Temporary hardness is due to dissolved bicarbonates of Ca and Mg. These can be removed by boiling, which precipitates carbonates. Calcium sulfate and chloride cause permanent hardness. Sodium chloride does not cause hardness. Boiling: Ca(HCO₃)₂ → CaCO₃↓ + H₂O + CO₂. Bicarbonates are formed when water containing CO₂ passes over limestone.
Explanation:
Chadwick bombarded beryllium (Be) with alpha particles from polonium, producing a highly penetrating neutral radiation, which he identified as neutrons: ⁹Be + ⁴He → ¹²C + ¹n. Gold was used by Rutherford for nucleus discovery. Uranium for fission. Lead for shielding.
Explanation:
Glass is an amorphous (non-crystalline) solid; it lacks a long-range ordered structure. It is sometimes called a supercooled liquid. It softens over a temperature range rather than having a sharp melting point. Quartz (SiO₂) is crystalline.
Explanation:
Thermosets (e.g., Bakelite) form extensive cross-links between polymer chains, making them rigid. Heating breaks bonds but degrades, not remolds. Thermoplastics are linear/branched.
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