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Class 7 Unit-8 (Materials used in Daily Life)

  Unit-8 (Materials used in Daily Life) Acids The compounds which have sour taste are called acids. Examples: Lemon juice, vinegar, hydrochloric acid. Physical properties of acids 1. Acids have sour taste. 2. Acids turn moist blue litmus to red. 3. Common acids are citric acid (in lemon), acetic acid (in vinegar), and sulfuric acid (in batteries). 4. Acids can burn skin.   Bases (Alkali) The compounds which have bitter taste are called bases. Examples: Soap, baking soda, lime water. Physical properties of bases 1. Bases have bitter taste. 2. Bases turn moist red litmus paper blue . 3. Bases react with acids to form salt and water . 4. Some bases are sodium hydroxide, calcium hydroxide, and ammonia .   Salts Salt can be defined as a compound formed by reaction of an acid with a base. Examples: Sodium carbonate, potassium chloride, copper sulphate, sodium nitrate, etc. Physical properties of salts 1. Salt is a su...
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Class 8 Unit-10 (Materials used in Daily Life)

  Unit-10 (Materials used in Daily Life) Acids The compounds which have sour taste are called acids. Chemically, acids are compounds which produce H + (proton) in water. Examples: Lemon juice, vinegar, hydrochloric acid. Physical properties of acids 1. Acids have sour taste. 2. Acids turn moist blue litmus to red. 3. Common acids are citric acid (in lemon), acetic acid (in vinegar), and sulfuric acid (in batteries). 4. Acids can burn skin.   Chemical Properties of acids: 1. Acids react with bases to form salt and water (neutralization reaction). 2. They react with carbonates to produce carbon dioxide gas . 3. Strong acids can corrode metals and burn skin , so they must be handled carefully.   1. Mineral Acids (Inorganic Acids) Mineral acids are acids that are obtained from minerals and do not contain carbon (except carbonic acid). They are usually strong acids . Examples: Hydrochloric acid (HCl) – found i...
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