The mass of an unidentified rock is 40 grams. Students determine the volume of the rock by placing the rock in a cylinder with water. The students calculate the density of the rock. They determine the identity of the rock based on the density ranges in the table.

A. Coal

Explanation:

= water displaced by rock

Water displaced by rock = volume of water after rock is dropped into the cylinder - volume of water before the rock was dropped into the water

Water displaced by the rock = 180 ml - 150 ml = 30 ml

Density of rock:

40 grams => 30 ml

x grams => 1 ml

Cross multiply

1*40 = 30*x

40 = 30x

40/30 = 30x/30

1.3 = x

Density of rock = 1.3 g per 1 ml

Recall: 1 ml = 1 cm³

Therefore,

Density of the rock = 1.3 g/cm³

1.3 g/cm³ falls within the range of 1.1 - 1.4 g/cm³

Therefore, the rock is identified as Coal.

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