Question

which is a characteristic of mixtures?
○ they are chemically bonded together.
○ they can be classified as pure substances.
○ they have fixed ratios between their components.
○ they can be separated by physical processes.

Explanation:

1. Analyze the first option: Mixtures are not chemically bonded; chemical bonding is for compounds. So this is incorrect.
2. Analyze the second option: Mixtures are combinations of substances, not pure substances (pure substances are elements or compounds). So this is incorrect.
3. Analyze the third option: Mixtures have variable ratios of components (unlike compounds which have fixed ratios). So this is incorrect.
4. Analyze the fourth option: Mixtures can be separated by physical processes (like filtration, distillation) since their components are not chemically bonded. This is a key characteristic of mixtures.

Answer:

D. They can be separated by physical processes.