The snapper inside a cracker contains a small explosive charge which causes the noise when you pull on both ends of the cracker. How does this happen? The pulling forces create friction, and this friction releases heat energy. The heat generated is enough to ignite the tiny amount of gunpowder contained within the snapper, which you hear as a loud 'SNAP!'

	Make your own christmas crackers...
	You will need:
	Christmas ribbon. Christmas paper. Glue or sticky tape. Cardboard tubes, such as the rolls inside Christmas Paper or kitchen towel. You could also make your own from thin sheets of cardboard. For a jumbo cracker you can try making your own cardboard roll with a giant sheet of card. Snappers (you can buy these from craft shops). Things to put in your crackers eg Christmas hats, nuts, sweets, small toys, science jokes, pens, stickers, sample sachets, or science toys! Hint: don't pack sweets and highly scented objects in the same cracker. The sweets will probably absorb the scent, which will make them taste funny.
	Fill the tubes with goodies.
	Place a snapper through the tube so that the end hang out either side.
	Wrap each tube in paper, with some free paper on each end.
	Tape or glue the paper in place and then trim the ends so the paper is about 2cm longer on each side than the snapper ends.
	Tie the paper ends with several strands of curling ribbon. This will secure the contents from falling out.
	Decorate the outside. You're now ready to start snappin'!