What does it mean that water has a higher specific heat capacity than air?

Answer 15

It means that water takes longer to heat up and longer to cool down.
→ Oceans take longer to heat up in the summer but are also slower to cool down in the winter (compared to heating/cooling of air)

Question 16

What is sensible heat?

Answer 16

Sensible heat is the heat exchanged in a process associates with a change in temperature of the object.
→Formula: Qsens = CΔTm (C=specific heat capacity, either cp or cv depending on the process ; m=mass)

Question 17

What is latent heat?

Answer 17

Latent heat is the energy required for a phase transition of a substance at constant temperature and volume.
QL= L*m where L is the latent heat of a specific phase transition

Question 18

What is the phase change from solid to liquid?

Answer 18

Melting/Fusion

Question 19

What is the phase change from liquid to solid?

Answer 19

Freezing

Question 20

What is the phase change from liquid to vapour?

Answer 20

Evaporation/vaporization

Question 21

What is the phase change from vapour to liquid?

Answer 21

Condensation

Question 22

What is the phase change from solid to vapour?

Answer 22

Sublimation

Question 23

What is the phase change from vapour to ice?

Answer 23

Deposition

Question 24

Why is the release of heat due to the condensation of (liquid) water and the freezing of ice important to the atmosphere? (3)

Answer 24

• It drives cumulus cloud convection (release of energy in the cloud.
• It intensifies mid-latitude cyclones and hurricanes.
• It is an important driver for the global circulation (transport of water vapour followed by release of latent heat at different locations in the atmosphere)

Question 25

Why are water evaporation and evaporation from clouds/precipitation important to the atmosphere? (2)

Answer 25

• It cools the air

- It supplies moisture to the air (increasing humidity)