# Thermal Conductors Investigation

In this worksheet, students will apply their knowledge of thermal conductors to investigating how heat moves.

Key stage:  KS 2

Curriculum topic:   Properties and Changes of Materials

Curriculum subtopic:   Comparing and Grouping Properties of Materials

Difficulty level:

### QUESTION 1 of 10

Heat is massively important to us - both in good ways and in bad.

We use heat energy to heat our homes and cook our food. We choose materials which allow heat to travel quickly and easily for these jobs.

Heat from the electric or gas ring travels through the pan to the egg.  Heat from the oil or water travels through the radiator into the air in the room.

Let's join young scientists Alfred and Ruby as they investigate thermal conductors and the science of heat transfer.

When we want heat to travel quickly and easily from one place to another, we make objects using which sort of materials?

wood

glass

plastic

metals

Choose THREE properties of many metals that make them good materials for frying pans?

strong

high melting point

electrical conductor

waterproof

Alfred and Ruby are two young scientists who want to investigate heat transfer.  They start with a question:

Which materials are good heat conductors?

They decide to use a mixture of water and crushed ice.

What is the temperature of the ice and water at the start of the test?

room temperature

100 degrees

0 degrees

They collect the other equipment they will need:

• paper cup
• metal cup
• plastic cup
• polystyrene cup

To keep their test fair, what must be the same about the cups?  Choose ONE answer.

shape and size

colour and pattern

all have handles

Which TWO other factors must they keep the same?

the air temperature (ambient)

who crushes the ice

the volume of the icy water

the freezer the ice comes from

Alfred decides to record his observations at the start of the investigation.

He notices that one cup feels very cold and has water droplets on the outside of it.  Which ONE do you think it might be?

the polystyrene cup

the metal cup

the plastic cup

all the cups are the same

the paper cup

Where have the water droplets come from?

tiny holes in the metal

the air

the ice

The scientific word to describe this change, when water droplets form on the side of the cup, is....

compensation

evaporation

condensation

Alfred and Ruby will measure the time it takes for the icy water to heat up to 10 degrees.

The students make a prediction:

Ruby says: "I think the icy water in the polystyrene cup will heat up quickest because it is a thin material."

Alfred says: "I think the icy water in the metal cup will heat up quickest because metal is a good heat conductor."

Whose prediction do you agree with?

Ruby

Alfred

Here is the table of results (the Time Taken column is how long it takes the water to increase from 0oC to 10oC):

 MATERIAL TIME TAKEN (mins) Metal 30 Plastic 45 Paper 50 Polystyrene 65

Which material is the POOREST thermal conductor?

metal

plastic

paper

polystyrene

Ruby says: "If metals are good thermal conductors, why does the radiator FEEL cold when the central heating is turned off?"

What do you think is the answer?

because it's colder than the room

we are not good at feeling temperature

the metal conducts heat away from our fingers

• Question 1

When we want heat to travel quickly and easily from one place to another, we make objects using which sort of materials?

metals
EDDIE SAYS
Yes, metals are good heat conductors. They are used where we want heat to travel quickly. The other three are all insulators and can be used to slow down the speed of heat transfer.
• Question 2

Choose THREE properties of many metals that make them good materials for frying pans?

strong
high melting point
waterproof
EDDIE SAYS
Strong and waterproof is definitely good for your frying pan, and many metals have high melting points, so they don't melt into a liquid mess on the stove! That's why you wouldn't have a frying pan made of lead: not only would it be very heavy but the metal would melt over the heat (and it's poisonous!).
• Question 3

Alfred and Ruby are two young scientists who want to investigate heat transfer.  They start with a question:

Which materials are good heat conductors?

They decide to use a mixture of water and crushed ice.

What is the temperature of the ice and water at the start of the test?

0 degrees
EDDIE SAYS
A mixture of ice and water measures 0 degrees centigrade. That's because the melting point of ice is 0°C and so the mixture will be at that temperature.
• Question 4

They collect the other equipment they will need:

• paper cup
• metal cup
• plastic cup
• polystyrene cup

To keep their test fair, what must be the same about the cups?  Choose ONE answer.

shape and size
EDDIE SAYS
The cups need to be able to hold the same amount of water/ice mixture and to be the same shape. That way, if there is any difference in the results, it won't be because the cups were different.
• Question 5

Which TWO other factors must they keep the same?

the air temperature (ambient)
the volume of the icy water
EDDIE SAYS
Water freezes at 0°C, but the temperature around it will affect the time it takes to melt. So the students must keep their cups in the same place to make the test fair. The volume (amount) of water must be the same as well.
• Question 6

Alfred decides to record his observations at the start of the investigation.

He notices that one cup feels very cold and has water droplets on the outside of it.  Which ONE do you think it might be?

the metal cup
EDDIE SAYS
You may know that metals are good conductors of both heat and electricity. Because of that, heat is quickly conducted away from the metal and into the ice/water mixture - that's why it feels so cold. Also, the air in the room has water vapour in it (from their breath, for example) and this condenses into little droplets when it touches the side of the metal cup. We'll find out about the others soon.
• Question 7

Where have the water droplets come from?

the air
EDDIE SAYS
The water on the outside of the metal cup has come from the air around it, because the air is warmer than the surface of the metal. Since the metal is so cold, the moist air has condensed into droplets of water on the side of the cup. You see this happening to your glass of ice cold fizzy drink on a hot day - makes it look very appetising!
• Question 8

The scientific word to describe this change, when water droplets form on the side of the cup, is....

condensation
EDDIE SAYS
When a gas changes to a liquid, it is called CONDENSATION - just like a steamy mirror in the bathroom when we have a shower.
• Question 9

Alfred and Ruby will measure the time it takes for the icy water to heat up to 10 degrees.

The students make a prediction:

Ruby says: "I think the icy water in the polystyrene cup will heat up quickest because it is a thin material."

Alfred says: "I think the icy water in the metal cup will heat up quickest because metal is a good heat conductor."

Whose prediction do you agree with?

Alfred
EDDIE SAYS
Remember that thermal conductors allow heat to travel easily from a warm place, the air, to a cool place, the icy water. Alfred has based his prediction on this understanding.
• Question 10

Here is the table of results (the Time Taken column is how long it takes the water to increase from 0oC to 10oC):

 MATERIAL TIME TAKEN (mins) Metal 30 Plastic 45 Paper 50 Polystyrene 65

Which material is the POOREST thermal conductor?

polystyrene
EDDIE SAYS
OK, looking at the results we can see that each one is different. The POOREST conductor is the one that moves the heat slowest of all, i.e. the one that takes the longest to allow the water to reach 10°C. As you can see from Alfred and Ruby's chart, the polystyrene cup took over an hour to do this, more than twice the time of the best conductor, the metal cup. Does that make sense?
• Question 11

Ruby says: "If metals are good thermal conductors, why does the radiator FEEL cold when the central heating is turned off?"

What do you think is the answer?

the metal conducts heat away from our fingers
EDDIE SAYS
Metals FEEL cold at room temperature because they are good thermal conductors. The metal conducts the heat away from our fingers, making them FEEL cold! On really cold days, or in really cold places, it can be dangerous to touch metal things (like railings) because they are so cold that your hand may freeze on to them. The heat is conducted away from your hand so quickly that your skin freezes (my, that's cold!).
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