What it shows
Different stains need different cleaners: tea stains respond to mild acids and detergents, while turmeric responds to sunlight and detergent. You test cleaning liquids on identical stains and score the result.
The science
A stain is a coloured substance sticking to the fibres of the cloth. Detergent molecules surround the particles and lift them into the water. Mild acids such as lemon juice can change tea pigments so they lose colour, and turmeric dye fades in sunlight because light breaks the colour molecule apart.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- Old white cotton cloth cut into 12 squares
- Turmeric paste and strong tea
- Detergent solution, lemon juice, vinegar, plain water
- Small bowls and a spoon
- Rubber gloves
- A clock and a clothesline
- A marker for labelling squares
Safety
For this project: Wear gloves because detergent can irritate skin, and do not mix any two cleaners together. An adult must supervise, and keep the liquids away from the face.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
7 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Make six squares of cotton with turmeric stains and six with tea stains, each of the same size and strength.
Let all stains dry for an hour so they set.
Soak one turmeric and one tea square in each liquid: detergent, lemon juice, vinegar, plain water, and keep two more as controls.
Leave them for twenty minutes, then rub gently with the fingers for one minute.
Rinse each square in clean water and hang them in the same place to dry.
Put one of the controls in direct sun for two hours to see the effect of sunlight.
Score each cloth from 0 for no change to 5 for gone and compare them in a table.
What you should see
Detergent clears tea well, lemon juice helps a little with both and plain water does least. The turmeric square left in the sun fades most, showing that light removes that dye.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1How does detergent remove dirt?
Its molecules lift particles off the fibre and into the water.
2Why is a control used?
To compare with doing nothing special.
3Why does turmeric fade in the sun?
Light breaks up the dye molecules.
4Why must cleaners never be mixed?
Some mixtures give harmful gases.
Take it further
Repeat with ink, curry oil and chocolate stains, and make a stain removal guide for your family.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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