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Two observations that indicate a chemical change are: (1) Formation of a new substance, such as a gas, precipitate, or color change. (2) Release or absorption of energy, like heat, light, or sound, during the reaction. 2025-26 sample paper question available ...
Both A and B are true but R is not the correct explanation of A. Baking soda is used in Soda acid fire extinguishers because it release is carbon dioxide gas upon reaction with H2SO4. CO2 helps put out fire ...
The correct option is [C]. Sodium carbonate decahydrate (Na₂CO₃·10H₂O), also called washing soda, is used to remove permanent hardness of water. It reacts with calcium and magnesium salts, forming insoluble carbonates, softening the water effectively. Download cbse sample paper for class ...
The correct option is [C]. When zinc granules react with sulphuric acid (X), zinc sulphate (ZnSO₄) forms and hydrogen gas (Y) is released. The hydrogen gas burns with a pop sound near a candle, confirming its identity. Tiwari Academy provides CBSE ...
The correct option is [B]. Sodium hydroxide is called an alkali because it is a base that dissolves in water, forming a basic solution. Ferric hydroxide, though a base, is insoluble in water and not termed an alkali. class 10 science ...
