Chemistry in your shopping basket

This experiment should take around 60 minutes.

Skill development

Learners will develop their working scientifically skills by:

• Asking their own questions about scientific phenomena.
• Using appropriate scientific language and ideas to explain, evaluate and communicate their findings.

Learning objectives

• Compare and group materials together, according to whether they are solids, liquids or gases.
• Observe that some materials change state when they are heated or cooled, and measure or research the temperature at which this happens in degrees Celsius.
• Demonstrate that dissolving, mixing and changes of state are reversible changes.
• Explain that some changes result in the formation of new materials, and that this kind of change is not usually reversible.

Concepts supported

Children will learn:

• That chemistry plays many important roles in our day to day lives.

Suggested activity use

These activities can be done as a whole class carousel of activities to demonstrate that chemistry is everywhere, including in items you may buy at the supermarket. A number of adults may be required to supervise the various tasks.

These activities would be suitable to be used as part of a science week, or just individual activities picked to stimulate discussion and questioning at the start of a relevant topic.

Health, safety and technical notes

• Read our standard health and safety guidance here
• Safety goggles, lab coats, and gloves should be used for all experiments.

Sodium Chloride

Equipment

• Margarine
• Toilet paper
• Soap
• Bleach
• Table salt
• Small clear plastic bag and twist-tie
• Large clear plastic bag and twist-tie
• Plastic washing up bowl
• Bag of ice x 2
• Cup of milk
• Vanilla essence
• Sugar, 1 tablespoon

Procedure

1. Pour the milk into the medium sized clear plastic bag and add the sugar and a few drops of vanilla essence. Seal the bag.
2. Empty the ice into the large clear plastic bag and add two large tablespoons of salt. 
3. Place the smaller bag containing the milk into the larger bag and shake the mixture. This is best done in the plastic washing tub to avoid spillage. 
4. Ask the volunteers to continue shaking the mixture for 20 minutes.
5. Continue with the following activities and towards the end of the session invite pupils to try their homemade ice cream

Carbon Dioxide

Equipment

• Bread
• Cake
• Bottle of fizzy pop
• Decaffeinated coffee
• Balloons x 3
• Dry Ice
• Powder funnel
• Hot water
• Flask, 1 L
• Universal indicator

Procedure

1. Add several pellets of dry ice into a couple of non-inflated balloons (Tip: blow into the neck of the balloon to “free” it first and use a powder funnel placed in the neck of the balloon to aid getting the pellets in!). Tie knots to seal each balloon.
2. Pass the balloons round the room, asking the pupils to pass them from hand to hand. The balloon will inflate as the dry ice sublimes.
3. Once the balloons have fully inflated with carbon dioxide, blow up a balloon with air and compare the rates at which the two fall to the floor. Explain how the balloon filled with carbon dioxide drops faster because it is more dense than air.

Crude oil

Equipment

• Candle
• Fleece
• Fairy liquid, at least 40 ml
• Lipstick
• Plastic washing up tub
• Measuring cylinder, 250 ml 
• Hydrogen peroxide 30%, 30 ml 
• Manganese dioxide powder (NOT granules)
• Blue food colouring

Procedure

1. Place the measuring cylinder in the middle of the plastic washing tub.
2. Add around 40 ml of detergent to the cylinder. Add a few drops of blue food colouring to make the toothpaste colour.
3. Add a small amount (no more than half a level spatula) of manganese dioxide powder and mix well.
4. Measure approx. 30 ml of 30% hydrogen peroxide into a plastic cup and then quickly pour into the cylinder - stand well back as the reaction will take place very quickly! Hot coloured foam will shoot out of the cylinder.
5. Once the foam has cooled, clean up with water.

Nitrogen

Equipment

• Polystyrene cup
• Frozen peas
• Crisps
• Light bulb
• Liquid nitrogen
• Banana
• Piece of wood
• Nail (large-headed – roof felt tacks work well)
• Gloves
• Piece of rubber tubing

Procedure

Discuss the properties of liquid nitrogen and how its very low temperature freezes items rapidly. At these extreme cold temperatures (-196°C) the properties of materials are significantly different. The workshop provider will then prove a banana can hammer a nail into a piece of wood using liquid nitrogen and/or that a piece of rubber tubing becomes hard and brittle. 

Ultraviolet

Equipment

• Sunscreen
• £5 note/ credit card T
• Tin of white paint
• Washing powder
• UV lamp
• Bottle of tonic water

Procedure

1. Give a brief introduction to the electromagnetic spectrum and explain where the visible and UV ranges sit. Pupils will be aware of the effects of UV through sunburn and understand that UV is found in sunlight.
2. Use the lamp to demonstrate how white clothes phosphoresce under UV radiation and link this back to the washing powder.
3. Then show the tonic water glowing blue under UV. Explain that green peas and beans glow red, whilst ripe bananas glow blue. These properties are used by food processors when selecting produce.
4. The watermarks on the £5 note and the invisible MC marking on the credit card are used to demonstrate the effects of UV. Using a UV lamp, show the pupils the ‘invisible’ markings.

Practical considerations

Extra adults will be required to help supervise the activities if running them as a carousel.

Primary schools may find it difficult to get hold of some of the chemicals required for some of the activities.

When using this activity, it is possible to introduce or reinforce the misconception that the formation of ice cream is a reversible change. In fact this isn’t true. The formation of the substance called ice cream from its original ingredients is a chemical change, and hence is irreversible. Once formed, the substance is frozen, allowed to melt to a liquid form, and then frozen back to a solid again, so this process could be argued as being a reversible change of state – solid to liquid to solid.