How to play Energy Stores
Energy Stores is a game about energy stores and the ways energy moves between them. Each question shows an everyday scene, such as a ball falling or a pan of water on a camping stove. You answer it in steps, with four choices at each step.
First you pick the store that empties. Then you pick the store that fills. Next you choose how the energy is transferred: by mechanical work, electrical work, heating or radiation.
From scene 4 onwards, a fourth step asks for the efficiency. The game gives you the useful output energy and the total input energy in joules. You work out the efficiency as a decimal or as a percentage, whichever the question asks for.
A round has ten scenes. Each right step scores 10 points, with 5 more if you answer within 15 seconds. When a step goes wrong, the game shows the right answer before you move on. The harder start puts the efficiency step into every scene from the first one. Practice mode turns the timer off.
The science behind energy stores and transfers
Physicists describe energy as sitting in different stores. A moving object has energy in its kinetic store. Lifting an object fills its gravitational potential store, and stretching a spring or a rubber band fills its elastic potential store. Fuels, food and batteries have chemical stores, and a hotter object has more energy in its thermal store. The game also uses the magnetic, electrostatic and nuclear stores.
When something changes, energy moves from one store to another. Energy is never made or destroyed, so the total stays the same. Think of a person lifting a box onto a shelf. The chemical store of the person empties, and the gravitational potential store of the box fills. The energy moves by mechanical work, because a force moves the box.
Four pathways carry energy between stores. Mechanical work happens when a force moves an object. Electrical work happens when a current flows. Heating moves energy from a hotter object to a cooler one. Radiation carries energy as waves, such as light and infrared.
No transfer is perfect. Some energy always spreads into the surroundings, often as a small rise in temperature, and is then hard to use again. People call this energy wasted, or dissipated. Efficiency tells you what fraction of the input energy goes where you want it. If a device takes in 800 J and 600 J of that is useful, the efficiency is 600 ÷ 800 = 0.75, or 75%. An efficiency can never be more than 1, or 100%.
AQA (8463) covers energy stores and systems in section 4.1.1.1 and efficiency in 4.1.2.2, where students may give an efficiency as a decimal or a percentage. Edexcel (1PH0) covers the way energy is stored in Topic 3, conservation of energy, with the efficiency equation at point 3.11. OCR Gateway (J249) covers stores in P7.1 and efficiency in P7.2. OCR Twenty First Century (J259) names eight ways energy can be stored and says energy moves between them by working and heating.
Tips for energy store questions
- Look for the store that is full at the start. A lifted ball, a stretched band or a wound spring has energy ready to move.
- Name the object as well as the store, such as the thermal store of the water. It makes your answer clear.
- Heating is a pathway. The store that heating fills is called the thermal store.
- For efficiency, the useful energy goes on top of the fraction. If your answer is bigger than 1, you have flipped it.
- To turn a decimal efficiency into a percentage, multiply by 100, so 0.65 becomes 65%.
- Wasted energy is the total input minus the useful output. Keep it out of the top of the fraction.
Speed only adds 5 points to a step. A wrong step loses the 10 points and your streak, so study the scene before you choose.
Use Energy Stores in the classroom
Energy Stores suits Years 9 to 11 and works at the start of an energy topic or as revision before a test. A round of ten scenes takes under ten minutes.
Show a scene on the board and give students thirty seconds to write the emptying store, the filling store and the pathway before anyone picks. Then compare answers. The wrong options come from real mix-ups, such as swapping the store that empties with the one that fills. Ask students to explain why each wrong store does not fit the scene. After the round, ask them to find one more example of each change in the room around them, such as the spring in a door closer or a radiator warming the air.
For a quick efficiency check, tick the harder start so every scene ends with the calculation. Practice mode switches off the timer for students who need more time to think.
Students need no account, and the game runs in any up-to-date browser. The teachers page explains how the games fit into lessons, and the page for parents covers use at home.
Similar games
Find more on the games page. Equation Rearranger includes energy equations such as kinetic energy and gravitational potential energy. Unit Sprint helps with the energy units kJ, MJ and kWh.
Questions people ask
These questions come up often when students first meet energy stores.
What are the energy stores in GCSE physics?
The stores in this game are kinetic, gravitational potential, elastic potential, thermal, chemical, magnetic, electrostatic and nuclear. Check your own board's specification for the list it uses.
What is the difference between an energy store and an energy transfer?
A store is where energy is kept, such as the kinetic store of a moving car. A transfer is how energy moves from one store to another: by mechanical work, electrical work, heating or radiation.
How do you calculate efficiency as a percentage?
Divide the useful output energy by the total input energy, then multiply by 100. A lamp that transfers 30 J usefully for every 200 J it takes in has an efficiency of 30 ÷ 200 = 0.15, or 15%.
Is heat an energy store?
No. The store is called the thermal store. Heating is one of the ways energy moves into or out of a thermal store.