Year 5 Science: Thermal conductivity
Part of the Year 5 Science properties and uses of materials chapter. Chapter overview · whole chapter on one page
Thermal conductivity
A material that lets heat pass through it easily is a good thermal conductor. Metals are good conductors of heat. Wood and plastic are poor conductors, so they are used for handles.
In a fair test, three spoons are put into warm water with a drop of butter on each bowl. The spoon that conducts heat best moves the heat up to the butter fastest, so the butter melts and slides off sooner.
The results of a class test are in the table. Each spoon was put in warm water in the same way, with the same amount of butter.
| Spoon | Seconds for the butter to melt and slide off |
|---|---|
| metal spoon | 40 |
| plastic spoon | 150 |
| wooden spoon | 180 |
Key ideas
- A good conductor of heat moves heat quickly through the material.
- In the spoon test, the metal spoon was fastest, because metals conduct heat well.
- Wood and plastic are poor conductors of heat, so they make good handles.
- A fair test keeps the water, the butter and the spoons the same.
Method. Find the shortest time.
- Read the times. The metal spoon took 40 seconds, the plastic spoon 150 seconds, and the wooden spoon 180 seconds.40, 150, 180
- Choose the shortest. The shortest time is 40 seconds, for the metal spoon.metal spoon
- Write the answer. metal spoon
Check. The metal spoon conducts heat best. ✓
Method. Subtract the metal spoon time from the wooden spoon time.
- Read the two times. The wooden spoon took 180 seconds, and the metal spoon took 40 seconds.180 and 40
- Subtract. The difference is 180 minus 40, which is 140.180 - 40 = 140
- Write the answer. 140
Check. Check: 40 + 140 = 180. ✓
Watch out. Subtract the smaller time from the larger time.
Method. Read the results and the key ideas.
- Read the key idea. Wood and plastic are poor conductors of heat.poor conductors
- Choose the answer. So wood is a poor conductor of heat.poor conductor
- Write the answer. poor conductor
Check. The wooden spoon was the slowest in the test. ✓
Watch out
Watch out: a metal spoon feels hot because it conducts heat to your hand. The metal did not make the heat. Only fair tests show which material conducts heat best.
Try it (with your teacher). Use warm tap water (not hot), a metal spoon, a plastic spoon and a wooden spoon. Put a small piece of butter on the bowl of each spoon, and stand them in warm water in the same way. Time how long the butter takes to melt and slide off. Keep your hands out of the hot water, and be careful with the spoons.
Exam tip
Grown-up tip. Ask: “Which spoon was fastest? Why do you think the wooden handle feels cool?” Let your child keep the test fair by changing only the spoon.
Exercise 5C Thermal conductivity
Method. Find the shortest time in the table.
- Read the times. The metal spoon took 40 seconds, the shortest time.40 seconds
- Name the spoon. So the metal spoon melted the butter fastest.metal spoon
- Write the answer. metal spoon
Check. Metals conduct heat well. ✓
Method. Find the longest time in the table.
- Read the times. The wooden spoon took 180 seconds, the longest time.180 seconds
- Name the spoon. So the wooden spoon took the longest.wooden spoon
- Write the answer. wooden spoon
Check. Wood is a poor conductor of heat. ✓
Method. Read the row for the plastic spoon.
- Read the row. The plastic spoon row shows 150 seconds.150
- Write the number. So the plastic spoon took 150 seconds.150
- Write the answer. 150
Check. The plastic spoon took longer than the metal spoon. ✓
Method. Subtract the metal time from the plastic time.
- Read the times. The plastic spoon took 150 seconds, and the metal spoon took 40 seconds.150 and 40
- Subtract. The difference is 150 minus 40, which is 110.150 - 40 = 110
- Write the answer. 110
Check. Check: 40 + 110 = 150. ✓
Method. Read the key ideas in section 5.3.
- Read the key idea. A good conductor of heat moves heat quickly through the material.moves heat quickly
- Fill the gap. So the missing word is quickly.quickly
- Write the answer. quickly
Check. Metals are good conductors of heat. ✓
Method. Read the key ideas in section 5.3.
- Read the key idea. Wood and plastic are poor conductors of heat.poor conductors
- Give the answer. So they are poor conductors.poor conductors
- Write the answer. poor conductors
Check. This is why wooden and plastic handles stay cool. ✓
Method. Think about which material conducts heat poorly.
- Think about the handle. A wooden handle is a poor conductor, so it stays cool.stays cool
- Choose the spoon. So a wooden spoon is the better choice.wooden
- Write the answer. wooden
Check. The wooden handle is cooler to hold. ✓
Method. Find the longest time.
- Find the longest. The longest time is 180 seconds, for the wooden spoon.180
- Write the number. So the slowest spoon took 180 seconds.180
- Write the answer. 180
Check. The wooden spoon was the slowest. ✓
Method. Think about what makes the test fair.
- Think about the test. Only the type of spoon should change.type of spoon
- Write one thing. The water temperature, the butter and the bowl size must stay the same.stay the same
- Write the answer. Accept any one of: the same amount of water, the same amount of butter, the same size of spoon bowl.
Check. Changing only the spoon keeps the test fair. ✓
Method. Think about how heat moves through each spoon.
- Think about the metal. Metal conducts heat well, so heat moves up to the handle.conducts heat well
- Think about the wood. Wood is a poor conductor, so the handle stays cool.poor conductor
- Write the answer. Accept any sentence that says metal conducts heat well to your hand, but wood is a poor conductor, so the wooden handle stays cool.
Check. Heat moves through metal much more quickly. ✓