CBSE Class 10 Science — Flashcards for Quick Revision

A: When magnesium ribbon burns in air, it forms magnesium oxide with a dazzling white flame. Balanced equation: 2Mg(s) + O₂(g) → 2MgO(s). This is a combination reaction because two reactants combine to f

A: Iron is more reactive than copper, so it displaces copper from copper sulphate solution. The iron nail gets coated with reddish-brown copper metal. Equation: Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s). Thi

A: When lead nitrate is heated, brown fumes of nitrogen dioxide are released. Balanced equation: 2Pb(NO₃)₂(s) → 2PbO(s) + 4NO₂(g) + O₂(g). This is a thermal decomposition reaction where a single compound

A: When zinc granules are added to dilute HCl, hydrogen gas is evolved with effervescence (bubbling). The reaction is: Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g). This can be tested by bringing a burning candl

A: Dry HCl gas does not produce H⁺ ions, so it shows no acidic properties. Only when HCl dissolves in water does it ionize: HCl + H₂O → H₃O⁺ + Cl⁻. The H₃O⁺ (hydronium) ions are responsible for acidic pr

A: Na₂CO₃(s) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + CO₂(g). Carbon dioxide gas is evolved. Test: Pass the gas through lime water [Ca(OH)₂]. Lime water turns milky due to formation of CaCO₃ precipitate: Ca(OH)

A: This demonstrates metallic lustre - the property of metals to have a shining surface when freshly cut or cleaned. The sandpaper removes the oxide layer, revealing the shiny metallic surface underneath

A: Metals like aluminum and copper are good conductors of heat. They efficiently transfer heat from the flame to the food, ensuring even cooking. Wood and plastic are poor conductors and would burn or me

A: Sodium reacts violently with water, producing sodium hydroxide and hydrogen gas. The reaction is highly exothermic and the hydrogen catches fire. 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) + heat energy