Chemistry nature of partoculate matter

What is an element?

An element is a pure substance made of only one type of atom. Elements are the primary constituents of matter and cannot be broken down into simpler substances by chemical methods.

What is a compound?

A compound is a pure substance made of two or more different elements chemically bonded together in a fixed ratio.

What is a mixture?

A mixture contains two or more substances that are not chemically bonded. The substances can be present in variable proportions and can be separated by physical methods.

What is a homogeneous mixture?

A homogeneous mixture has a uniform composition throughout. Its components are evenly distributed and cannot usually be distinguished by eye. Example: salt water.

What is a heterogeneous mixture?

A heterogeneous mixture does not have a uniform composition throughout. Different components or phases can be distinguished. Example: oil and water.

What is the difference between a compound and a mixture?

A compound contains elements chemically bonded in a fixed ratio, while a mixture contains substances that are not chemically bonded and can be separated by physical methods.

What is filtration?

Filtration is a separation method used to separate an insoluble solid from a liquid. The mixture passes through a filter: the liquid passes through as the filtrate while the solid is trapped as the residue.

How does filtration work?

Filtration works because the filter has tiny pores that allow liquid particles to pass through but prevent larger insoluble solid particles from passing through.

What is distillation?

Distillation is a separation method based on differences in boiling points. It can separate a liquid from dissolved substances or separate liquids with different boiling points.

How does distillation work?

The mixture is heated so the substance with the lower boiling point vaporizes first. The vapour is then cooled in a condenser and turns back into a liquid called the distillate.

What is recrystallization?

Recrystallization is a technique used to purify a solid chemical compound by dissolving it in a suitable hot solvent and then allowing pure crystals to form as the solution cools.

How does recrystallization work?

The impure solid is dissolved in a minimum amount of hot solvent. As the solution cools, the desired compound crystallizes while many impurities remain dissolved. The crystals are then filtered and dried.

What is chromatography?

Chromatography is a separation and analysis technique used to separate components of a mixture based on their different interactions with a stationary phase and a mobile phase.

How does chromatography work?

A mixture is placed on a stationary phase. A mobile phase moves through it, carrying substances at different speeds depending on their solubility and attraction to the stationary phase. This separates the components.

What can chromatography be used for?

Chromatography can be used to separate and identify substances in mixtures, including analysing the contents of medicines.

What are the three main states of matter?

Solid, liquid and gas.

What is the particle arrangement in a solid?

Particles are closely packed in fixed positions and can only vibrate around these positions. Strong attractions hold the particles together.

What is the particle arrangement in a liquid?

Particles are close together but are not fixed in position. They can move and slide past one another because some intermolecular attractions have been overcome.

What is the particle arrangement in a gas?

Particles are far apart and move freely and rapidly in random directions. There are very weak or negligible attractions between particles.

What happens to particles when a solid melts?

Particles gain kinetic energy and vibrate more strongly until they overcome enough attractions to move past one another. The solid changes into a liquid.

What is melting?

Melting is the phase change from solid to liquid. It requires energy, so it is endothermic.

What happens to particles during evaporation?

Some particles at the surface of a liquid gain enough kinetic energy to overcome intermolecular attractions and escape into the gas phase.

What is evaporation?

Evaporation is the change from liquid to gas that occurs at the surface of a liquid. It requires energy and is endothermic.

What is boiling?

Boiling is the rapid change from liquid to gas throughout the liquid when the vapour pressure equals the external pressure. It requires energy and is endothermic.

What happens to particles during condensation?

Gas particles lose kinetic energy, move closer together and form stronger intermolecular attractions as they become a liquid.

What is condensation?

Condensation is the phase change from gas to liquid. It releases energy, so it is exothermic.

What happens to particles during solidification/freezing?

Liquid particles lose kinetic energy and become fixed in an ordered arrangement as stronger attractions hold them in place.

What is solidification/freezing?

Solidification or freezing is the phase change from liquid to solid. It releases energy, so it is exothermic.

What is sublimation?

Sublimation is the direct phase change from solid to gas without passing through the liquid state. It requires energy, so it is endothermic.

What happens to particles during sublimation?

Solid particles gain enough energy to overcome intermolecular attractions and move directly into the gas phase.

What is deposition?

Deposition is the direct phase change from gas to solid without passing through the liquid state. It releases energy, so it is exothermic.

What happens to particles during deposition?

Gas particles lose kinetic energy and become fixed into a solid structure as intermolecular attractions form.

Which phase changes are endothermic?

Melting, evaporation, boiling and sublimation are endothermic because energy is absorbed from the surroundings.

Which phase changes are exothermic?

Condensation, freezing/solidification and deposition are exothermic because energy is released to the surroundings.

What is the order of the states of matter from lowest to highest particle kinetic energy?

Solid → liquid → gas.

What happens to particle kinetic energy when temperature increases?

Average particle kinetic energy increases, so particles move or vibrate faster.

What is temperature?

Temperature is a measure related to the average kinetic energy of the particles in a substance.

What is the Celsius temperature scale?

The Celsius (°C) scale is a temperature scale commonly used in everyday situations. Water freezes at 0 °C and boils at 100 °C at standard atmospheric pressure.

What is the Kelvin temperature scale?

The Kelvin (K) scale is an absolute temperature scale used extensively in science. 0 K represents absolute zero, the theoretical minimum temperature.

How do you convert Celsius to Kelvin?

K = °C + 273.15.

How do you convert Kelvin to Celsius?

°C = K − 273.15.