Yummy Science – Honeycomb Toffee . Experiments you can try in the kitchen – Custard Bouncing Balls, Magical Water, Growing Crystals, Spud Guns, Designer Onions, Self Slicing Banana, Sticky Milk, Toast Busters, Toasty Science, Secret Messages

Science Links

More fun nutrition activities at
the Rowett Research Institute, eduweb
Check out National Science & Engineering Week at:
The BA (British Association for the Advancement of Science)

Further food science ideas for the primary aged audience are presented in the ‘Food for Thought resource, downloadable at The BA

For secondary pupils, there are lots of great kitchen chemistry ideas available in the Salters Chemistry Club handbooks or in various publications produced by the Royal Society of Chemistry

Exploring the science:

Bicarbonate of soda is used in cooking to help a mixture rise by adding carbon dioxide. In this recipe it is the heat that causes the bicarbonate of soda to break down releasing carbon dioxide in the process.

Taking it further:

Reaction of bicarbonate of soda with an acidic liquid also causes carbon dioxide to be released. To make a fizzy drink to wash your toffee down with, try taking a glass of fruit juice such as orange juice (which contains citric acid and ascorbic acid), and add a teaspoon of bicarbonate of soda.
Can you think up a better name for honeycomb toffee?!

Safety: Adult supervision is recommended when making toffee as boiling sugar can cause scalding.

Indulge in a bit of kitchen chemistry and make yourself some of this delicious toffee also called cinder toffee, hokey pokey and sea foam in different parts of the world.

You'll need:

100 g sugar
2 tablespoons of syrup
Large, heavy based saucepan
1 heaped teaspoon of Bicarbonate of soda
Tin lined with aluminium foil (to save on washing up!)

N.B. There are LOTS of different recipes for making honeycomb toffee but this is one of the simplest.

What to do:

Mix the sugar and syrup together with a wooden spoon in the saucepan. Place on the stove on low heat until the sugar is melted i.e. if you drag a wooden spoon over the saucepan base it no longer feels 'gritty' - this may take 10-15 minutes.
Swirl the bubbling contents of the pan around from time to time but constant stirring isn't necessary. Once the sugar is all melted, take the pan off the heat, add the bicarbonate of soda, stir to mix and watch the mixture froth up.
Pour the mixture into a tin lined with foil and then put the saucepan IMMEDIATELY into soak (take care, saucepan is hot). Leave toffee to cool then break into chunks and enjoy!

What happens:

The bicarbonate of soda breaks down with heat to release carbon dioxide gas. The gas causes the toffee mixture to froth and the gas becomes trapped in the sugar/syrup mixture.