Notes on properties of compounds in chemistry

Physical properties can be observed or measured without changing the chemical identity of the substance. Examples include:

• Melting point: The temperature at which a solid turns into a liquid.
• Boiling point: The temperature at which a liquid turns into a gas.
• Density: The mass of a substance per unit volume.
• Solubility: The ability of a substance to dissolve in a solvent.
• Color, odor, and state of matter (solid, liquid, gas) are also physical properties.

Chemical properties describe a substance's ability to undergo a chemical reaction or change its composition. Examples include:

• Flammability: The ability to burn.
• Reactivity: How readily a substance combines with other substances.
• Acidity/Basicity: Tendency to donate or accept protons.
• Oxidation state: The hypothetical charge an atom would have if all bonds to atoms of different elements were fully ionic.

The properties of a compound are determined by its chemical composition (the types of atoms present) and its chemical bonding (how these atoms are connected). For example, water (H₂O) has different properties than hydrogen peroxide (H₂O₂) because of the different arrangement and number of atoms.