States and Changes of Matter Quiz

Study Notes

Solids have a fixed volume and shape, high density, and tightly packed particles in a regular pattern called a lattice.
Liquids have a fixed volume but take the shape of their container, are generally less dense than solids (except water), and have loosely packed particles that move and slide past each other.
Gases have no fixed volume or shape, low density, and particles that are far apart and move randomly, quickly in all directions.

Melting is the process of a solid changing to a liquid, occurring at the melting point (m.p.) and requiring an increase in temperature.
Freezing is the reverse of melting, occurring at the freezing point, which is the same as the melting point of a pure substance, and requires a decrease in temperature.
Evaporation is the process of a liquid changing to a gas, occurring at the surface of liquids where high-energy particles escape, and happening over a range of temperatures.
Boiling is the process of a liquid changing to a gas, occurring at a specific temperature called the boiling point (b.p.) where bubbles of gas form throughout the liquid.
Condensation is the process of a gas changing to a liquid, taking place over a range of temperatures, and caused by cooling the gas, reducing the kinetic energy of its particles, and causing them to group together.

A heating curve shows how the temperature of a substance changes as it is heated from a solid to a gas.
A cooling curve shows how the temperature of a substance changes as it is cooled from a gas to a solid.
Both curves have plateaus where the temperature remains constant during phase changes (melting/freezing and boiling/condensing) because energy is being used to overcome intermolecular forces instead of increasing kinetic energy.

Pure substances are made of only one type of element or compound and have specific, fixed melting and boiling points, resulting in horizontal lines for phase changes on heating/cooling curves.
Impure substances are composed of more than one type of element/compound and are impure, resulting in lower melting points, higher boiling points, and phase changes that occur over a range of temperatures, represented by sloped lines on heating/cooling curves.

Gases can be compressed by increasing pressure, as the particles are pushed closer together.
Gases can expand by reducing pressure, as the particles have more space to move.
Gases expand when heated as the particles gain kinetic energy, move farther apart, and occupy a greater volume.
Gases contract when cooled as the particles lose kinetic energy, move closer together, and occupy a smaller volume.

Diffusion is the movement of particles from an area of high concentration to low concentration, down a concentration gradient, until equilibrium is reached.
This process happens in liquids and gases due to the random motion of particles and the presence of intermolecular spaces.
Diffusion occurs faster in gases than liquids because gas particles have higher kinetic energy and move faster.
For the same substance, diffusion is faster at higher temperatures and slower at lower temperatures.
Diffusion can be demonstrated by the reaction of ammonia (NH3) and hydrogen chloride (HCl) in a tube, where the white smoke of ammonium chloride (NH4Cl) forms closer to the HCl end because ammonia, being lighter, diffuses faster.

Lighter particles (lower molecular mass) diffuse faster than heavier particles (higher molecular mass).
Higher temperatures lead to faster diffusion due to increased kinetic energy.
Diffusion is a passive process, meaning it requires no external energy input.