2.1 States of matter Flashcards
Solids
A solid has a fixed shape because of the strong forces between its particles.
Solids cannot be compressed because their particles are already very close together and cannot flow.
The particles in a solid are arranged in an ordered pattern.
The particles in a solid move around a fixed point.
Solids are the densest state of matter.
The particles are packed tightly together.
Liquids
Liquids cannot be compressed because their particles are already very close together.
In a liquid, the particles are in contact with one another, but they can still move. This allows a liquid to flow and take the shape of its container.
Particles in a liquid are arranged in a disordered pattern.
Liquids are less dense than solids but denser than gases.
The particles in liquids can move around each other.
Gases
Gases can be compressed because their particles are very far apart.
When water evaporates to become steam (gas), its volume increases by 1000x.
The particles in a gas are free to move in any direction. Because of this, a gas can flow, has no fixed shape and completely fills its container.
The particles in a gas move randomly and are not organised in any way.
Gases are the least dense state of matter.
The particles are free to move with negligible forces between particles.
Interconversions
When matter changes from one state to another due to changes in temperature or pressure, the change is called an interconversion of state.
It is 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.
Physical changes are relatively easy to reverse as no new substance is formed during interconversions of state.
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 .
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 point and freezing point of a pure substance are the same.
Water for example freezes and melts at 0 ºC.
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.
Evaporation
When a liquid changes into a gas.
Evaporation occurs only at the surface of liquids where high energy particles can escape from the liquids 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.
Condensation
When a gas changes into a liquid, usually on cooling.
When a gas is cooled its particles lose energy and when they bump into each other, they lack 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 reaction also happens and is called desublimation or deposition.
