# How Dangerous is Your Christmas – 3. Decorations

Scientists Dave Porter and Fran Scott show Dick and Dom some festive science experiments. If you would like to try them yourself, here’s how!

Symmetrical snowflakes, sugary treats and a scientific way to put out Christmas candles.

## Activity 1: Symmetry

Something is symmetrical when one side looks the same as the other. If you place a mirror on a line of symmetry, you should see an exact copy of the original shape. You can explore symmetry while making some Christmassy decorations. Start with Christmas trees. Fold a piece of A4 paper in half. Then, taking the fold as the middle, draw one side of a tree, and cut out your shape. When you unfold your paper, you should have a whole tree – with both halves exactly the same. Can you draw baubles on it symmetrically as well?

You can also make snowflake-like designs. For this you need a square piece of paper. Fold it in half, and then in half again. And then fold it in half again, this time so it makes a triangle shape. Then, take some scissors, and cut out shapes in your folded paper. What do you get when you unfold it? Can you see the symmetry?

The snowflakes Fran makes in the programme have four sides. But real snowflakes have six. You can make a six sided snowflake by folding your square piece of paper in half so it becomes a triangle, and then in half again. Then, you need fold it into thirds – folding it over itself to make shape like an arrowhead. Then, cut the top off to give you a triangle shape. Cut patterns out of your triangle, and unfold!

## Activity 2: Edible crystals

How to make some pretty sugar crystals that are both decorative and edible.

You will need:

• A small pan of hot water
• Sugar
• Jam jar
• String or baking twine
• Food colouring (optional)

Tie your string around a knife or pencil, and place it across the top of the jam jar. You want the string to dangle so that it doesn’t touch the bottom or the sides.

Heat up the water in a pan. Then add some sugar - about the same amount of sugar as water. Stir it until it dissolves. Keep stirring so that the sugar doesn’t stick to the pan. Take care because the pan will be very hot. When all the sugar has dissolved, add some more, and stir until that too has dissolved. Repeat the process until no more sugar will dissolve in the water. Now, if you want to create coloured crystals, add a few drops of food colouring. Then, take the pot off the heat and allow it to cool down slightly.

Remove the string from the jam jar, and ask an adult to pour the solution into the jar. Be very careful – the liquid will be extremely hot. Then, put the string, still tied to the knife, back onto the jar. Cover the top with a paper towel and leave it somewhere safe. After a few days, sugar crystals should grow along the string.

What’s happening

By dissolving sugar in the water you are creating a solution. A solution which can hold no more of a substance, in this case sugar, is called a saturated solution. When a solution is saturated, anything more added will not dissolve. However, the amount you can dissolve depends on temperature. In this activity, because the water you are using is hot, you can dissolve even more sugar in it – you are actually making a supersaturated solution. As the water cools down, and then as time goes on, evaporates, it can no longer hold all the sugar. The sugar comes out of solution and forms crystals – hopefully on your string!

## Activity 3: A fire extinguisher for Christmas candles

This experiment needs a lit candle, so adult supervision is required.

There are often lots of candles around the house at Christmastime – but how about using science to put them out? You need some vinegar, some bicarbonate of soda, a 2 litre jug, and a lit candle.

Measure out 100ml of vinegar into your jug. Then, quickly, add 3 teaspoons of bicarbonate of soda. They will react together, creating carbon dioxide gas – that’s what’s making it foam up. When the bubbles start to pop and the foam dies down, try pouring the gas over the candle – not the liquid inside the jug, but the gas that your reaction has created. Although it looks like you’re not pouring anything at all, your candle should go out!

What’s happening

Flames need oxygen from the air to burn. Carbon dioxide is heavier than air, so it “pushes” the oxygen out of the way around the candle, and the flame goes out. Early fire extinguishers worked in exactly this way - they contained bicarbonate liquid and a glass capsule of sulphuric acid!