Year 7 Chemistry: Particle Theory, States of Matter, and Separation Techniques

Comprehensive vocabulary flashcards covering the particle theory of matter, states of matter, physical changes of state, thermal expansion, solutions, and separation techniques (magnetic separation, filtration, evaporation, chromatography, and distillation) for Year 7 Chemistry.

Matter

Anything that has a mass and volume.

Particle Model

A scientific model based on four main ideas: all matter is made of tiny particles, particles are always moving, particles have spaces between them, and adding heat makes particles move faster.

Solid

A state of matter where particles are tightly packed in a fixed arrangement and vibrate only in place, giving it a fixed shape and fixed volume.

Liquid

A state of matter where particles are close together but can move past each other, allowing it to flow and take the shape of the container while maintaining a fixed volume.

Gas

A state of matter where particles are spread far apart and move quickly in all directions, resulting in no fixed shape, no fixed volume, and a lower density.

Atom

The smallest unit of matter found on Earth, which is too small to be seen under a microscope.

Compression

The ability to reduce the volume of a substance by pressing its particles closer together into the empty spaces between them.

Melting

The physical change of state where a solid absorbs heat energy and changes into a liquid.

Freezing

The physical change of state where a liquid is cooled, loses kinetic energy, and changes into a solid.

Evaporation

The physical change of state where a liquid absorbs heat energy and changes into a gas.

Condensation

The physical change of state where a gas cools, loses kinetic energy, and changes into a liquid.

Sublimation

The physical change of state where a solid transitions directly into a gas without first becoming a liquid, such as dry ice ($CO_2$) at $-78.5^\times\text{C}$.

Deposition

The physical change of state where a gas transitions directly into a solid without first passing through the liquid phase.

Physical Change

A change in which a substance alters its physical state or form, but no new substance is formed and the particles remain identical before and after the change.

Melting Point

The specific temperature at which a solid substance gains sufficient kinetic energy to overcome attractive forces and become a liquid.

Boiling Point

The specific temperature at which a liquid gains sufficient kinetic energy to change entirely into a gas.

Thermal Expansion

The increase in volume or length of a substance caused by heating, which makes its particles gain kinetic energy, vibrate or move faster, and spread further apart.

Thermal Contraction

The decrease in volume or length of a substance caused by cooling, which makes its particles lose kinetic energy, move more slowly, and move closer together.

Kinetic Energy

The energy of motion possessed by particles, which increases when temperature increases.

Diffusion

The net movement of particles from an area of high concentration to an area of low concentration due to constant random motion until evenly distributed.

Brownian Motion

The random movement of microscopic particles that results from continuous collisions with particles in the surrounding liquid or gas medium.

Pure Substance

A substance that consists of only one type of element or one type of compound, having uniform chemical composition.

Element

A pure substance made up of only one type of atom that cannot be broken down into simpler substances by chemical means.

Compound

A pure substance formed when two or more different elements are chemically bonded together in fixed ratios.

Mixture

A physical combination of two or more pure substances that are not chemically bonded together, can exist in varying ratios, and can be separated by physical means.

Solution

A type of transparent mixture formed when the particles of one substance (the solute) break up, separate, and spread out evenly into another substance (the solvent).

Solute

The substance that dissolves into another substance to form a solution.

Solvent

The substance that dissolves the solute to form a solution.

Dissolving

The process where solute particles separate from each other, move away from the solid crystal, and spread evenly throughout the solvent.

Soluble

Describes a substance that is able to dissolve in a given solvent.

Insoluble

Describes a substance that is unable to dissolve in a given solvent.

Dilute Solution

A solution that has a relatively small amount of solute dissolved in a large amount of solvent, representing a low concentration.

Concentrated Solution

A solution that has a large amount of solute dissolved in a given amount of solvent, representing a high concentration.

Saturated Solution

A solution in which no more solute can dissolve at a given temperature.

Magnetic Separation

A physical separation technique that utilizes a magnetic field to attract and separate magnetic materials (such as iron, steel, nickel, or cobalt) from non-magnetic materials.

Filtration

A physical separation method used to separate an insoluble solid from a liquid by passing the mixture through a porous barrier such as filter paper.

Filtrate

The clear liquid that passes through the filter paper during filtration.

Residue

The insoluble solid particles that are trapped and remain on the filter paper during filtration, or the solid left behind after evaporation or distillation.

Evaporation (Separation Method)

A physical method used to recover a dissolved solid solute from a solution by heating the liquid solvent until it escapes into the air as a gas.

Chromatography

A separation technique that separates components of a mixture based on their relative affinities for a stationary phase versus a mobile phase.

Mobile Phase

The moving liquid or solvent in chromatography that carries the mixture components through or along the stationary phase.

Stationary Phase

The non-moving solid support (such as filter paper) in chromatography that components adhere to as the mobile phase passes.

Origin

The starting baseline on the stationary phase in chromatography where the sample mixture is originally placed.

Solvent Front

The leading edge of the liquid mobile phase as it ascends the stationary phase during chromatography.

$R_f$ Value

The retention factor in chromatography, calculated as the ratio: $\text{R}_f = \frac{\text{distance travelled by the component}}{\text{distance travelled by the solvent}}$.

Distillation

A physical separation method that separates substances based on differences in their boiling points by heating the mixture to vaporise the lower boiling liquid and condensing it back into a liquid.

Distillate

The purified liquid that is vaporised, cooled, and collected in a separate container at the end of a distillation process.

Liebig Water Condenser

A glass cooling apparatus surrounded by flowing cold water that lowers the temperature of hot vapors to condense them back into liquid during distillation.