Mixture:
A mixture is a combination of two or more substances that are physically combined and can be separated by physical means. In a mixture, the substances retain their individual properties and do not undergo any chemical changes. The components of a mixture can be present in any proportion and can be in different phases (solid, liquid, or gas).

Compound:
A compound, on the other hand, is a substance that is composed of two or more elements chemically bonded together in fixed proportions. Unlike mixtures, compounds have a definite chemical composition and exhibit unique properties different from the elements that make them up.

Key Differences:

Composition:
- Mixtures: Mixtures can have varying compositions where the proportion of components can be changed.
- Compounds: Compounds have a fixed composition with elements combined in specific ratios.

Physical Separation:
- Mixtures: Mixtures can be separated by physical means such as filtration, evaporation, or distillation.
- Compounds: Compounds cannot be separated by physical means but require chemical reactions to break the bonds between elements.

Properties:
- Mixtures: The properties of a mixture are the sum of the properties of its individual components. Each component retains its own properties.
- Compounds: Compounds have unique properties different from the elements that form them. They often exhibit new properties that are not observed in the individual elements.

Chemical Composition:
- Mixtures: In mixtures, the substances are physically combined and can exist in different phases.
- Compounds: Compounds are chemically combined, and the elements lose their individual identities to form a new substance with different properties.

Examples:
- Mixtures: Examples of mixtures include air (a mixture of gases), saltwater (a mixture of salt and water), and trail mix (a mixture of nuts, seeds, and dried fruits).
- Compounds: Examples of compounds include water (H2O), carbon dioxide (CO2), and sodium chloride (NaCl).

Summary:
In summary, mixtures are combinations of substances that can be separated by physical means and retain the properties of their individual components. Compounds, on the other hand, are substances formed by the chemical combination of elements in fixed proportions and exhibit unique properties. While mixtures have variable compositions and can exist in different phases, compounds have fixed compositions and require chemical reactions for separation.