Final answer:
The statement is false because covalent compounds generally do not dissociate into ions in water, thus they cannot conduct electricity.
Step-by-step explanation:
The statement 'All covalent compounds conduct electricity when dissolved in water' is false. Conductivity measurements show that covalent compounds, if soluble, do not dissociate into ions in water. Since they stay as neutral molecules, they cannot carry an electrical charge, thus they do not conduct electricity. Only compounds that dissolve and disassociate into freely moving ions can conduct electrical current in solution. For instance, ionic compounds are known to conduct electricity when dissolved in water because the ions can move freely and carry charges.