الأسبوع 12 · المحور الثاني، الوحدة الثانية، المفهوم 2.2 «الطاقة والحركة» (ب): طاقة الوضع وطاقة الحركة وتحولات الطاقة · 3 دروس
3
Energy changing form
Discovery Education Science P4: Term 1, Unit 2, pp. 145–157
GoalDescribe energy changes in toys, tools and the roller coaster, and write a claim, evidence and reasoning.
New words
energy change · when energy turns from one form into anotherchemical energy · energy stored in food, fuel and batteriesclaim · a one-sentence answer to a science question
Explanation
Energy is changing form all around us. A fan changes electrical energy into the energy of moving blades. A torch changes the chemical energy stored in its battery into light and a little heat. A gas cooker changes the chemical energy of the gas into heat for cooking. A car engine changes the chemical energy of petrol into motion, with some heat and sound as well. A roller coaster is lifted up the first hill: that gives it potential energy. As the train rushes down, the potential energy changes into kinetic energy, and the train goes faster. To explain a science question, we write a claim (a one-sentence answer), evidence (facts that support it) and reasoning (why the evidence supports the claim).
Device
Energy in
Energy out
fan
electrical
motion
torch
chemical (battery)
light and heat
gas cooker
chemical (gas)
heat and light
car engine
chemical (petrol)
motion, heat and sound
Worked examples
Farida presses the switch of a ceiling fan. The electrical energy changes into the energy of the turning blades, and the air moves.
pulled up the hill→top: most stored energy→going down: motion energy
On a roller coaster, the train is pulled up the first hill. At the top it has the most potential energy. Going down, this changes into kinetic energy, so the train speeds up.
Claim
Evidence
Reasoning
speed comes from stored energy
lifted high, then speeds up
potential becomes kinetic
Claim, evidence, reasoning for the roller coaster. Claim: the train gets its speed from stored energy. Evidence: it is pulled to the top of a tall hill, then it speeds up with no engine pushing. Reasoning: the lifted train has potential energy, and as it goes down that energy changes into kinetic energy.
Class activity
Energy change hunt. With a grown-up, find three devices at home that change energy: a lamp, a fan, a radio. Never touch sockets or plugs. Draw each as a box and write the energy in and the energy out, like this: lamp, electrical in, light and heat out. Which device also gives out some heat? Hold a hand near it, never touch a hot bulb.
Practice
1
A torch is switched on. What energy goes in and what comes out?
Chemical energy from the battery goes in; light (and a little heat) comes out.
2
A toy car with a squeezed spring is let go. Which energy changes into which?
Potential energy in the spring changes into kinetic energy.
3
Which energy change does the gas cooker make? Say the letter.
Letter
Change
A
sound to light
B
chemical to heat
C
light to sound
B: chemical energy to heat.
4
In a scientific explanation, what are the three parts?
