Colour Changing Christmas TreeCreate a Christmas tree centrepiece that changes from plain white to red and green before your

eyes, using pantry ingredients for some kitchen chemistry.

You’ll need A few red cabbage leaves

A blender/mixer

A kitchen strainer

45 x white pipe cleaners

15 x small white pom poms

Citric acid

Bicarbonate soda

A spoon

A kettle

Two containers that can hold about 250ml of hot liquid

Two trays or plates

Water

A small foam cone, about 10cm tall

A toothpick

A mister/spray bottle

Safety considerationsThis activity should be done under adult supervision, due to the use of:

a) hot tap water and a kettle

b) an electric blender/mixer

c) scissors to cut pipe cleaners into 1.5 cm pieces and

d) a potential choking hazard for very young children with small pieces of pipe cleaner and pom poms.

Environmental considerationsIf you do not wish to use a foam/Styrofoam cone, try making a cone from recycled cardboard and poking holes into the cardboard to insert the pipe cleaners. You can also reuse the foam cone from year to year, by removing the pipe cleaners and pom poms for disposal.

Starting off Preparing the Christmas tree You need to soak and dry the pipe cleaners and pom poms, so do this overnight or several hours ahead of time (or overnight).

1. Cut the pipe cleaners into 2.5cm lengths.

2. Boil 2 cups (500mL) of water in the kettle.

3. Pour 1 cup of the boiled water into a container. Add bicarbonate soda to the hot water, one spoon at a time while stirring. Stop adding bicarbonate soda when no more will dissolve in the water. You now have a saturated solution of bicarbonate soda.

4. Soak the pipe cleaner pieces in the saturated solution of bicarbonate soda. Stir around for 30 seconds and then carefully remove the pipe cleaner pieces. You might want to use a slotted spoon or tongs to avoid the hot water in the solution.

5. Pat dry the pipe cleaners with a paper towel. Lay the pipe cleaners in a single layer on a tray or plate and place in the sun to dry.

6. In a different container, pour ½ cup of boiled water. Slowly add 75g of citric acid to the hot water, stirring to ensure it all dissolves.

7. Soak the pom poms in the citric acid solution. Stir around for 30 seconds and then carefully remove the pom poms. You might want to use a slotted spoon or tongs to avoid the hot water in the solution.

8. Pat dry the pom poms with a paper towel. Lay the pom poms in a single layer on a tray or plate and place in the sun to dry.

9. Once the pipe cleaners and pom poms are dry, you are ready to make your Christmas tree!

Making the Christmas tree1. Pre-poke holes around the small foam or cardboard cone using a wooden toothpick or

skewer.

2. Insert pipe cleaner pieces into the holes to create the branches of the tree. Once you have poked enough pipe cleaner pieces in to fill-in the entire cone, you may want to bend and shape them gently to make it look more “tree-like”.

3. To finish decorating the tree, gently wedge some pom poms between pipe cleaner branches.

Red cabbage indicator1. Pour about 500mL of hot water (from the tap) into the blender.

2. Add three large red cabbage leaves to the blender.

3. Place the lid on the blender and blend until smooth.

4. Pour the mixture from the blender through a strainer to take out any solid pieces of cabbage.

5. You can add the red cabbage indicator liquid straight to the spray/mister bottle, or keep it in another sealable bottle. Store in the refrigerator for up to 3 days.

Revealing your Christmas colour1. Before spraying the tree, you should be aware that the red cabbage indicator can stain.

Place the tree on a wide plate or tray and line the table with newspaper to collect drips of indicator (or take the tree outside).

2. Pour the red cabbage indicator solution into the spray/mister bottle.

3. Spray the red cabbage indicator evenly onto your Christmas tree. The more you spray, the more colour you will reveal! It’s best to spray the tree, then let it dry slightly before spraying it again many times over.

4. An alternative method is to very quickly dip the tree into a jug filled with red cabbage indicator. This gives a more immediate result, but it also contaminates the indicator, so you cannot use it for other Christmas trees.

What’s happening?A pH indicator is something that is used to help determine a substance’s pH, using colour changes to indicate pH level. The pH of a substance is its level of acidity or alkalinity. To be more precise, pH is a measure of the concentration of hydrogen ions (H+) relative to hydroxide ions (OH-) in a substance. More acidic substances, like lemon juice and vinegar have a low pH, and more alkaline substances like sodium bicarbonate have a high pH.

pH indicators, like the red-cabbage indicator, contain colour pigments that change colour depending on the pH. At a neutral pH, the cabbage indicator is purple-blue, but turns red at low pH or in the presence of an acid and green at a high pH or in the presence of a base. When the indicator touches the areas of the Christmas tree that are acidic or alkaline, it changes colour accordingly.

Lots of coloured plants contain pigments that react to pH. The pigment we extracted from cabbage, anthocyanin, is also found in berries, tree leaves, and flowers. Flowers like hydrangeas are very sensitive to changes in pH and will actually grow different colours depending on the pH of the soil.

There are many different indicators around available to test – maybe you’ve seen similar in water testing kits. Another indicator you could try using at home is turmeric. It only has one colour change, from yellow to red in alkaline solutions.