1. bromine is a a. black solid b. red liquid c. colourless gas d. highly inflammable gas 2. the hardest substance available on earth is a. gold b. iron c. diamond d. platinum 3. the variety of coal in which the deposit contains recognisable traces of the original plant material is a. bitumen b. anthracite c. lignite d. peat 4. tetraethyl lead is used as a. pain killer b. fire extinguisher c. mosquito repellent d. petrol additive 5. which of the following is used as a lubricant? a. graphite b. silica c. iron oxide d. diamond