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Lesson · Grade 7 · Science

Compounds: Different Atoms Joined Together

  • Grade 7
  • Science
  • 1 min 5 s
  • British Columbia
  • BC7-SC-12

Zooming into a drop of water and a grain of salt shows that water is one oxygen atom joined to two hydrogen atoms, and salt is sodium and chlorine joined one for one in a repeating pattern. Both are labelled as compounds and then bracketed together as pure substances, ending on the recap that a compound is different atoms joined together.

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In one sentence

The question this lesson answers

Water and salt are both compounds. But what is a compound?

Let us zoom in on a drop of pure water.

Transcript

What the lesson says

Water and salt are both compounds. But what is a compound?

Let us zoom in on a drop of pure water.

Water is made of two different kinds of atoms, oxygen and hydrogen.

Each water molecule is one oxygen atom joined to two hydrogen atoms.

A substance made of different atoms joined together is called a compound.

Now let us zoom in on a grain of table salt.

Salt is made of two different elements, sodium and chlorine.

They are joined in a repeating pattern, with one sodium for every chlorine.

So salt is a compound too.

Sodium, a shiny metal, and chlorine, a poisonous gas, join to make the salt we eat.

Every bit of pure water or pure salt is the same, so compounds are pure substances.

So a compound is a pure substance made of different atoms joined together.

Curriculum

Where this fits

British Columbia, Grade 7

Science, Chemistry: elements and compounds are pure substancesBC7-SC-12

Previous: Finding an element on the periodic tableNext: Pure substances and mixtures

The outcomes and strands follow the British Columbia curriculum.

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