P1 - Energy Transfer By Heating

Question 1

What type of energy transfer is infrared radiation?

Answer 1

Electromagnetic

Question 2

The hotter the object the ________ infrared radiation is emitted.

Answer 2

More

Question 3

Does infrared use particles? And give a real life use of this

Answer 3

No

The sun travelling through a vacuum (space) to earth

Question 4

Why are houses in hot countries painted white?

Answer 4

White, shiny surfaces emit and absorb heat radiation less quickly than dull black surfaces

Question 5

How is the arrangement of particles in a liquid different from those in a solid

Answer 5

Solids vibrate around a fixed point and so have a fixed shape. Liquid particles are in contact but can move freely and so doesn’t have a fixed shape and can flow.

Question 6

How does conduction occur?

Answer 6

One end of the solid is heated, the particles gain kinetic energy and vibrate more. This energy is passed to neighbouring particles and is transferred throughout the solid.

Question 7

What is conduction like in metals

Answer 7

When metals are heated their particles free electrons gain kinetic energy and move throughout the metal transferring energy by colliding with other particles. Hence why metals are good conductors

Question 8

What is convection

Answer 8

When a fluid is heated it expands, becomes , less dense and rises, this is replaced by cool liquids, becomes more dense and falls, creating a flowing convection current. (Hence why it can only be in liquids and gases).

Question 9

What’s evaporation

Answer 9

Liquid to gas

The more energetic particles gain energy and leave the liquid leaving an average lower temperature. Evaporation causes cooling

Question 10

How to increase the rate of evaporation?

Answer 10

• increase surface area of the liquid
• breeze over the top
• increase the temperature of the liquid

Question 11

What’s condensation

Answer 11

Gas to liquid

Takes place on cold surfaces

Question 12

How to increase rate of condensation

Answer 12

Decrease temperature

Increase surface area

Question 13

How to increase the rate of energy transfer

Answer 13

Increase the temperature difference between the two mediums

Question 14

What does energy transfer rate depend upon other than temperature difference

Answer 14

The materials

The shape

The surface area

Question 15

How to maximise energy transfer?

Answer 15

Dull Matt black surfaces

Good conductors (metals)

Question 16

Explain how a vacuum flask works

Answer 16

Double wall with vacuum prevents conduction/convection as there’s no particles

Inside the drink the walls are silver to reflect the radiation back into the drink

Silvered outside to reduce the heat emitted from conduction and radiation

Question 17

The grater the mass the more _________ it takes to heat it

Answer 17

Slowly

Question 18

What affects the rate of temperature change in a substance?

Answer 18

Energy transferred to it

Mass

Specific heat capacity

Question 19

What’s the specific heat capacity equation and units

Answer 19

E = m x c x @

E - energy transferred (Joules)
M - mass (KG)
C - specific heat capacity (sometimes 4.2) (J/kg degrees)
@ - temperature change (degrees)

Question 20

Describe a few ways to minimise energy loss through the house

Answer 20

Fibreglass loft (good insulator, stops conduction)

Double glazing (stops convection)

Cavity wall (convection - traps air in small air bubbles)

Question 21

What’s a U value?

Answer 21

How much energy per second is transferred

The lower the u value the better the insulator

Question 22

Why is fibreglass a good insulator?

Answer 22

Contains trapped air