What it shows
Blood is made of a pale yellow liquid, plasma, with red cells, white cells and platelets floating in it. A sealed bottle with beads shows the parts and their rough amounts.
The science
Plasma is about 55 percent of blood and is mostly water, carrying dissolved food, hormones and waste. Red blood cells, about 44 percent, carry oxygen using haemoglobin and have no nucleus. White blood cells are few but fight germs, and platelets are tiny fragments that help blood clot at a cut. A bottle model shows that red cells are by far the most numerous, white cells rare and platelets small.
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.
- A small clear plastic bottle with a cap
- Water with a few drops of yellow food colour
- About 100 red plastic beads or red sequins
- A few (3 to 5) larger white beads
- A teaspoon of tiny glitter or rice grains as platelets
- A label sheet with a legend
- Waterproof glue to seal the cap
- A funnel
Safety
For this project: Beads and sequins are small parts, so keep them away from young children. An adult must apply the glue to the cap and supervise.
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
8 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.
Fill the bottle with yellow-tinted water to about three quarters full to show the straw-coloured plasma.
Use the funnel to add about 100 red beads, which stand for the red cells, because they are the main solid part of blood.
Add only 3 to 5 large white beads to represent the white cells, which are much rarer and larger.
Add a small pinch of glitter or rice for the platelets, which are tiny.
Put the cap on, glue it for safety and shake the bottle gently to mix everything.
Make a key on a card: red beads equal red cells and oxygen carriers, white beads equal germ fighters, glitter equals clotting helpers and yellow liquid equals plasma.
Add a label showing the approximate percentages: plasma 55, red cells 44, white cells and platelets less than 1.
Draw a flow arrow on the card showing blood travelling from the heart to the lungs and the body.
What you should see
The bottle shows a yellow liquid with many red beads, few white beads and a few glitter specks, and the key explains the job of each part.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What is the liquid part of blood called?
Plasma.
2Which cells carry oxygen?
Red blood cells, using haemoglobin.
3What do white blood cells do?
They fight germs.
4What do platelets do?
They help blood clot at a cut.
Take it further
Make a bigger jar model with exact bead numbers for the proportion of red cells to white cells, which is around 600 to 1.
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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