1. Certain foods are treated with gamma radiation. A high does can be used to kill bacteria that makes food turn bad. A low dose can be used to slow down the ripening process in fruit and vegetables.
   1. 1. Explain what gamma radiation is
      2. The food that’s treated using gamma radiation is packed inside crates. Why does a source that emits gamma radiation have to be used?
   2. One suitable source is the isotope caesium 137.
      1. What are isotopes?
      2. The gamma source that treats the food is contained behind concrete walls. Explain how the concrete walls protect the workers from the radiation.
   3. Some people chose not to be buy food that’s been treated by radiation.
      1. Why is it important that consumers know which foods are treated with radiation?
      2. How could a scientist prove that food treated in this way is safe?
2. Electricity is distributed from power station to consumers via the National Grid
   1. A transformer is made from a primary coil, a secondary coil, and an iron core.
      1. What are the coils composed of?
      2. When the primary coil has an alternating current in it what’s produced in the core?
      3. Explain what a step-down transformer does.
      4. Why is a step-down transformer used in the National Grid?
   2. Most power stations burn fossil fuels.
      1. Name one fossil fuel.
      2. Complete the sentence below.
      3. Burning fossil fuels produces ________ gases that increase _________ warming.
3. Electricity can also be produced using renewable sources.
   1. What is meant by a renewable energy source?
   2. Give two examples of renewable energy.
4. The table below different ways in which a home can reduce their energy consumption.
   1. Over a 5-year period, which is the most cost effective method. Show all your workings.

1. Another way to save energy is to use an energy-efficient light bulb as opposed to an ordinary one. Below is a table with two different light bulbs. Each bulb produces the same useful power output.
   1. Calculate the useful power output (light) of the filament bulb.
   2. Sketch a Sankey diagram for the filament bulb.
   3. Calculate the efficiency of the LED bulb.

1. A car breaks down. The two passengers get out to push it.
   1. Person A pushes with a force of 60N and person B with a force of 40N.
      1. What is the total force of person A and person B on the car?
      2. Complete the sentence choosing the correct word below:
         The total force is the __________ force of both people pushing the car. mean resultant medium
      3. The car is pushed at a constant speed for 25 metres. Use the equation below to calculate the work done to push the car 25 metres. Show how you worked out your answer.work done = force applied x distance moved in direction of force
   2. Choose the correct word under each sentence to complete the sentence.
      1. Most work done to push the trolley is transformed into ___________.
         light, heat, sound
      2. The unit of work done is the ____________.
         newton, watt, joule
2. Below are the stages for the life cycle of a star
   1. Write down the correct order for each stage. The first stage is already given.
      A. The cloud is pulled together by gravity. B. In space there are massive clouds of dust and hydrogen gas called nebula. C. The star gets hotter and expands. The outer part explodes as a supernova. Hot gas and dust are thrown into space. D. Helium nuclei form when hydrogen nuclei join together. E. The hydrogen runs out and the star expands to become a red giant. B ___ ___ ___ ___
   2. 1. Explain the relationship between the masses of nebulas (stage B) and the force of gravity between them.
      2. Explain the relationship between the distance between nebulas and the force of gravity between them.
   3. A star can remain in stage D for millions of years. Explain how.

ANSWERS

1. 1. 1. Correct: It’s an electromagnetic wave/radiation
         Incorrect: ‘Frequency’ isn’t acceptable
      2. Correct: Gamma radiation is able to penetrate the crate.
         Correct: Gamma radiation can pass through to the food.
         Incorrect: Gamma radiation kills bacteria.
   2. 1. Correct: The atoms of an element which have different numbers of neutrons.
         Correct: They have the same proton number but different mass numbers.
      2. Correct: It absorbs the gamma radiation.
         Correct: It stops the gamma radiation.
         Correct: It reduces the gamma radiation.
   3. 1. Correct: So they can decide if they want to eat food treated with radiation or not.
         Correct: It could be against they religious/moral views.
         Correct: Some people prefer food that’s not been tampered with at all.
         Incorrect: They don’t like the idea of eating treated food.
         Incorrect: They might be allergic to the food.
         Incorrect: They think it might make them ill.
      2. Correct: provide a comparison plus a reason.
         Test the food on humans/animals then measure the ill effects/monitor their health
         Monitor people that have eaten the food.
2. 1. 1. Insulated wire
      2. Correct: A magnetic field/magnetic force/magnetism which is alternating.
         Correct: A magnetic field/magnetic force/magnetism in which the direction /strength of the field changes/varies.
      3. A transformer that decreases the voltage.
      4. Step-down transformers are needed to reduce the voltage to a safe value for consumers to use.
   2. 1. Correct: Coal
         Correct: Oil
         Correct: Gas
      2. Burning fossil fuels produces greenhouse gases that increase global warming.
3. 1. It comes from a source that’s constantly being renewed.
   2. Correct: Tides
      Correct: Waves
      Correct: Wind
      Correct: Solar
      Correct: Geothermal
      Incorrect: Don’t simply say ‘water’
4. 1. Show all your workings clearly.
      135 x 5 – 350 = £325 10 x 3 – 80 = -£50 300 x 5 – 2000 = -£500 55 x 5 – 240 = £35 Answer: cavity wall installation
   2. 1. efficiency = useful power out / total power in
         useful power out = (60 x 2.5) / 100 = 1.5 W Make sure to use the right substitution. Writing the equation out will help.
      2. You only need to sketch it so don’t worry about drawing it to scale. However, make sure your arrows have appropriate widths and label them.
      3. Useful power out = power in x efficiency
         60 x 2.5 = 10 x ELED Efficiency of LED = 15% Remember from the text that each bulb produces the same useful power output.
5. 1. 1. The total force is the sum of both forces.
         40 + 60 = 100N
      2. Resultant force
      3. Substitute in carefully
         100 x 25 = 2500
   2. 1. Heat
      2. Joule
6. 1. B A D E C
      Remember to read each description carefully.
   2. 1. The bigger the masses of the nebulas the bigger the force of gravity between them.
      2. The greater the distance between the nebulas the smaller the force of gravity between them.
      3. Correct: The radiation pressure and gravity are in balance/equilibrium.
         Correct: There is enough/a lot of hydrogen to last for a very long time.
         Incorrect: Don’t use the word ‘equal’.