Year 7 Science
Matter
Lesson 2
Getting Hot - Changing State
From the last lesson you know that the three States of Matter are:
Solid
Liquid
Gas
Activity 1
You can change the state of a substance by heating or cooling.
The example below is water.
Copy the diagram above and include the following words in the best places:
melts
evaporates
freezes
condenses
At what temperature will ice change to liquid water?
At what temperature will liquid water change to steam?
At what temperatures will the reverse changes happen?
Click here for the online version.
Activity 2
Different substances change state at different temperatures.
Here is a table of substances and their melting points. Copy the table and use the information to work out whether each substance is a solid or liquid at room temperature (20 degrees celsius).
Substance
Melting Point (degrees celsius)
aluminium
660
mercury
-39
ice
0
copper
1083
sugar
161
carbon (diamond)
3550
wax
100
Is there enough information in the table to be sure that the liquids have not turned to gases?
What other information will you need to be certain?
You maybe able to find this information.
Which substance in the table would be used for the following?
Saucepan
Candle
In a thermometer
Water pipe
Activity 3
Place an ice cube into a beaker and cover with cling-film.
Next quickly using a balance find the mass of the beaker and the ice.
Leave the beaker in a warm place.
When the ice has completely melted find the mass of the beaker again.
Prediction - If the ice and beaker had a mass of 210g. What do you expect the mass of the water and beaker to be?
Does changing the state of a substance change its mass?
Can you think of any reasons for your answer?
A student noticed that the inside of the beaker had become misty. She explained to the teacher that she had placed the beaker near to a hot radiator and some of the water had evaporated.
Her partner had predicted that this would cause the mass to drop as some of the water was now a gas. He said, "gases don't have any mass"
What do you think?
Click here for some of their results.
Activity 4
When things get hot or cool down they do not always change state. It depends whether the temperature is anywhere near their melting or boiling points.
So what does happen to a solid, a liquid or a gas when it gets hot?
They get bigger!
Try these experiments
You know something about changes of state like melting and boiling and that different substances change state at different temperatures.
You also know that even if you heat a substance and it does not change state something still happens. They increase in size. You might see this as an increase in length, width or volume.
Remember they may get bigger but they do not get heavier. The mass stays the same.
Return to Key Stage 3 Science
