Final answer:
To separate the elements in water, electrolysis is used, which decomposes water into hydrogen and oxygen using an electrical current.
Step-by-step explanation:
One method used to separate the elements in a compound such as water is electrolysis. Electrolysis involves passing an electrical current through water to break it down into hydrogen and oxygen gases.
This process is a chemical method of separation as it triggers a chemical change, unlike physical methods like filtration or distillation, which cannot decompose water into its elemental components.
Hence, electrolysis is used to separate the elements in water, which decomposes water into hydrogen and oxygen using an electrical current.