1.3 Making Use of Energy

Question 1

What are the primary mechanisms of heat energy transfer?

Answer 1

Conduction, convection, and radiation.

Question 2

How does conduction occur in solids?

Answer 2

Through the vibration of atoms, where energy is transferred from one atom to the next as they vibrate more vigorously with increased temperature.

Question 3

Why are metals better conductors of heat than non-metals?

Answer 3

Metals have free (delocalized) electrons that gain kinetic energy when heated and transfer energy quickly through collisions with adjacent metal ions and other electrons, facilitating faster heat diffusion.

Question 4

What is convection and where does it primarily occur?

Answer 4

Convection is the transfer of heat in fluids (liquids and gases) where heated particles move to take the place of cooler particles, creating convection currents.

Question 5

What role do surfaces play in radiation?

Answer 5

Black, matt surfaces are good emitters and absorbers of radiation, while light, shiny surfaces are poor emitters and absorbers.

Question 6

How can heat loss be reduced in buildings?

Answer 6

By using methods like double glazing, cavity wall insulation, and loft insulation, which reduce conduction, convection, and radiation.

Question 7

What is the payback time formula for energy-saving methods?

Answer 7

Payback time = Installation Cost / Annual Saving.

Question 8

How does double glazing reduce heat loss?

Answer 8

It contains a layer of air or a vacuum between two panels of glass, reducing conduction and preventing convection.

Question 9

What is cavity wall insulation and how does it work?

Answer 9

Insulating material placed in the gap between the outer bricks and the inside wall, containing pockets of trapped air that reduce conduction and convection.

Question 10

What is the function of a thin layer of silver foil in cavity wall insulation?

Answer 10

To reduce heat loss via radiation by reflecting heat back into the building.

Question 11

How does loft insulation reduce heat loss?

Answer 11

It reduces heat loss via convection and conduction through the roof, similar to cavity wall insulation.

Question 12

What is the effect of heat on fluid particles?

Answer 12

Heated fluid particles move faster and expand, becoming less dense and causing hot material to rise.

Question 13

How is the density of an object calculated?

Answer 13

Density is calculated as mass per unit volume: ρ = m / V.

Question 14

How does convection create weather systems?

Answer 14

Convection cells on a large scale cause hot air to rise and cool air to fall, leading to the movement of air and weather patterns.

Question 15

How does conduction differ in metals and non-metals?

Answer 15

In metals, conduction involves both vibration of ions and movement of free electrons, while in non-metals, it only involves the vibration of atoms.

Question 16

Why are gases less dense than solids and liquids?

Answer 16

Gases have particles that spread out to occupy a greater volume, resulting in lower density.

Question 17

How can irregular objects’ volume be measured?

Answer 17

By using the water displacement method in a measuring cylinder.

Question 18

Why is reducing heat loss in buildings good for the environment?

Answer 18

It reduces the amount of energy required to heat the house, leading to lower energy consumption and reduced carbon emissions.

Question 19

What is the primary method of heat transfer in solids?

Answer 19

Conduction.

Question 20

What type of surfaces are poor emitters and absorbers of radiation?

Answer 20

Light, shiny surfaces.

Question 21

How does the movement of hot fluid particles affect cooler areas?

Answer 21

Hot fluid particles move into cooler areas, transferring heat and causing convection currents.

Question 22

How does heat transfer via radiation occur?

Answer 22

Through infrared electromagnetic waves, which can transfer energy without requiring particles.

Question 23

Why is air considered a poor conductor of heat?

Answer 23

Air has low thermal conductivity due to the large distance between its molecules compared to solids and liquids.

Question 24

What is the role of free electrons in metal conduction?

Answer 24

Free electrons in metals gain kinetic energy when heated and transfer energy quickly through collisions with adjacent ions and other electrons.

Question 25

What is the main reason metals conduct heat better than non-metals?

Answer 25

The presence of free (delocalized) electrons in metals allows for faster energy transfer.

Question 26

How do black, matt surfaces behave with radiation compared to light, shiny surfaces?

Answer 26

Black, matt surfaces are good emitters and absorbers, while light, shiny surfaces are poor emitters and absorbers of radiation.

Question 27

What happens to fluid density when heated?

Answer 27

Heated fluid particles expand, making the fluid less dense and causing it to rise.

Question 28

What is the effect of a vacuum in double glazing?

Answer 28

It prevents heat loss via conduction and convection.

Question 29

What method can be used to measure the volume of a regular object?

Answer 29

By measuring its dimensions (length, width, height).

Question 30

What are insulators and how do they function?

Answer 30

Insulators are materials that are poor conductors of heat, reducing heat transfer by limiting conduction.

Question 31

How can carpets and curtains contribute to reducing heat loss?

Answer 31

They act as additional insulating layers, reducing heat loss through floors and windows.

Question 32

Why does hot fluid tend to rise in a convection current?

Answer 32

Hot fluid is less dense than cold fluid, causing it to rise and be replaced by cooler fluid.

Question 33

How does loft insulation specifically reduce heat loss through the roof?

Answer 33

By trapping air and reducing heat transfer via conduction and convection.

Question 34

What are the benefits of retrofitting energy-saving methods in a building?

Answer 34

It reduces heat loss, lowers energy consumption, and can be cost-effective with a shorter payback time.

Question 35

Why is reducing energy loss important for cost-effectiveness?

Answer 35

It lowers heating costs and can save money over time by reducing the amount of energy required to maintain a comfortable temperature.

Question 36

What are the main methods of heat transfer that can be reduced to improve building insulation?

Answer 36

Conduction, convection, and radiation.