This chapter explains that substances around us have different chemical natures, which can be identified as acidic, basic, or neutral. It shows how simple observations and experiments help us understand these properties. By using indicators like litmus, flower extracts, turmeric, and even odours, we can test and classify substances. The chapter also explains how acids and bases react with each other in a process called neutralisation, which is useful in many day-to-day situations such as treating ant bites, improving soil quality, and managing industrial waste.
Key Points
Substances can be classified as acidic, basic, or neutral.
Acidic substances turn blue litmus red and usually taste sour.
Basic substances turn red litmus blue and feel slippery to touch.
Neutral substances do not change the colour of red or blue litmus paper.
Litmus is a natural indicator obtained from lichens.
Natural indicators like red rose extract, hibiscus, turmeric, and purple cabbage can also be used.
Red rose extract turns red in acids and green in bases.
Turmeric turns red in basic substances but remains yellow in acidic and neutral substances.
Some substances change their smell in acidic or basic conditions and are called olfactory indicators.
When an acid reacts with a base, neutralisation occurs, forming salt, water, and heat.
Neutralisation helps solve real-life problems like ant bites, acidic soil, and polluted water.
👉 👉By carefully observing, testing, and thinking scientifically, we can understand the nature of substances around us. Using this knowledge responsibly helps solve everyday problems and protects both human health and the environment.