The Mystery Powder Test
- Chemistry
- Ages 8–11 · Grades 3–5
- Hands-on experiment
What you’ll find out
- Every material has properties that can be observed and measured.
- Several tests together can identify a material, even when things look alike.
- A fair test changes only one thing at a time.
No sign-up and no real names. In the lesson you check your understanding as you read, run the experiment yourself, and practise until it sticks.
Four white powders
Salt, sugar, baking soda and cornflour are all white powders. In a dish they look almost the same. Chemists tell them apart by their properties. A property is something you can see or measure. Under a magnifying glass, salt grains look like tiny cubes. Sugar grains look like bits of glass. Baking soda and cornflour look like fine dust. Stir them into water. Salt and sugar disappear, and so does most of the baking soda. Cornflour makes the water cloudy, then sinks. Each test gives a clue. You must never taste a powder to find out what it is.
Tests that react
Some tests use reactions. Drip vinegar on each powder. Baking soda fizzes, making bubbles of a gas called carbon dioxide. The others do nothing much. Now drip on iodine, a brown liquid. Cornflour turns dark blue-black, because it contains starch. The others do not. Scientists write the results in a table. Each powder has its own pattern of results, like a fingerprint. To name a mystery powder, do the same tests and find the pattern that matches. Use the same amount of powder and drops each time, to keep it fair.
Curriculum links: NGSS 5-PS1-3