Certain chemicals are substances made up of specific atoms and molecules that have distinct properties. They can be found in nature or created in laboratories. Examples include water, which is essential for life, and carbon dioxide, a gas produced by breathing and burning fossil fuels. Chemicals can be classified into different categories, such as acids, bases, and salts. Each category has unique characteristics and reactions. For instance, acids can taste sour and turn blue litmus paper red, while bases feel slippery and turn red litmus paper blue. Understanding these chemicals helps us in various fields, including medicine and environmental science.