Every card in Energy, Year 7: food, resources and temperature
The whole deck, in order — so you can read it through before your child ever sees it.
- On a food label, which unit is used for the energy in the food alongside kilocalories?
Kilojoules (kJ)
HintA thousand of the standard unit of energy.
WhyThe joule is the scientific unit of energy, and food stores so much that labels use thousands of them. Kilocalories are an older unit still printed beside it.
- Label A says 1,500 kJ per 100 g; label B says 600 kJ per 100 g. Which food stores more energy in each 100 g?
Food A
HintCompare like with like: both figures are for an equal mass.
WhyBoth labels quote energy for 100 g, so the numbers can be compared directly. Fatty and sugary foods have the highest values.
- A cereal provides 1,600 kJ per 100 g. How much energy is in a 50 g bowl?
800 kJ
HintThe bowl is half of the amount on the label.
Why50 g is half of 100 g, so it holds half the energy: 1,600 ÷ 2 = 800 kJ.
- Why does a person need more energy from food on a day spent hiking than on a day spent resting?
Active muscles transfer more energy
HintMoving the body uphill all day has to be paid for.
WhyThe energy stored in food is transferred when muscles move the body and keep it warm. More activity means more is transferred, so more has to be eaten.
- How many kilojoules are there in 5,000 joules? (number only)
5
Hint'Kilo' means the same as in kilogram and kilometre.
WhyThe prefix kilo- means a thousand, so 5,000 J ÷ 1,000 = 5 kJ. Food labels use kilojoules because food stores so many joules.
- An energy resource that will not run out because it is naturally topped up
A renewable resource
HintWind and sunlight are examples; coal is not.
WhyWind, sunlight, waves, tides and flowing water are all replaced by nature as fast as they are used.
- Coal, oil and natural gas formed from the remains of ancient living things, so they are known as ____ fuels.
fossil
HintThe same word names the remains of ancient life found in rocks.
WhyThey are non-renewable: they take millions of years to form and are being burned far faster than that.
- What is the main drawback of wind power as a source of electricity?
It is unreliable — the wind does not always blow
HintThink about a calm day.
WhyTurbines generate nothing in still air, so another source or a store of energy is needed as a back-up.
- A swimming pool at 30 °C or a teaspoon of boiling water: which stores more thermal energy?
The swimming pool
HintThink about how much water there is to warm up.
WhyThe teaspoon is hotter, but the pool contains millions of times more water. The total energy depends on the amount of material as well as how hot it is.
- What does temperature tell you about an object: how hot it is, or how much energy it stores?
How hot it is
HintA thermometer reads the same in a cup or a bath of the same water.
WhyTemperature is measured in degrees Celsius and energy in joules. A cup and a bath of water can be equally hot while the bath stores far more energy.
1★ KS3-PHYS-ENE-0030
2★ KS3-PHYS-ENE-0031
3★ KS3-PHYS-ENE-0032
4★ KS3-PHYS-ENE-0033
5★ KS3-PHYS-ENE-0034
6★ KS3-PHYS-ENE-0035
7★ KS3-PHYS-ENE-0036
8★ KS3-PHYS-ENE-0037
9★ KS3-PHYS-ENE-0038
10★ KS3-PHYS-ENE-0039
Keep what you learn
Here, nothing is saved. In your child’s own sky every card is scheduled — it comes back just before they’d forget it — and the professor who wrote it is one tap away.