LEARNING / AT HOME

Acid rain Whip up a batch of your own acid rain to help teach your child about the effects of this damaging pollutant

Acid rain is caused when harmful gases dissolve in the water in the atmosphere. The most common culprits are nitrogen oxide and sulphur dioxide, both of which are found in car exhaust fumes. These dissolved gases cause the pH of the water in the atmosphere to drop, leading to rain that is more acidic than usual (normal rain water is slightly acidic). This acid rain can cause physical damage to the planet by weathering (breaking down) rocks and by causing ponds and lakes to become more acidic, harming wildlife. In this investigation, your children make their own "acid rain" and explore it's effects.

What you need: Some water and some white wine vinegar or lemon juice. In order to test the effects of your acid rain you will need an eyedropper or pipette and some substances to "rain on".

To make the rain, have your child add a tablespoon of the white wine vinegar or lemon juice to a mug of water. If you want to test how acidic your rain is you can use strips of universal indicator paper, which can be purchased from gardening centres. Acid rain is typically around pH 5.5. Once your child has made their acid rain, they can then test its effects by adding drops to the different substances they are testing. A comparative test could be made by also using tap water to see the difference in the effects. Testing a selection of rocks from the garden will help children to see the impacts of chemical weathering, a big factor in the breakdown of certain rocks. You could also use a stick of chalk and some clay, which are both examples of sedimentary rock. Have your child carefully examine the material they are testing, including its appearance and texture, before they add the acid rain. They could even weigh the material they are testing to see if any of the material is ‘lost’ when it comes into contact with the acid rain. When the acid rain has been added your child can observe what they see and hear and then compare the material to how it looked, felt and weighed before the acid rain was used.

=

'Acid rain can cause physical damage to the planet by weathering rocks'

=

Natural dyes Explore how to make natural dyes by making your own tie-dyed t-shirt

Dyes have been used for centuries in order to colour cloth. In the past, most dyes came from natural sources such as plants and vegetables. Although some natural dyes are still in use, synthetic dyes are increasingly being utilised in manufacturing. Synthetic dyes are often valued by manufactures for the consistency and vibrancy of the colours they produce. The downside, however, is that many synthetic dyes can have an adverse effect on the environment. Natural dyes, on the other hand, are extracted from plants and as such produce no harmful waste and do not require large amounts of energy to produce.

What you need: To make your natural dye you will need to collect some natural materials with strong pigments. Good choices are red cabbage or beetroot for purple, turmeric and courgette flowers for yellow, coffee grinds or used tea bags for brown, blackberries and red onion for pink and spinach can be used to make a shade of green. In addition to your natural materials you will also need; a large saucepan, some white wine vinegar and some elastic bands. To make your dye, have your child fill the saucepan with cold water and add the first natural material you have chosen. For plant materials it is best roughly chop or tear them up so that as much of the dye as possible can be released. Bring the water to a simmer and leave for an hour. You should then find that the dye has been released and you have a pan full of coloured water. Allow the water to cool before moving onto the next step.

To make a tie-dyed t-shirt you will need a clean, dry cotton t-shirt. Your child should roll the t-shirt up into a long sausage shape, then twist the t-shirt tightly in a few different places and add an elastic band to hold the material in place. You then need to add a fixer. Natural dyes are not as colourfast as synthetic dyes, as there are no added chemicals that ‘hold’ the dye onto the fabric. However, a natural fixer can be used instead, in this case white wine vinegar. Add a tablespoon of white wine vinegar to a new pan of water and bring to the boil. Add the t-shirt, reduce to a simmer and leave for one hour. When the hour is up, remove the t-shirt, rinse in cold water (do not dry) then add the t-shirt to your pan of coloured water. Simmer the t-shirt in the coloured water for one hour then remove the t-shirt, rinse in cold water, and allow to dry. The t-shirt is now ready to wear.

40

AUGUST/SEPTEMBER 2015 www.thegreenparent.co.uk