Particle theory and states of matter

properties of a solid

- strong forces of attraction which holds them all close together

- fixed position

- definite shape and volume

- cannot be mixed

- tightly packed

what happens when a solid is heated

the particles gain kinetic energy and begin to vibrate more which weakens the forces between them, eventually the particles gain enough energy to break free of their bonds and turn into a liquid ( melting point)

properties of a liquid

- definite volume but can change shape

- weak forces of attraction

- compact

- shape can change/flow to fit a container

- free to move and slide over each other

what happens when a liquid is heated

the particles gain more kinetic energy and move around faster and collide into neighbouring particles, until the bonds are weakened enough and broken and the liquid evaporates into a gas (or boils)

properties of a gas

- low density

- indefinite shape and indefinite volume

- can flow to fill a container

- constantly moving with random motion colliding into walls and neighbouring gas particles

what happens when a gas is cooled?

the vibrations slow down, and so the particles won't have enough energy to overcome the forces of attraction so bonds will form, and it condenses into a liquid

what happens when a liquid is cooled?

particles lose kinetic energy and the vibrations slow down, so they won't have energy to overcome the forces of attraction and so more bonds form freezing the liquid into a solid

Explain why gases can be compressed, but solids and liquids cannot, in terms of particle arrangement.

• Gases: The particles in gases are far apart and move freely. Because there is a lot of empty space between the particles, gases can be easily compressed by pushing the particles closer together, also weak intermolecular forces

• Solids: In solids, the particles are closely packed in a fixed arrangement and do not have room to move much. This makes it impossible to compress solids as there is little to no space between the particles.

• Liquids: While the particles in liquids are closer together than in gases, they are still not in a fixed position. However, there is still not enough space between the particles to allow for compression.

difference between boiling and evaporation

boiling occurs throughout the entire liquid at a specific temp WHEREAS evaporation only happens at the surface and occur at any temp

why doesn’t a substance change temperature when changing state

• Energy is supplied, but temperature doesn’t change: Heat energy is used to change the state, not increase temperature.

• Energy breaks intermolecular bonds: The energy overcomes the forces holding the particles together.

• No increase in kinetic energy: The particles don’t speed up because the energy goes into breaking bonds.

• Temperature stays constant: The temperature remains the same during the phase change until it’s complete.

Explain why a substance expands when it is heated, using the particle model of matter.

• When a substance is heated, its particles gain kinetic energy, causing them to vibrate faster.

• The increased motion leads to more frequent collisions between particles, which causes them to move further apart.

• As a result, the substance expands, as the average distance between particles increases.