Boiling precipitates Ca/Mg bicarbonates as carbonates, removing temporary hardness. It does not remove permanent hardness (sulfates/chlorides). It kills microbes but does not remove dissolved salts.
Explanation:
Evaporation of water is a physical change—liquid water changes to water vapor, but the chemical composition (H₂O) remains unchanged. Souring of milk and curd formation involve lactic acid bacteria converting lactose to lactic acid (chemical change). Fermentation of grapes involves yeast converting sugars to ethanol and CO₂. Chemical changes produce new substances. Physical changes only alter the state or form.
Explanation:
Graphite conducts electricity due to delocalized electrons within its layers. Diamond is an insulator. Buckminsterfullerene (C₆₀) is a semiconductor but not as good a conductor as graphite in bulk; fullerene solids can be doped to become conductors. Charcoal is a poor conductor. Graphite electrodes are used in batteries and electrolysis.
Explanation:
The silver rod dissolves (Ag → Ag⁺ + e⁻) at the anode, replenishing Ag⁺ in the electrolyte, which deposits on the iron spoon (cathode). Iron spoon remains intact.
No comments yet. Be the first to start the discussion!