Carbon Clash

Carbon Clash: why diamond and graphite are so different when both are pure carbon

This free game is part of our AQA GCSE Chemistry (8462) course for exams in EXAM YEARS 2027-2029.

Diamond: four covalent bonds in a giant covalent structure

For AQA GCSE Chemistry (spec point 4.2.3.1), in diamond each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure. A carbon atom has four electrons in its outer shell, so it can form four covalent bonds, and in diamond it uses all four. The bonds point out in three dimensions, so every atom is locked in place by four strong bonds and the pattern repeats in every direction. That is why diamond is very hard, has a very high melting point and does not conduct electricity.

In Carbon Clash you build the diamond yourself. Each carbon atom shows its open bonds as glowing stubs pointing out in 3D. Tap one and the carbon gun fires a new atom at it, which bonds to every neighbour it reaches. When an atom has all four bonds a green 4 pops up. Then the drill test: hold the drill on your crystal and watch the sparks fly and the steel bit go blunt without leaving a scratch, because the drill would have to break many strong covalent bonds. Clip on a circuit and the bulb stays dark: all four outer electrons of each carbon are used in bonds, so there are no delocalised electrons and no ions to carry the charge.

Graphite: three bonds, layers of hexagonal rings and delocalised electrons

Spec point 4.2.3.2 says that in graphite each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings which have no covalent bonds between the layers, and that one electron from each carbon atom is delocalised. In the game the open bonds lie flat, so your build grows into a flat sheet of six-sided rings, and you see the fourth outer electron of every new atom pop off and join a moving swarm of delocalised electrons. The stacker then drops more layers on top, held only by weak forces.

Drag sideways across the stack and the layers slide over each other, which is why graphite is soft and slippery and used in pencils and as a lubricant. Switch on the circuit and the bulb lights as the delocalised electrons drift from the negative clip towards the positive clip: graphite conducts electricity, and in that way it is similar to metals. Finally, both carbons go into an argon furnace next to a block of iron. The iron melts at 1538 °C, but diamond and graphite are still solid at 3000 °C, because to melt a giant covalent structure many strong covalent bonds must be broken. Graphite is soft, but the bonds inside its layers are strong.

Common mistakes the game picks up

Graphite is not soft because its covalent bonds are weak: the bonds inside the layers are strong, and it is soft because there are no covalent bonds between the layers. Graphite does not have a low melting point. Diamond has no intermolecular forces, because it is not made of molecules; write many strong covalent bonds instead. Graphite has no ions: it conducts because of delocalised electrons, and the current is those electrons moving, not electricity slipping through the gaps between layers. Every wrong call in the game opens a short explanation with a link back to the lesson.

How to play Carbon Clash

Tap a glowing open bond to fire a carbon atom at it, or press Space or the FIRE button to shoot at the highlighted one (the arrow keys pick another). Then run the tests: hold DRILL, drag sideways to SLIDE, press SWITCH ON, and hold HEAT. Some tests ask you to call the result first. There are five levels: Diamond, Graphite, Orders (set the carbon gun to 4 BONDS or 3 BONDS for drill tips, pencil leads, lubricant, electrodes or saw teeth, then prove it with the right test), Spot it (call 3D models and exam-style diagrams diamond or graphite by counting the bonds on one atom) and a 70 second Carbon Rush. It works with a mouse, touch or keyboard, and takes about 7 to 9 minutes.

Exam tip: always start with the structure (how many bonds each carbon atom makes and the shape), then link it to the property with “so” or “because”. For conduction, the mark is for saying the electrons are delocalised.