Kinetic Theory Flashcards
Describe the arrangement and movement of particles in solids
Strong forces of attraction between particles, particles are packed very closely together in a fixed and regular pattern. Atoms vibrate in position but can’t change position or move. Solids have a fixed volume, shape and high density
Describe the arrangement and movement of particles in liquids
Weaker attractive forces in liquids than in solids, particles are close together in an irregular, unfixed. Particles can move and slide past each other which is why liquids adopt the shape of the container they’re in and also why they are able to flow. Liquids have a fixed volume but not a fixed shape and have a moderate to high density.
Describe the arrangement and movement of particles in gases
No intermolecular forces, particles are in random movement and so there is no defined pattern. Particles are far apart and move quickly (around 500 m/s) in all directions, they collide with each other and with the sides of the container (this is how pressure is created inside a can of gas). No fixed volume, since there is a lot of space between the particles, gases can be compressed into a much smaller volume. Gases have low density.
Compare the relative energies of particles in solids, liquids and gases
Particles in a solid have the least amount of energy and particles in a gas have the most energy.
Melting
Melting is when a solid changes into a liquid. Requires heat energy which transforms into kinetic energy, allowing the particles to move Occurs at a specific temperature known as the melting point (m.p.) which is unique to each pure solid.
Melting Point?
The temperature at which the solid turns into liquid and has the same value as the freezing point.
Boiling
Boiling is when a liquid changes into a gas
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 within the liquid
Occurs at a specific temperature known as the boiling point (b.p.) 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 0ºC.
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 liquid’s surface at low temperatures, below the b.p. of the liquid
The larger the surface area and the warmer the liquid/surface, the more quickly a liquid can evaporate
No heat is required and evaporation occurs over a range of temperatures
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
No energy is required for condensation to occur and it takes place over a range of temperatures
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 also called sublimation (sometimes called deposition or desublimation)
Sublimation occurs at a specific temperature which is unique for a pure substance
Interconversion of solids, liquids and gases [PIC]
Brownian Motion
The random motion of particles suspended in a fluid. The movement occurs since the particles collide with other moving particles in the fluid.
Diffusion
The net movement of particles from area of
