States and Changes of Matter

States of Matter

• Matter exists in three states: solid, liquid, and gas.
• The state of matter depends on the forces of attraction between particles.
• Solids have strong forces of attraction, holding particles in fixed positions, resulting in a definite shape and volume.
• Particles in solids vibrate about their positions; the hotter the solid, the more they vibrate.
• Liquids have weaker forces of attraction than solids, allowing particles to move past each other. They have a definite volume but no fixed shape.
• Particles in liquids move randomly, filling the container.
• Gases have very weak forces of attraction, allowing particles to move freely in all directions. They have no fixed shape or volume, filling any container they occupy.
• Particles in gases move randomly and quickly, spreading out to take up the entire container.

Changes of State

• Substances can change from one state to another through changes in energy.
• Melting is the change from solid to liquid, occurring at a specific temperature (melting point) when heat is added.
• Freezing is the change from liquid to solid, releasing energy at a specific temperature (freezing point).
• Evaporating (vaporization) is the change from liquid to gas, absorbing energy to break the forces of attraction.
• Condensation is the change from gas to liquid, giving off energy.
• Sublimation is the change from solid to gas, absorbing energy directly.

Diffusion

• Diffusion is the gradual movement of particles from regions of high concentration to regions of low concentration.
• The movement of particles is random and depends on their kinetic energy.
• Diffusion happens in both liquids and gases. The particles in diffusion collide, causing them to spread out.
• The rate of diffusion depends on temperature.

Filtration and Crystallisation

• Filtration is used to separate an insoluble solid from a liquid.
• Crystallisation is used to separate a soluble solid from a solution.

Chromatography

• Chromatography is a technique used to separate mixtures of substances based on their different affinities for a stationary phase (a solid or liquid) and a mobile phase (a liquid or gas).
• Paper chromatography separates substances by their different solubilities in a solvent.

Distillation

• Distillation is a separation technique used to separate mixtures of liquids based on their different boiling points.
• Simple distillation separates liquids with significantly different boiling points.
• Fractional distillation separates liquids with similar boiling points by using a fractionating column.

Atoms

• Atoms are the basic building blocks of matter.
• Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in energy levels (electron shells).
• Atomic number is the number of protons in the nucleus.
• Mass number is the sum of protons and neutrons.
• Isotopes of an element have the same number of protons but different numbers of neutrons.

Periodic Table

• The periodic table arranges elements in order of increasing atomic number.
• Elements with similar properties are grouped together in columns (called groups or families).
• Rows (periods) represent increasing electron shells.
• Elements can be metals, nonmetals, or metalloids based on their properties.

Electron Shells

• Electrons orbit the nucleus in energy levels called electron shells or energy levels.
• Each shell can hold a specific maximum number of electrons.
• The lower energy levels fill first.
• The outer energy level, or valence shell, is important in determining the chemical properties of an element.