Class 7 Science — Chapter 2: Exploring Substances: Acidic, Basic, and Neutral

What you'll learn

• ▸Acid-Base Indicators
• ▸Litmus as a Natural Indicator
• ▸Identifying Acidic Substances
• ▸Identifying Basic Substances
• ▸Neutral Substances
• ▸Common Acids in Edible Substances
• ▸Preparing and Using Other Natural Indicators
• ▸Application of Acidity/Basicity in Soil

Chapter Summary

--- PAGE 1 --- 2 Exploring Substances: Acidic, Basic, and Neutral On 28 February, the school hosted a science fair to celebrate National Science Day. At the entry gate, siblings Ashwin and Keerthi were greeted with a white sheet of paper. They were curious to know why a white sheet of paper was given to them! A few steps ahead, there was a volunteer spraying a liquid on these sheets of paper. The siblings also got their white sheets sprayed. To their surprise, the words 'Welcome to the Wonderful World of Science' appeared on the papers the moment the liquid was sprayed (Fig. 2.1). They were excited and eager to know how this happened and the reason behind it. Their curiosity was partly satisfied at the 'Colourful World of Substances' stall. They saw many activities showing colour changes on mixing different substances. They decided to explore these changes further. Let us join them on this learning adventure. 0777CH02 National Science Day Explore! Enquire! Enjoy! Welcome to the won…

Practice Questions from this Chapter

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1. Show other natural indicators. Get Solution →
2. Explore common acids in everyday foods. Get Solution →
3. Discover surprising uses for bases. Get Solution →
4. What is the natural source of litmus, a common acid-base indicator? Get Solution →
5. What color does blue litmus paper turn when an acidic substance is applied to it? Get Solution →
6. According to the text, substances that turn red litmus paper to blue are classified as what? Get Solution →
7. Substances like tap water or sugar solution, which do not change the color of either red or blue litmus paper, are described as being what? Get Solution →
8. What is the characteristic taste of edible acidic substances like lemon juice and amla? Get Solution →

Did you know?

• 💡 Your stomach acid can dissolve metals, but a special lining keeps you safe.
• 💡 Slugs and snails produce a basic, slippery mucus to move around and protect themselves.
• 💡 The color of some flowers can change if the soil they grow in becomes more acidic or basic.
• 💡 Ancient Egyptians used vinegar, an acid, to clean and preserve objects thousands of years ago.
• 💡 Some fish can sense tiny changes in water's acidity and move to find the perfect neutral spot.

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