Chemistry Context

Study Notes

Chemistry is the science of substances' properties, composition, and structure, including transformations and energy changes.
Physical properties of matter include length, color, density, mass, elasticity, pressure, and volume.
Chemical properties of matter include toxicity, oxidation, heat of combustion, stability, flammability, coordination number, and reactivity, along with chemical bonds and enthalpy of formation.
States of matter are solids, liquids, gases, and plasma.
- Solids have rigid structure with fixed shape and volume; molecules vibrate within limited space.
- Liquids have a fixed volume but take the shape of their container; molecules flow.
- Gases have no fixed shape or volume; molecules move freely.
- Plasma is a high-temperature state where atoms lose electrons, forming a mix of electrons and nuclei.

Melting point is the temperature where a substance changes from solid to liquid.
Freezing point is the temperature where a substance changes from liquid to solid.
Pure water's melting and freezing point is 0°C.

Water is essential for life, covering 70% of Earth's surface.
It's a major component of living organisms (up to 95%).
The chemical symbol for water is H₂O.
A water molecule consists of two hydrogen atoms and one oxygen atom.
Water is a universal solvent, dissolving many substances.
Most abundant form of water on Earth is saltwater.
The water cycle involves continuous movement of water on, above, and below Earth's surface.

Mixtures result from combining two or more substances.
- Mixtures can be homogeneous (uniform composition; components not easily identified) or heterogeneous (non-uniform; components distinct).
Solutions are homogeneous mixtures.
- Solutions are made of a solvent (usually more abundant) and a solute (dissolved substance).
Components of mixtures can be present in various proportions.