MediumChemistryHigh School (9–10)GeneralCarbon and Its Compounds › Covalent Bonding and AllotropesConceptual
Four white or colourless substances are tested.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Four white or colourless substances are tested.
- P melts at and conducts electricity when it is melted.
- Q melts at and does not conduct, solid or melted.
- R is a gas at room temperature, and it burns.
- S is a liquid that boils at and mixes with water, but does not conduct.
Which is likely to be ionic, and which covalent? Give a reason for each.
Need a reminder? The key ideaShow
Covalent compounds are made of molecules. The forces between the molecules are weak, so they melt and boil low, and they have no ions, so they do not conduct. Carbon forms millions of compounds because of catenation (chains, branches and rings) and tetravalency (four bonds).
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. P is ionic. Its melting point is high, and its ions can move once it melts.
Step 2. Q is covalent. It melts low and never conducts, so it is made of molecules.
Step 3. R is covalent. A gas at room temperature has weak forces between its molecules. Burning is typical of carbon compounds.
Step 4. S is covalent. It boils low and does not conduct. Some covalent compounds, such as ethanol and methanol, mix with water.
Answer: P ionic; Q, R and S covalent.
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