Chemistry Year 9 units 1-2

Diffusion

The movement of one type of particle into another type and when particles move from an area of high concentration to an area of low concentration

Equilibrium

Uniform concentration where net diffusion stops

Concentration gradient

The difference in concentration that drives diffusion

Why diffusion happens?

Particles in gases and liquids are always moving by kinetic energy and this means they’re always in a random, constant motion.

Why does diffusion barely happen in solids?

The particles in a solid cant go out of position and can only vibrate and it would need lots of kinetic energy for the particles to move which would make a liquid

Why is diffusion faster in gases than liquids?

The particles in a gas are more spread out and can move faster than liquid particles.

Why is diffusion faster at a high temperature?

It gives the particles more kinetic energy so the speed and chemical reactions are faster

Reasons why diffusion can occur faster

Higher temperature, less space for the particles to move, higher concentration gradient, higher surface area

Element

A pure substance made of only one kind of atom; it cannot be broken down into simpler substances by chemical means

Compound

A substance formed when two or more elements chemically combine in a fixed ratio

Mixture

A physical combination of two or more substances that retain their individual properties

Periods and Groups

Periods - The rows running across the table

Groups - The rows running vertical through table

Naming compounds

Without oxygen - Add -ide to the end and put the metal first

With oxygen - Add - ate to the end

If an acid - Add H to the beginning

Electrolysis

To split up a compound into its constituent elements

Soluble

Able to dissolve in a solvent

Insoluble

Does not dissolve appreciably

Solution

A homogeneous mixture of solute + solvent

Miscible

Two liquids that mix in any proportion

Immiscible

Two liquids that do not mix

Chromatography

Separating dissolved substances based on how quickly they move through a medium (like paper or a column). Different substances travel at different speeds depending on their solubility and how strongly they stick to the medium.

Stationary Phase and Mobile Phase

Stationary Phase - The solid medium (Chromatography paper)

Mobile Phase - The solvent that moves up the paper by capillary action.

Rf

Rf= distance travelled by sample / distance travelled by solvent

Interpreting causes of where substances are on chromatography paper

Substances that interact strongly with the stationary phase (e.g., via hydrogen bonding) travel less → lower Rf.

Substances that are more soluble in the mobile phase travel farther → higher Rf.

Filtering (Filtration)

Separating an insoluble solid from a liquid by passing the mixture through filter paper. The solid particles are too large to pass through the pores and get trapped, while the liquid (filtrate) passes through

Dissolving in Water then Filtering

A two-step process where you first dissolve a soluble substance in water, leaving behind any insoluble impurities. Then you filter to remove those insoluble bits. Finally, you'd typically evaporate the water to recover the dissolved solid.

Simple Distillation

Separating a solvent from a solution (or liquids with very different boiling points). The mixture is heated — the component with the lower boiling point vaporizes first, then the vapour is cooled and condensed back into a liquid in a separate container.

Fractional Distillation

Separating mixtures of liquids with similar boiling points (like crude oil or ethanol and water). Uses a fractionating column with temperature gradients — different components condense at different heights based on their boiling points.

Separating Funnel

Separating immiscible liquids (liquids that don't mix, like oil and water). The denser liquid sinks to the bottom and can be drained off through a tap, leaving the less dense liquid behind.

Sublimation

Separating a solid that sublimes (turns directly from solid to gas when heated) from a mixture. The sublimed solid can be collected by cooling the vapour back to solid on a cold surface.

Magnetism

Using a magnet to separate magnetic materials (like iron, nickel, cobalt) from non-magnetic substances in a mixture.