1. States of matter

Question 1

State the distinguishing properties of solids

Answer 1

Solids:
- Fixed volume, shape and a high density
- The atoms vibrate in position but can’t change location
- The particles are packed very closely together in a fixed and regular pattern

Question 2

State the distinguishing properties of liquids

Answer 2

Liquids
- Fixed volume but adopt the shape of the container (randomly arranged)
- Medium density
- The particles move and slide past each other
- Generally flows easily

Question 3

State the distinguishing properties of gases

Answer 3

Gases
- Not fixed volume, and take up the shape of the container
- Low density
- Can be compressed into a much smaller volume
- Particles are far apart and move randomly and quickly in all directions
- Collide with each other and with the sides of the container

Question 4

Explain melting in terms of kinetic particle theory

Answer 4

1. Temperature increases, thermal energy is absorbed and converted to kinetic energy
2. Particles vibrate so much that the solid expands until the structure breaks
   - This is when the solid melts into a liquid

Question 5

Explain evaporation in terms of kinetic particle theory

Answer 5

1. Substance is heated, particles gain more kinetic energy to move more and spread out
2. Some high particles at the surface gain sufficient energy to overcome the intermolecular forces
   - Allowing them to escape from the liquid’s surface at low temperatures (below b.p)

Question 6

Explain boiling in terms of kinetic particle theory

Answer 6

1. Substance is heated, particles gain more kinetic energy to move more and spread out
2. Some high particles at the surface gain sufficient energy to overcome the intermolecular forces
3. When B.P is reached, particles gain enough energy for bubbles of gas to form below the surface of a liquid and throughout
   - Allowing for liquid particles to escape

Question 7

Explain, in terms of kinetic particle theory, the effects of temperature on the volume of a gas

Answer 7

Volume of gas increases as temperature increases (proportional)
1. An increase of thermal energy is converted to kinetic energy in the particles
2. As the temperature increases, the particles in the gas move faster and spread out more
3. Collision occurs more frequently and causes the container walls to expand (e.g. hot air balloon)

Question 8

Explain, in terms of kinetic particle theory, the effects of pressure on the volume of a gas

Answer 8

Volume of gas decreases as pressure increases (inverse)
1. Increasing the pressure means that the particles are in a smaller volume (same number of particles)
2. Since pressure increases and the volume decreases, the molecules collide more frequently with the container walls
3. Too much pressure can cause explosion or gas leaking

Question 9

Describe and explain diffusion in terms of kinetic particle theory

Answer 9

• Particles are always in random motion
  1. They move quickly and collide with other particles and the container walls
  2. Particles move from high concentration to low concentration
  3. Collisions make particles change direction and spread out
  4. Eventually, particles are evenly distributed throughout the available space, resulting in an equal concentration everywhere

Question 10

Describe and explain the effect of relative molecular mass on the rate of diffusion of gases

Answer 10

○ How to find the relative molecular mass: add the relative atomic mass together (bottom number)
○ The lighter or lower the relative molecular mass, the faster the rate of diffusion of gases (travel faster & further)