The Many Faces of Carbon

Why it matters

A sparkling diamond ring and the black lead in your pencil are made of the very same element — carbon! The same atoms, arranged differently, give wildly different materials.

Predict first

Diamond and graphite (pencil lead) are both made only of carbon atoms. Why is diamond hard while graphite is soft?

Diamond and graphite are different forms of the same element. The way the carbon atoms are joined gives diamond its hardness and graphite its slippery softness.

• They are made of different elements
• Their carbon atoms are arranged in different patterns — correct
• Diamond contains extra metal atoms
• Graphite is actually a compound

What you do

Arrange these four forms of carbon in order, from the hardest at the top to the softest at the bottom.

Check yourself

Diamond and graphite look totally different, yet chemists say they are closely related. Why?

Diamond, graphite, charcoal and soot are all different forms of the single element carbon. Same atoms, different arrangements — so their properties differ.

Which is the hardest natural substance known?

Diamond is the hardest natural substance on Earth. That is why it is used to cut glass and to tip drilling tools.

Which special property makes graphite useful in pencils and as an electrode?

Unlike diamond, graphite is soft and slippery, so it slides onto paper to leave a mark. It is also one of the few non-metals that conducts electricity, so it is used as an electrode.

• They are different forms of the same element, carbon — correct
• They are both compounds of carbon and oxygen
• They are mixtures that contain some carbon
• Graphite slowly turns into diamond in your pencil
• Diamond — correct
• Graphite
• Charcoal
• Iron
• It is slippery and conducts electricity — correct
• It is the hardest form of carbon
• It does not contain carbon
• It is a shiny yellow metal