Chemicals ensure that we have heat and power; that we can buy goods and clothing; and that we have continual access to telecommunication, media and music wherever we are. Many of the changes we observe in the natural world around us are actually caused by chemical reactions, such as the changing colours of leaves and the growth of a flower. Chemicals are a significant contributor to our economies. Sound chemical management across the lifecycle of a chemical – from extraction or production to disposal – is therefore essential to avoid risks to human health and the environment. Nevertheless, there are two sides to the coin. "chemicals are a blessing and a curse". Just as we keep the benefits of chemicals in our life, we must also take care to treat them with respect so as to minimise any harmful impact from exposure to them... Hope its helpful...
Chemicals  are mostly used in the laboratories nut they can also be used to identify some gases.