ScienceYear 9

Year 9 Science – Change: Energy Transformations 1

Practise explaining heat transfer, tracing multi-step energy changes, interpreting bounce and pendulum data, and calculating thermal energy and efficiency. 20 questions. 25 minutes.

On a cold morning a student touches a metal rail and a wooden rail that are both at the same temperature. The metal feels much colder. Why?

Metal is at a lower temperature than the woodMetal radiates cold into the hand more than woodWood gives out more heat to the hand by convectionMetal conducts heat away from the hand faster than wood

A bungee jumper falls until the cord is fully stretched and the jumper stops for a moment at the lowest point. Which store holds most of the energy at that instant?

Kinetic energy of the jumperElastic PE in the stretched cordGravitational PE of the jumperThermal energy in the cord

A cyclist eats breakfast, then pedals to power a dynamo lamp on the bike. Which sequence shows the main energy changes from breakfast to lamp?

chemical → electrical → kinetic → light and thermalgravitational → kinetic → electrical → light and thermalchemical → kinetic → electrical → light and thermalchemical → kinetic → thermal → light only

Why does air warmed by a heater rise towards the ceiling?

Warmed air becomes less dense, so cooler, denser air pushes it upWarmed air gains mass, so the heater's radiation pushes it upCold flows into the air near the heater and pushes the warm air upWarmed air particles stop moving, so they float up through the room

A sealed metal flask of hot water is left on a bench and slowly cools. Which statement is correct?

No energy leaves, because a closed system blocks all transferEnergy and water vapour both leave through the sealed lidEnergy leaves the flask, but no water leavesCold enters the flask until the water and air match

Choose the word that completes each blank.

Energy from the Sun reaches a spacecraft by ₁, because space has no ₂ to carry the energy.

Blank 1: radiation · conduction · convection

Blank 2: gravity · light · particles

Choose the word that completes the blank.

An idealised vacuum flask that lets no energy or matter cross its boundary is an ₁ system.

Blank 1: open · isolated · closed

Choose the word and number that complete each blank.

A phone charger takes in 10 J and puts 7 J into the battery. The other 3 J becomes ₁ energy in the surroundings, so the total energy afterwards is ₂ J.

Blank 1: thermal · light · chemical

Blank 2: 3 · 10 · 7

Choose the word that completes each blank.

Water behind a dam stores ₁ PE. As it falls it gains ₂ energy, which a turbine changes into ₃ energy.

Blank 1: chemical · elastic · gravitational

Blank 2: thermal · kinetic · sound

Blank 3: electrical · light · chemical

10.

Circle 2 words in the sentence below.

A chain machine has these parts. Click the two that store potential energy before the machine starts.

raised-dominoesrolling-carstretched-bandmoving-block

11.

In a chain machine, a stretched rubber band launches a marble along a flat track. The marble hits a stack of cups and knocks them over. Which sequence of stores and transfers is correct?

Elastic PE → marble's KE → cups' KE and some thermalElastic PE → marble's GPE → cups' KE and some thermalChemical PE → marble's KE → cups' KE and some thermalElastic PE → marble's KE → cups' KE with no thermal

12.

A lid is placed on a cup of hot tea and the tea cools more slowly. Which statement best explains this?

The lid makes the tea particles lose kinetic energy fasterThe lid stops the tea conducting any energy to the cupThe lid stops all radiation leaving the surface of the teaThe lid traps warm air and vapour that would carry energy away

13.

The same ball is dropped from 1.00 m and rebounds to 0.64 m on its first bounce. What percentage of its gravitational PE was changed into thermal and sound energy during the bounce?

Drop height: 1.00 m. Rebound height: 0.64 m. Gravitational PE is proportional to height for the same ball.

64%36%32%72%

14.

A pendulum bob is released from a height of 20 cm. Which statement best explains the data?

Height reached on each swing (cm): swing 1 = 18, swing 2 = 16, swing 3 = 14.

Some energy is transferred as thermal energy to the air and pivot each swingGravity destroys some energy on every swingKinetic energy is permanently locked in the string as chemical energyThe bob gains mass as it swings, so it cannot rise as high

15.

Choose the word that completes each blank.

Coal stores energy that came originally from the ₁, captured by ancient plants through ₂.

Blank 1: Earth's core · Moon · Sun

Blank 2: photosynthesis · respiration · combustion

16.

Choose the word that completes each blank.

When a pot of water is heated from below, the water at the bottom becomes ₁ dense, so it rises and the cooler water ₂.

Blank 1: more · less · equally

Blank 2: rises further · evaporates · sinks

17.

Circle 2 words in the sentence below.

A student tests how drop height affects bounce height of a ball. Click the two variables that must be kept the same.

drop-heightball-usedfloor-surfacebounce-height

18.

A heater takes in 80 J each second. It gives out 60 J as wasted thermal energy to the room corners and the rest as useful energy. What is its efficiency?

75%25%33%20%

19.

In an energy flow diagram for a solar panel, 500 J of light arrives each second and 100 J leaves as electrical energy. The rest leaves as thermal energy. How wide is the thermal arrow compared with the electrical arrow?

Five times as wideThe same widthFour times as wideOne quarter as wide

20.

Circle 1 word in the sentence below.

A device takes in 250 J and gives out 200 J of useful energy. Click its efficiency.

20%80%125%50%

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Year 9 Science – Change: Energy Transformations 1