1. Composition and Properties:
* Physical Combination: The original substances retain their individual properties and can be easily separated back into their components. For example, a mixture of sand and salt still has the properties of sand and salt. You can separate them by using their different densities (e.g., dissolving the salt in water).
* Chemical Substance: A chemical substance is formed when two or more elements chemically combine to form a new substance with entirely different properties from the original elements. For example, when hydrogen and oxygen combine chemically, they form water, a completely new substance with properties distinct from hydrogen and oxygen.
2. Bonds and Reactions:
* Physical Combination: The substances in a physical combination are held together by weak forces, like Van der Waals forces. There is no chemical reaction, and no new chemical bonds are formed.
* Chemical Substance: In a chemical substance, atoms are bonded together by strong chemical bonds (covalent or ionic). These bonds involve the sharing or transfer of electrons, resulting in a completely new compound with different chemical properties.
Let me know if you'd like more examples or further explanations!
