Chapter 2: Kinetic particle theory 🧊💦

Question 1

What is the kinetic particle theory?

Answer 1

• Kinetic particle theory states that all matter is made up of tiny particles which move randomly all the time.

Question 2

What are the physical states that matter can exist in?

Answer 2

• Matter can exist in the physical states of solid, liquid, and gas.

Question 3

What are solids?

Answer 3

• Arrangement of particles: Very closely packed and arranged in an orderly manner.
• Forces of attraction between particles: Very strong
• Motion of particles: Vibrate or rotate about their fixed positions
  -Kinetic energy of particles: Very low
• Shape: Definite
• Volume: Definite
• Compressibility: Cannot be compressed.

Question 4

What are liquids?

Answer 4

• Arrangement of particles: Closely packed but arranged in a disorderly manner.
• Forces of attraction between particles: Less strong than the force of attraction between the particles in a solid.
• Motion of particles: Move freely throughout the liquid.
  -Kinetic energy of particles: Low but higher than the kinetic energy of the particles in a solid.
• Shape: Non-definite
• Volume: Definite
• Compressibility: Cannot be compressed.

Question 5

What are gases?

Answer 5

• Arrangement of particles: Very far apart and arranged in a disorderly manner.
• Forces of attraction between particles: Very weak
• Motion of particles: Move rapidly and freely in any direction.
  -Kinetic energy of particles: High
• Shape: Not definite
• Volume: Not definite
• Compressibility: Can be compressed.

Question 6

What is the strength of attractive forces between particles in a substance?

Answer 6

• The strength of attractive forces between particles in a substance depends on the distance between the particles.

Question 7

What is the factor that the average kinetic energy of the particles in a substance depends on?

Answer 7

• The average kinetic energy of the particles in a substance depends on temperature.

Question 8

When can matter change its state?

Answer 8

• A matter can change its state when heated or cooled.
• E.g. solid–>liquid–>gas

Question 9

What is the heat curve?

Answer 9

• The heating curve shows the changes that take place when a solid substance is heated.
  (e.g. heating curve: in revision guide)
  1.
• The temperature of the solid substance increases until it reaches its melting point.
• So, the kinetic energy of the particles in the solid increases, and the particles vibrate more quickly about their fixed positions.

2.
-The forces of attraction between the particles in the solid are overcome by the motion of the particles. (Faster motion, lesser forces of attraction, and slower motion, more forces of attraction.)
- Melting occurs and the substance changes from a solid to a liquid via heat gain.
- The temperature remains constant as melting occurs.

3.
- The temperature of the liquid substance increases until it
reaches its boiling point.
- The kinetic energy of the particles in the liquid increases, and the particles move more quickly.

4.
-The forces of attraction between the particles in the liquid are overcome by the motion of the particles.
- Boling occurs, and the substance changes from a liquid
to a gas.
- The temperature remains constant as boiling occurs.

5.
- Temperature of the gaseous substance increases.
- The kinetic energy of the particles in the gas increases, and the particles move more quickly.

Question 10

What is the cooling curve?

Answer 10

• The cooling curve shows the changes that take place when a gaseous substance is cooled.
  (e.g. cooling curve: in revision guide)
  1.
• The temperature of the gaseous substances decreases until it reaches its condensation point.
• Some kinetic energy of the particles in the gas is transferred to the surroundings as heat and the particles move more slowly.

2.
- The forces of attraction between the particles in the gas increases.
- Condensation occurs, and the substances change from a gas to a liquid during condensation.
- The temperature remains constant as condensation occurs.

3.
- The temperature of the liquid substance decreases until it reaches its freezing point.
- Some kinetic energy of the particles in the liquid is transferred to the surroundings as heat, and the particles then move more slowly.

4. • Forces of attraction between the particles in the liquid increase further, and the particles become closer and are arranged in a more orderly manner.
   • Freezing occurs, and the substances change from a liquid to a solid.
   • The temperature remains constant as freezing occurs.

5.
- The temperature of the solid substance decreases.
- Some kinetic energy of the particles in the solid is transferred to the surroundings as heat, and the particles vibrate about their fixed positions.

Question 11

Why is the boiling point of a substance the same as its condensation point?

Answer 11

• A pure substance boils and condenses at the same temperature, thus the boiling point of a substance is also its condensation point.

Question 12

Why is the freezing point of a substance the same as its melting point?

Answer 12

• A pure substance melts into a liquid and freezes into a solid at the same temperature, thus the melting point of a substance is also its freeing point.

Question 13

What is the melting and boiling point of oxygen?

Answer 13

• Melting point: -219°C
• Boiling point: -183°C

Question 14

What is the physical state of oxygen at different temperatures?

Answer 14

• Physical state at -196°C: Liquid as it is warmer than -213°C.
• Physical state at 25°C: Gas
• Physical state at 100°C: Gas

Question 15

What is the melting and boiling point of ethanol?

Answer 15

• Melting point: -114°C
• Boiling point: 78°C

Question 16

What is the physical state of ethanol at different temperatures?

Answer 16

• Physical state at -196°C: Solid
• Physical state at 25°C: Liquid
• Physical state at 100°C: Gas

Question 17

What is the melting and boiling point of iron?

Answer 17

• Melting point: 1535°C
• Boiling point: 2750°C

Question 18

What is the physical state of iron at different temperatures?

Answer 18

• Physical state at -196°C: Solid
• Physical state at 25°C: Solid
• Physical state at 100°C: Solid

Question 19

What is evaporation?

Answer 19

• Evaporation occurs when some particles at the surface of a liquid substance have enough energy to overcome the attractive forces between the particles and then escape into the air as a gas.

Question 20

What are the differences between boiling and evaporation?

Answer 20

1. Boiling occurs at the boiling point of a substance only, while evaporation occurs at temperatures below the boiling point of a substance.
2. Boiling occurs throughout a substance in the liquid state while evaporation occurs only at the surface of a substance in the liquid state.
3. During boiling, the temperature of the substance remains constant until all substances have changed into the gaseous state while during evaporation, the temperature if the substance decreases only.

Question 21

What does it mean when a liquid is said to be VOLATILE?

Answer 21

• Volatile liquids are liquids that evaporate easily, and such liquids usually have low boiling points.
• E.g. Instead of a normal 100°C, a volatile liquid’s boiling point can be 80°C, thus it turns into a gas faster as it is easier to reach 80°C than 100 from 0°C.

Question 22

what are some examples of volatile liquids?

Answer 22

• Ethanol (boiling point of 78°C)
• Propanone (boiling point of 56°C)

Question 23

What is sublimation?

Answer 23

• Sublimation is the process in which a substance in the solid state changes into the gaseous state directly without going through the liquid state.

Question 24

When does the change in state from a solid to gaseous state takes place?

Answer 24

• The change in state from solid to gaseous takes place when the particles at the surface of the solid possess sufficient energy to break away from the solid and thus escape as a gas.

Question 25

What are some examples of sublimation?

Answer 25

• Substances that undergo sublimation are iodine, dry ice (carbon dioxide in the solid state), ammonium chloride and naphthalene.

Question 26

What is vapour deposition?

Answer 26

• Vapour deposition is the reverse of sublimation, and it is the process in which a substance in the gaseous state changes into a solid state directly without going through the liquid state.

Question 27

What is diffusion?

Answer 27

• Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.

Question 28

What are some examples of diffusion?

Answer 28

1. When blue copper (II) sulfate crystals are placed in a beaker of distilled water. A homogeneous pale blue solution is then formed upon standing.
2. When brown nitrogen dioxide gas is mixed with air, a homogeneous and light brown mixture is observed within a few minutes. This is when both the nitrogen dioxide particles and the air particles reach equilibrium, which is the equal concentration for both sides of the reaction.

Question 29

What does it mean by a solution that is homogeneous?

Answer 29

• A homogeneous mixture is a mixture where the components are uniformly distributed throughout the mixture and cannot be distinguished from one another.
• Every part of a homogeneous mixture has the same composition and properties as any other part in the solution.

Question 30

What happens when the rate of diffusion increases?

Answer 30

• The rate of diffusion increases as the speed of particles increases. because the particles move faster and mix more quickly, thus reaching equilibrium quickly.

Question 31

What are the factors affecting the speed of particles and the rate of diffusion?

Answer 31

1. Temperature
   - The particles move more quickly at higher temperatures, so the rate of diffusion increases when the temperature increases.
   - E.g. When the same amount of copper sulfate is placed in 2 beakers with water of different temperatures, a homogeneous pale blue solution is formed more quickly in the beaker containing water of a higher temperature.
2. Particle mass
   - Particles with a smaller mass move more quickly so the rate of diffusion decreases when particle mass increases.
   - E.g. Hydrogen chloride gas diffuses at a slower rate than ammonia gas as it has a greater particle mass Thus, when hydrogen chloride gas reacts with ammonia gas in a glass tube, the white ring of ammonia chloride is formed nearer to the end of the tube with hydrogen chloride gas.