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QUESTION 1

The continuous movement of water from the oceans to the air and back to the oceans is called the water cycle. The Sun heats the surface of the oceans, which causes the water to evaporate.

a) How does the rate of evaporation depend on

1. The wind speed (1)

2. The temperature (1)

3. The humidity? (1)

b) Explain how evaporation causes a cooling effect?(3)

QUESTION 1 ANSWER

The higher the wind speed the greater the rate of evaporation.

The greater the temperature the greater the rate of evaporation.

The higher the humidity, the slower the rate of evaporation.

b)

The most energetic molecules leave the surface of the liquid, so the

average energy of kinetic energy of the remaining molecules is less.

The temperature depends on the average kinetic energy, so it is

reduced.

QUESTION 2

Compare the similarities and differences between the process of conduction in metals and non-metals. (6)

In this question you will assessed on using good English, organising information clearly using specialist language where appropriate.

QUESTIONS 2 ANSWER

Similarities

Involve particles

Atoms vibrate causing neighbouring atoms to vibrate so energy is passed along.

Differences

Metals have free electrons

These collide with other free electrons and ions passing energy along.

This process is much more effective, so metals are better conductors.

QUESTION 3

In a hot water system water is heated by burning gas in a boiler. The hot water is then stored in a tank. For every 111 J of energy released from the gas, 100 J of energy is absorbed by the water in the boiler,

1. Calculate the percentage efficiency of the boiler. (4)

2. The energy released from the gas but not absorbed by the ‘boiler’ is wasted. Explain why this energy is of little use for further energy transfers. (1)

3. The tank in the hot water system is surrounded by a layer of insulation. Explain the effect of the insulation on the efficiency of the hot water system. (3)

QUESTION 3 ANSWER

1. Efficiency = 90%.

2. The energy becomes too spread out to use.

3. The insulation reduced the rate at which energy is lost from the tank to the surroundings. The water in the tank will stay hotter for longer. This increases the efficiency of the hot water system.

QUESTION 4

A light bulb transfers electrical energy into useful light

energy and wasted energy to the surroundings. For every

100 J of energy supplied to the bulb, 5 J of energy is

transferred to light.

Draw and label a Sanky diagram for the light bulb. (3)

QUESTION 4 ANSWER

The width of the arrow should be scaled to the number of

Joules.

QUESTION 5

A student uses some hair straighteners.

a) The straighteners have a power of 90 W. What is meant by ‘a power of 90 W’. (2)

b) Calculate how many kilowatt-hours of electricity are used when the straighteners are used for 15 minutes. (3)

c) The electricity supplier is charging 14 p per KWh. Calculate how much it will cost to use the straighteners for 15 minutes a day for one year. (2)

QUESTION 5 ANSWER

a) 90 Joules of energy are transferred every second.

b) E= 0.0225 KWh

c) Cost = £1.15

QUESTION 6

Fluorescent bulbs are being replaced by compact

fluorescent bulbs.

A 25 W compact bulb costs £12, a filament bulb costs

50p.

A 25 W compact bulb gives out as much light as a 100W

filament bulb.

A filament bulb lasts for about 1000 hours; a compact bulb

lasts for a about 8000 hours, although significantly shorter if

the bulb is turned on and off very frequently.

Compare the advantages and disadvantages of buying a compact fluorescent

bulb rather

than filament bulbs. (6)

QUESTION 6 ANSWERS

Advantages

• More efficient/4 times more efficient.

• Cheaper to use

• Last longer/lasts 8 times as long.

• Better for the environment.

Disadvantages

• More expensive to buy/cost 24 times as much to buy.

• Disposal a problem because of mercury vapour.

• Shortened lifespan if turned on and off very frequently.

QUESTION 7

Explain why step-up transformers are used in the

National grid (2)

QUESTION 7 ANSWER

To increase the voltage on the cables and reduce power

losses.

QUESTION 8

Electromagnetic waves travel at a speed of 300 000 000

m/s. BBC 4 is transmitted using a wavelength of 1500

metres.

Calculate the frequency of these waves. (3)Write down the equation you use. Show clearly how you

work out your answer and give the unit.

QUESTION 8 ANSWER

Frequency = 200 000 Hz.

QUESTION 9

Give one example of each of the following from everyday

life.

1. Reflection of light (1)

2. Reflection of sound (1)

3. Refraction of light (1)

4. Diffraction of sound (1)

We do not normally see the diffraction of light in everyday life. Suggest a reason for this (2)

QUESTION 9 ANSWER

1. Any example using mirror/water or a shiny smooth surface.

2. Any example of an echo.

3. Any example using a lens e.g. spectacles, cameras.

4. Any example of hearing sound around a corner.

The wavelength of light is very small, so diffraction only occurs when light passes through a narrow gap.

QUESTION 10

Red shift from distant galaxies provides evidence for the

big bang theory.

What is meant by red shift? (2)

Explain how red-shift provides evidence for the Big Bang

theory. (6)

QUESTION 10 ANSWERS

The wavelength of light from a galaxy is shifted towards

the red end of the spectrum and the galaxy is moving

away from us.

• Light from (most) galaxies is red shifted.

• The further the galaxy the bigger the red shift.

• The furthest galaxies are moving fastest.

• This shows that the universe is expanding.

• If the universe has always been expanding

• It must have once been very small.