MediumChemistryHigh School (9–10)GeneralMixtures and Solutions › Elements, Compounds and ChangesConceptual
Iron filings and sulphur powder are mixed in a dish.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Iron filings and sulphur powder are mixed in a dish. The same amounts are then heated strongly together in a test tube, and a dark grey solid forms.
- What happens when a magnet is brought near each?
- Sulphur dissolves in a liquid called carbon disulphide. What happens when each is stirred into it?
- Which one is a compound?
Need a reminder? The key ideaShow
A compound is two or more elements joined chemically in a fixed ratio by mass, with new properties, split only by a chemical change. Water is hydrogen and oxygen in the ratio ; iron sulphide is iron and sulphur in the ratio . A mixture can have any ratio.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The magnet pulls the iron out of the mixture. It does not pull the dark solid, because the iron in it is joined to sulphur.
Step 2. (b) The sulphur in the mixture dissolves and leaves the iron behind. The dark solid does not dissolve, because it holds no free sulphur.
Step 3. (c) The dark solid, iron sulphide, is the compound: it has new properties, and its iron and sulphur cannot be separated by simple means.
Answer: (a) Only the mixture's iron is pulled. (b) Only the mixture's sulphur dissolves. (c) The heated solid is the compound.
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