Question

For a science fair project about food and chemistry, Bill looks around his kitchen for examples of covalent compounds. What evidence can Bill use in his project to show that water (H2O) acts like other covalent compounds?

He can demonstrate that water is a liquid with a definite volume.
He can demonstrate that water can be boiled on a simple kitchen stove.
He can demonstrate that water can sometimes be used to conduct electricity.
He can demonstrate that water can change shape and either be sprayed or poured.

Answer 1

Use 1, 2 and 4 — not 3.

- Water being a liquid with a definite volume and changing shape / being pourable or sprayable (1 and 4) shows it behaves like a molecular (covalent) liquid rather than an ionic crystal.
- Boiling on a kitchen stove (2) shows it has a relatively low boiling point compared with ionic solids, which supports the idea of molecular (covalent) bonding.
- Water sometimes conducting electricity (3) is not evidence of covalent bonding — pure H2O is a very poor conductor; conductivity you see in the kitchen is from dissolved ions (salts), not from covalent water molecules themselves.