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Year 7

Changes of state: energy and evaporation

I can describe and explain what happens when a substance changes state and how evaporation occurs.

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New
New
Year 7

Changes of state: energy and evaporation

I can describe and explain what happens when a substance changes state and how evaporation occurs.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. States of matter can have differing amounts of energy.
  2. Solid states have the least energy, gas states have the most energy.
  3. A substance in its liquid state can evaporate at temperatures below its boiling point.
  4. The hotter the water, the more quickly it evaporates.
  5. Water evaporates at temperatures that are lower than 100℃.

Common misconception

Evaporation only occurs above the boiling point of a substance.

Give examples of substances other than water.

Keywords

  • Energy - Particles gain or lose energy when a substance changes state.

  • Evaporation - When a particle of a substance in the liquid state at the surface, has enough energy to change to the gas state and mix with air.

  • Evaporation rate - The evaporation rate is a measure of how quickly a substance evaporates.

  • Alcohol - Ethanol is a type of alcohol that has a higher evaporation rate than water.

Give a demonstration of 'spilled' acetone based nail varnish remover 'vs' water. Alternatively use alcohol based hand gel on the back of a hand to show evaporation.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.
Which state of matter has no fixed shape, but a definite volume and can flow?
An image in a quiz
Correct answer: a, liquid
b, solid
c, gas
Q2.
The point is the temperature at which a liquid turns into a gas.
Correct Answer: boiling
Q3.
Which state has the weakest forces of attraction between the particles?
solid
liquid
Correct answer: gas
Q4.
Which state of matter undergoes a change in volume when compressed?
solid
liquid
Correct answer: gas
Q5.
The two beakers below, with the same volume of water in each, were left in a room. Select all the true statements about Beaker A.
An image in a quiz
Dries up first.
Correct answer: Smaller surface area of water.
Correct answer: Less particles at the surface in touch with the air.
Wider than the other beaker.
The water is spread out over a greater area.
Q6.
It is winter. The bird bath in the school garden needs refilling. Some primary children discuss whether evaporation could be the reason that the bird bath is empty. Which reason is correct?
An image in a quiz
The sun is not powerful enough to dry up the the bird bath in the winter.
The sun evaporates the water in the summer but cannot in winter.
There are still sunny days in the winter which can dry up the bird bath.
Correct answer: Water can still evaporate even if the weather is not sunny.
Q5 UYSEG Q6 UYSEG

Exit quiz

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6 Questions

Q1.
Order the states of matter from lowest to highest energy.
1 - solid
2 - liquid
3 - gas
Q2.
Water can evaporate at temperatures lower than 100℃.
Correct answer: True
False
Q3.
What happens to the energy of a substance when it changes from a gas to a liquid?
Correct answer: It decreases.
It increases.
It remains the same.
Q4.
When changing from the solid to liquid to gas state, is required to overcome forces of attraction between particles.
Correct Answer: energy
Q5.
Which two substances are commonly used in thermometers and can change state at fairly low temperatures?
An image in a quiz
water
Correct answer: mercury
Correct answer: alcohol
salt solution
Q6.
Some students are revising the differences between boiling and evaporating, and they mix up their revision cards. Select all the statements below that are about evaporation.
Correct answer: A liquid is heated and the volume reduces, but no bubbles of gas form.
Correct answer: Some spilt water dries in a cold room.
Correct answer: A process that can take place at any temperature above melting point.
Cooking pasta in a pot of water that is producing a lot of bubbles of gas.
Forming a gas from a liquid, but a specific temperature needs to be reached.