Unit-1 Nature of Science in Chemistry
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Unit-1 Nature of Science in Chemistry
Answer: Fuels release energy during burning (combustion), which is a chemical change.
Answer: Fractional distillation separates crude oil into fractions such as petrol and kerosene on the basis of their boiling points.
Answer: C6H12O6 is the molecular formula of glucose, a simple sugar produced during photosynthesis.
Answer: Soaps and detergents are cleaning agents that help to remove dirt and grease.
Answer: The stomach secretes hydrochloric acid (HCl), which helps in the digestion of food.
Answer: Plastics are polymers, large molecules formed from many repeating small units.
Answer: Vinegar is a dilute solution of acetic acid (CH3COOH) used in food.
Answer: A law is a concise statement of observed behaviour, while a theory is a tested explanation of those observations.
Answer: All organic compounds contain carbon, which is the basis of organic chemistry.
Answer: Table salt is sodium chloride (NaCl).
Answer: Energy is the capacity to do work or to produce a change.
Answer: Baking soda is sodium bicarbonate (NaHCO3), used in cooking and baking.
Answer: Water decomposes as 2H2O -> 2H2 + O2, so hydrogen at the cathode is collected in double the volume of oxygen.
Answer: An element is the simplest form of matter that cannot be decomposed into simpler substances by chemical reactions.
Answer: Washing soda is sodium carbonate (Na2CO3), used for cleaning.
Answer: In a compound, elements are chemically combined in a definite fixed ratio of atoms and mass.
Answer: Vitamin C is ascorbic acid, which is essential for health.
Answer: A hypothesis is useful only if it can be tested by experiment, which either supports or rejects it.
Answer: Air is a mixture of gases such as nitrogen and oxygen whose proportions can vary, while water, carbon dioxide and salt are pure substances.
Answer: Iron is present in haemoglobin, which carries oxygen in the blood.