☰ خطة العام · العلوم (بالإنجليزية)

Term 2 review: energy and shifting surfaces

الأسبوع 30 · مراجعة الفصل الدراسي الثاني: الطاقة والوقود والأسطح المتغيرة · 3 دروس
1

Review: energy, devices and fuels

Discovery Education Science P4: Term 2, Units 3–4
GoalRevise energy chains, input and output, fuels, fossil fuels and pollution with new tasks.
New words
energy chain · the steps that show how energy passes from its source to a userenewable · can be replaced or used again and againfossil fuel · coal, oil or natural gas, formed from ancient living things
Explanation

Let us remember what we learned about energy. A device needs an energy source, such as a battery, the Sun or a fuel. An energy chain shows how the energy changes form: for example, chemical energy in a battery becomes electrical energy and then light. Every device has an energy input and a useful output, and some energy becomes wasted heat or sound, but energy is never lost or used up. Fuels such as petrol, wood, coal, oil and gas store chemical energy. Coal, oil and natural gas are fossil fuels, made from ancient living things over millions of years, so they are nonrenewable. Burning them makes pollution and carbon dioxide, so we should use fuel wisely. Wood and biofuels can be renewable if new plants grow to replace what we use.

IdeaRemember
energy chainsource → forms of energy → use
energy is never lostsome becomes heat or sound
fossil fuelsnonrenewable; burning pollutes
using fuel wiselysave it and choose renewable energy
Worked examples
A new chain. Omar’s torch has a battery. The battery stores chemical energy. When he switches on, the bulb receives electrical energy and gives out light, and a little heat that is wasted.
FuelRenewable?
coalno
natural gasno
biofuelyes
wood from a replanted forestyes
Sort the fuels. Coal, oil and natural gas will run out one day: nonrenewable. Wood from a forest that is replanted, and biofuel made from plants, can be replaced: renewable.
TankKm per litreDistance
30 litres12360 km
Fuel sums. Mariam’s family car has a full tank of 30 litres and drives 12 km on each litre. On a full tank it can go 30 × 12 = 360 km. If the trip is 450 km, they need 450 − 360 = 90 km more, so they must stop for fuel.
Class activity

Energy poster. On one page, draw an energy chain that starts at the Sun and ends with a light in your home (for example the Sun, a plant, a fossil fuel, a power plant, a lamp). Label each form of energy. In a box write two ways your family uses less fuel or electricity, such as switching off lights or walking short trips.

Practice
1
A hair dryer has electrical input. Name one useful output and one wasted output.
2
Why are coal, oil and natural gas called fossil fuels?
3
A car uses 5 litres for 60 km. How many km on 1 litre?
4
Give two ways to use fuel wisely.