Question

6. A mixture of pebbles, fine sand and salt was tinue sieved. What passed through the sieve wascmixed with water and allowed to stand. A sediment formed. The clear liquid was poured off and evaporated. The sediment also dried. Use a flow chart to show the procedure and what was collected.
​

Answer 1

A mixture of pebbles, fine sand and salt was sieved. During sieving, fine sand and sand passes out and pebbles remain because of their large size. So pebbles are separated.

Next, the mixture of sand and fine sand is mixed with water is allowed to stand. The sand settles down gradually as sediment under the effect of gravity. This process is called sedimentation. The clear water is then poured off into another container. This process is called decantation. So, after sedimentation and decantation, sand gets separated.

Now, the mixture consists of fine sand and water. This mixture is evaporated. Hence, the water evaporates and we get fine sand.

(See the image for the flowchart. I suggest you make your own flowchart.)

Answer 2

The aggregate should be oven-dried at high temperature before sieving to prevent lump formation of the fine particles due to moisture content, which might clog the fine sieve holes.