Acids-Bases-and-Salts.pdf/7th class science
- 1. Acids, Bases and Salts We use many substances in daily life like lemon, salt, and vinegar. These have different tastes due to their chemical nature. Some are acidic, some basic, and some neutral. This chapter explores acids, bases, and their properties. by sandeep swamy
- 2. Common Substances and Their Tastes 1 Sour Substances Lemon juice, orange juice, vinegar, and curd have a sour taste due to acids. 2 Bitter Substances Baking soda has a bitter taste and soapy feel, indicating it is a base. 3 Other Tastes Sugar is sweet, while common salt is salty. These are neutral substances.
- 3. Acids and Bases Acids Substances that taste sour and contain acids. The word "acid" comes from Latin "acere" meaning sour. Bases Substances that taste bitter and feel soapy. They do not contain acids.
- 4. Indicators Definition Special substances used to test if a solution is acidic or basic. Color Change Indicators change color when added to acidic or basic solutions. Natural Indicators Turmeric, litmus, and China rose petals are examples of natural indicators.
- 5. Common Acids in Nature Acetic acid Vinegar Formic acid Ant's sting Citric acid Citrus fruits Lactic acid Curd Oxalic acid Spinach
- 6. Common Bases in Nature Calcium hydroxide Lime water Ammonium hydroxide Window cleaner Sodium/Potassium hydroxide Soap Magnesium hydroxide Milk of magnesia
- 7. Litmus: A Natural Indicator 1 Source Extracted from lichens 2 Color in Water Mauve (purple) in distilled water 3 Reaction with Acids Turns red in acidic solutions 4 Reaction with Bases Turns blue in basic solutions
- 8. Testing Substances with Litmus Paper 1 Step 1 Mix water with test substance in a container. 2 Step 2 Put a drop of solution on red litmus paper. 3 Step 3 Observe any color change. 4 Step 4 Repeat with blue litmus paper.
- 9. Neutral Solutions Definition Solutions that do not change the color of either red or blue litmus. Nature Neither acidic nor basic. Examples Pure water, sugar solution, salt solution.
- 10. Turmeric as a Natural Indicator 1 Preparation Make a paste with turmeric powder and water. 2 Paper Making Deposit paste on filter paper and dry it. 3 Testing Put a drop of test solution on the turmeric paper.
- 11. China Rose as an Indicator 1 Preparation Soak China rose petals in warm water to extract color. 2 Acidic Reaction Turns dark pink (magenta) in acidic solutions. 3 Basic Reaction Turns green in basic solutions.
- 12. Testing Common Solutions Solution Litmus Turmeric China Rose Lemon juice Red No change Pink Soap solution Blue Red Green Salt solution No change No change No change
- 13. Acid Rain 1 Formation Pollutants like CO2, SO2, and NO2 dissolve in rainwater. 2 Acids Formed Carbonic, sulphuric, and nitric acids form in raindrops. 3 Effects Damages buildings, monuments, plants, and animals.
- 14. Safety with Acids and Bases Caution Laboratory acids and bases are corrosive and harmful to skin. Protection Wear protective gear when handling these substances. Emergency Know the location of safety equipment like eyewash stations.
- 15. Neutralization 1 Mixing An acid solution is mixed with a base solution. 2 Reaction The acid and base neutralize each other's effects. 3 Result A salt is formed, along with water and heat.
- 16. Phenolphthalein Indicator Acidic Solution Phenolphthalein remains colorless in acidic solutions. Basic Solution It turns pink in basic solutions. Neutralization Used to determine the endpoint of acid-base neutralization.
- 17. Neutralization Reaction Reactants Acid + Base Products Salt + Water Energy Heat is evolved
- 18. Indigestion and Antacids Cause Excess hydrochloric acid in the stomach causes indigestion and pain. Treatment Antacids like milk of magnesia (magnesium hydroxide) neutralize excess stomach acid.
- 19. Treating Ant Bites 1 Sting Ants inject formic acid into the skin when they bite. 2 Neutralization Apply baking soda (sodium hydrogencarbonate) or calamine solution (zinc carbonate). 3 Relief The base neutralizes the acid, reducing pain and irritation.
- 20. Soil Treatment Acidic Soil Treated with quick lime (calcium oxide) or slaked lime (calcium hydroxide). Basic Soil Treated with organic matter (compost) which releases acids.
- 21. Factory Waste Treatment 1 Problem Acidic factory wastes can harm aquatic life. 2 Solution Neutralize wastes by adding basic substances. 3 Result Treated water is safer for the environment.
- 22. Acids in the Human Body DNA Deoxyribonucleic acid controls our genetic features. Proteins Made of amino acids, essential for cell structure. Fats Contain fatty acids, important for energy storage.
- 23. Identifying Unknown Solutions Acid Turns blue litmus red, turmeric unchanged. Base Turns red litmus blue, turmeric red. Neutral No change in litmus or turmeric color.
- 24. Secret Messages with Acids and Bases 1 Writing Use baking soda solution to write invisible message. 2 Revealing Rub beetroot slice over the paper to reveal the message. 3 Science Acid in beetroot reacts with base, changing color.
- 25. Red Cabbage Indicator 1 Preparation Boil red cabbage in water to extract pigment. 2 Acidic Turns red in acidic solutions. 3 Neutral Remains purple in neutral solutions. 4 Basic Turns blue or green in basic solutions.