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Year 7

Pure substances

I can describe the difference between a pure substance and a mixture.

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New
New
Year 7

Pure substances

I can describe the difference between a pure substance and a mixture.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. A pure material is made of only one type of substance
  2. A pure material has a fixed melting point and boiling point
  3. Impurities change the melting and boiling point of a material
  4. A mixture contains two or more types of substances which can be easily separated
  5. Mixtures melt or boil over a range of temperatures

Common misconception

Pupils mistake common (everyday) usage of pure (i.e. 'pure orange juice) as being a pure substance

'Everyday' usage refers to one *source* whereas scientific usage refers to particle composition. Take particular care when discussing water.

Keywords

  • Pure substance - A pure substance contains only one type of chemical

  • Mixture - A mixture is a material that contains two or more different substances which can be physically separated

  • Impurity - An impurity is a chemical that is found in a material in very small amounts, but can change the material's properties

Demo finding the boiling point of water vs the boiling point of different concentrations of salt water or extend into a whole class practical whereby pupils measure the boiling point of different mixtures of salt water and compare.
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.
The three states of matter are: solid, , and gas.
Correct Answer: liquid, liquids
Q2.
Which of the following are examples of materials in the solid state at room temperature?
oxygen
fizzy drink
Correct answer: a building brick
milk
Correct answer: scissors
Q3.
All matter is made up of .
Correct Answer: particles, atoms
Q4.
Match the state of matter with the correct particle diagram.
An image in a quiz
Correct Answer:a,liquid

liquid

Correct Answer:b,solid

solid

Correct Answer:c,gas

gas

Q5.
Which description correctly describes a substance's melting point?
The temperature at which a liquid turns into a gas.
The temperature at which a liquid turns into a solid.
The temperature at which a gas turns into a liquid.
Correct answer: The temperature at which a solid turns into a liquid.
Q6.
What properties would you expect of a material with this particle arrangement?
An image in a quiz
can be compressed
Correct answer: cannot be compressed
Correct answer: can flow
particles only vibrate in fixed positions
cannot change shape

Exit quiz

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6 Questions

Q1.
A material is composed of only one type of chemical.
Correct Answer: pure
Q2.
Which of the following is an example of a pure substance?
sea water
Correct answer: iron
air
Q3.
What is the name given to a substance found in a material in very small amounts, but which can alter the material's properties?
Correct Answer: impurity, impurities
Q4.
Complete this sentence: A significant feature of a mixture is that it...
is composed of only two chemicals.
Correct answer: can be easily separated.
boils at a single, distinct temperature.
Q5.
Which diagram correctly represents a mixture in the solid state?
An image in a quiz
An image in a quiz
An image in a quiz
Correct Answer: An image in a quiz
An image in a quiz
Q6.
Which of these statements about mixtures are true?
Mixtures boil at a single, specific temperature.
Mixtures contain only three types of chemicals.
Correct answer: Mixtures boil over a range of temperatures.
Mixtures always include water.
Correct answer: Mixtures must contain at least two types of chemicals.