Colourful chemistry

Loads of important scientific skills are utilised in these experiments, ready to entertain and inform learners.

Skill development

Children will develop their working scientifically skills by:

• Drawing conclusions and raising further questions that could be investigated, based on their data and observations.
• Asking their own questions about scientific phenomena.

Learning objectives

• Compare and group everyday materials on the basis of their properties.

Rainbow Density Column

Equipment

• A tall, clear container - a fizzy drink bottle is ideal
• Honey
• Glucose syrup
• Maple syrup
• Whole milk
• Washing up liquid

Procedure

1. Measure out the same amount of each liquid, so your rainbow layers will be equal sizes.
2. Pour the liquids into a tall, clear container very slowly in the following order, making sure they DON’T touch the sides of the glass first: honey, glucose syrup, maple syrup, whole milk, and washing up liquid (the runny kind). The slower you pour, the better the column will look.
3. Next pour the rest of the liquids in the following order, making sure they DO touch the side of the glass first: water, vegetable oil, rubbing alcohol (surgical spirit), lamp oil. Again, pour as slowly as you can.

What’s the chemistry?

Liquids have many different densities - so a cupful of one liquid can be heavier than a cupful of another liquid. If you pour liquids with different densities slowly into a tall container, you can see them separate out in order of density.

Homemade lava lamp

Equipment

• A tall, clear containing - a fizzy drink bottle is ideal
• Food colouring
• Alka-Seltzer tablets
• Water
• Vegetable oil

Procedure

1. Fill a tall, clear container ¾ full, with the vegetable oil.
2. Fill the rest up with water, almost to the top, but leave a couple of fingers-widths clear.
3. Add about 10 drops of food colouring. Which liquid does the food colouring dye? Can you think why that might be?
4. Drop in a small piece of an Alka-Seltzer tablet, and watch what happens.

What’s the chemistry?

Not all liquids will mix with each other and however hard you try, the oil and water will never mix into one layer. Adding in a fizzing Alka-Seltzer gives the water enough energy to bubble past the oil.

Concepts supported

Children will learn that:

• Different liquids have different densities.
• The properties of different liquids affect whether a substance will dissolve and form a solution.

Suggested activity use

This resource can be used as a discussion tool with small groups, based around predictions and observations, as various liquids are added to the density column. This will allow you to make assessments based on children’s responses.

Alternatively, the activity could be set up to allow a whole class to carry out the experiment, working in small groups. Children can follow your prompts, again allowing them to note observations and offer explanations as to what is happening. This could provide a platform for studying densities or dissolving properties of different liquids.

This activity also links well with K-Mistry’s Dense liquids: kitchen science podcast.

Practical considerations

You will need to provide equipment, and various liquids of different densities, in order to carry out the experiment.

Children may need some help when creating the rainbow density columns.

Please take into account any health and safety considerations, particularly with regard to the use of Alka-Seltzer tablets.