Practical - Comparing Element, Compound and Mixture

Aims of the experiments:

1. To observe and compare the properties of compounds and mixtures made up of the same constituent elements.
2. Thus, infer some common characteristics of mixtures and compounds that can be used to distinguish them.

Part A: Investigating a mixture of elements

Place a spatula of iron filings and a spatula of sulfur powder on a piece of filter paper. Mix them together. Can the iron filings and sulfur be mixed in any proportion to form a mixture?

Observations: Iron filings were stuck onto the filter paper. The elements did not change colour. To form a mixture, the iron filings and sulfur can be mixed in any proportions.

Feel the mixture. Does it feel warm?

Observation: No

Move a magnet under the paper as shown in the diagram. Does the magnet separate the mixture of elements?

Observations. The iron filings are attracted to the magnet. The magnet separates the mixture of elements.

Add the iron and sulfur mixture into a test-tube of water. Stir the mixture and them let it stand for a while. Does water separate the mixture of elements?

Observation: Yes

Do the iron filings and the sulfur act as separate substances or a single substance with water?

Observation: Separate substances

Conclusions: The substance in a mixture can be mixed in any proportion. When a mixture is formed, heat and light are not usually taken in or given out. The mixture can be separated by physical means. The mixture has the properties of its constituent substances.

Part B: Mixture or Compound?

1. Mix one spatula of sulfur and half a spatula of iron filings in a crucible.
2. Cover the crucible with a lid and heat for 10 minutes using strong flame.

                                                                        Residue

The residue was not attracted by the magnet.

When put in water:

Residue did not separate into its components.

Conclusion: The reside formed is a compound. Iron and sulfur have gone through a chemical reaction to produce the residue - Iron (II) Sulfide. Although iron is magnetic, the residue was not attracted to the magnet, showing that it does not possess the properties pf its components. Moreover, the residue could not be separated by physical means (by water).