Interconversion between the States of Matter

the stronger the forces of attraction (between particles)

1. the more energy is needed to overcome them for a state change to occur

2. the higher the melting point and boiling point of the substance

when matter changes from one state to another

an interconversion of state

an interconversion of state

a physical change involving changes in the forces between the particles of the substances - the particles themselves remain the same, as do the chemical properties of the substance

melting

melting is when a solid changes into a liquid - the process requires heat energy which transforms into kinetic energy, allowing the particles to move - it occurs at a specific temperature known as the melting point, which is unique to each pure solid

boiling

boiling is when a liquid changes into a gas - this requires heat, which causes bubbles of gas to form below the surface of a liquid, allowing for liquid particles to escape from the surface and from within the liquid - it occurs at a specific temperature known as the boiling point, which is unique to each pure liquid

evaporation

when a liquid changes into a gas - evaporation occurs only at the surface of liquids where high energy particles can escape from the liquid’s surface at low temperatures, below the boiling point of the liquid - the larger the surface area and the warmer the liquid / surface, the more quickly a liquid can evaporate - evaporation occurs over a range of temperatures, but heating will speed up the process as particles need energy to escape from the surface

freezing

freezing is when a liquid changes into a solid - this is the reverse of melting and occurs at exactly the same temperature as melting, hence the melting and freezing point of a pure substance are the same (e.g. water freezes and melts and 0*C) - it requires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature which is unique for each pure substance

condensation

when a gas changes into a liquid, usually in cooling - when a gas is cooled its particles lose energy, and when they bump into each other they lack the energy to bounce away again, instead grouping together to form a liquid

sublimation

when a solid changes directly into a gas - this happens to only a few solids, such as iodine or solid carbon dioxide - the reverse action also happens and is called desublimation or deposition