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Lesson · Grade 7 · Science

Pure substances and mixtures

  • Grade 7
  • Science
  • 1 min 10 s
  • British Columbia
  • BC7-SC-13

Zooming in on copper, water and air shows that copper (an element) and water (a compound) each have only one kind of particle, so both are pure substances. Air is mostly nitrogen and oxygen particles, mixed together but not joined, so it is a mixture.

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In one sentence

The question this lesson answers

Copper, water and air. Is each one a pure substance or a mixture?

Let us zoom in on a piece of copper.

Transcript

What the lesson says

Copper, water and air. Is each one a pure substance or a mixture?

Let us zoom in on a piece of copper.

Every particle in it is the same, a copper atom.

A substance with only one kind of atom is an element.

Now let us zoom in on a drop of pure water.

Every particle is the same, one oxygen atom joined to two hydrogen atoms.

Different kinds of atoms joined together make water a compound.

Copper and water each have only one kind of particle, so both are pure substances.

Now let us zoom in on a jar of air.

Air is mostly nitrogen and oxygen, two different substances.

Their particles are mixed together, but they are not joined to each other.

Two or more substances, mixed but not joined, make a mixture.

So elements and compounds are pure substances, and a mixture has two or more substances in it.

Curriculum

Where this fits

British Columbia, Grade 7

Science, Chemistry: elements and compounds are pure substancesBC7-SC-13

Previous: Compounds: Different Atoms Joined TogetherNext: Density: why some things float

The outcomes and strands follow the British Columbia curriculum.

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