8. Thermal Processes

Question 1

Explain thermal equilibrium

Answer 1

It describes a state in which two or more objects have the same temperature and that there is no net transfer of energy between them

Question 2

Explain Conduction

Answer 2

It is a process of energy transfer where energy is transferred through the passing on of vibrational motion from particle to particle

Question 3

Which is the better conductor of thermal energy?

Answer 3

Metals are generally better conductors of thermal energy

Question 4

Why are metals generally better conductors of thermal energy?

Answer 4

1. As they have free moving electrons
2. They are smaller in size and higher in speed hence allowing them to move easily and transfer heat faster

Question 5

Why is transfer of heat less effective in liquid and gas then solid?

Answer 5

1. As the particles in liquid and gas is spaced further apart hence not allowing them to transfer the thermal energy as efficient as solid does.

Question 6

Explain Convection

Answer 6

It is a process of energy transferred by means of convection currents of a fluid (liquid or gas), due to difference in density

Question 7

How does the convection current happens?

Answer 7

1. The liquid at the bottom of the pot expands due to heat
2. The warmer and less dense liquid starts rising upwards while the cooler and denser liquid sinks down
3. This process repeats continuously, forming a convection current

Question 8

Explain Radiation

Answer 8

It is a process of energy transfer by electromagnetic waves. It does not require a medium

Question 9

What are the factors affecting rate of radiation?

Answer 9

1. Surface Temperature
2. Surface Area
3. Surface color and texture

Question 10

How does Surface Temperature affect the rate of radiation?

Answer 10

• When surface temperature is higher, rate of temperature decrease is higher because higher amount of radiation is being emitted

Question 11

How does Surface Area affect the rate of radiation?

Answer 11

• Greater surface area leads to higher rate of radiation emitted

Question 12

How does Surface Color and Texture affect the rate of radiation?

Answer 12

• The more matt, rough, and dark-colored the surface is, the higher the rate of radiation

Question 13

What are some applications of conduction?

Answer 13

1. Hair Dryers: Energy is transferred from heating element to fast-flowing air
2. Instant water heaters: Cold water is passed through heating elements that transfer energy to the water

Question 14

What are some applications of convection?

Answer 14

1. Electric Kettles: Heating element place at the bottom of the pot helps to facilitate the convection current
2. Hot Air Ballons: The burner at the bottom heats up the air above it, which hence starts a convection current

Question 15

What are some applications of Radiation?

Answer 15

1. Greenhouses: Sun’s radiation passes through glass and heats up the ground. The ground then becomes warm and re-radiates makes longer wavelength which cannot escape the glass and gets trapped
2. Global warming: same concept as greenhouse where earth is thought as a giant greenhouse. But due to human activities, we increase greenhouse gases in atmosphere and caused more radiation to be trapped therefore more heat.