In a classroom demonstration, a chemistry teacher presented a mixture of three substances : iron filings (component A), common salt (component B) and sulphur powder (component C) in order to teach students about the separation of mixtures. He then asked the students to observe the steps carefully :

• When a magnet was brought near the mixture, one of the components was quickly separated.
• Water was then added to the remaining mixture. One of the substances dissolved, while the other did not.
• The insoluble component from the solution was separated through filtration.

Answer the following questions :

(a) What kind of solid-solid mixture was brought by the teacher ? Justify your answer.

(b) What was the observation when a magnet was brought near the mixture ? Why ?

(c) Which component remained insoluble and was collected on the filter paper ? Name the term used for the substance left on the filter paper.

(d) Can the component that dissolved in water be recovered from its solution ? How ?

(e) Give two examples of mixtures which you use in your daily life.

(a) The teacher brought a heterogeneous solid-solid mixture because its components — iron filings, common salt and sulphur — are different substances and can be separated by physical methods.

(b) Iron filings (Component A) get attracted to the magnet and are separated because iron is a magnetic substance, while salt and sulphur are non-magnetic.

(c) Sulphur (Component C) remains insoluble in water and is collected on the filter paper. The substance left on the filter paper is called the residue.

(d) Yes, the component that dissolved in water can be recovered from its solution. The dissolved substance is common salt (component B). It can be obtained by evaporating the water. When water evaporates, common salt is left behind as solid crystals.

(e) Two examples of mixtures used in daily life are:

1. Salt and water
2. Tea