Which of the following substances sublimes on heating?
A. Sugar
B. Sodium chloride
C. Iodine
D. Copper
Answer: Option C
Solution (By JKSSB Mock Tests)
Iodine directly converts from solid to violet vapor on gentle heating (sublimation). NaCl melts; sugar decomposes; copper melts at high temperature. Other sublimable substances: camphor, naphthalene, dry ice.
Explanation:
Eutrophication is the excessive richness of nutrients (mainly nitrates and phosphates from fertilizers and sewage) in a lake or other body of water. This causes a dense growth of plant life (algal blooms) and depletion of oxygen, killing aquatic animals and disrupting the ecosystem.
Explanation:
Water (H₂O) is a compound – a pure substance composed of two or more elements chemically combined in a fixed ratio. Oxygen is an element. Air is a mixture of gases. Steel is an alloy (mixture). Compounds can be broken down by chemical methods.
Explanation:
Covalent bonds are formed by the sharing of electrons, which typically occurs between two non-metal atoms that have high electronegativities and a tendency to gain electrons. Metals tend to lose electrons, forming ionic bonds with non-metals. Noble gases are generally inert and do not form bonds.
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