Changes in State

- Solids: Strong forces of attraction hold particles close together in a fixed, regular arrangement. Particles don't have much energy and only vibrate about fixed positions.

- Liquids: Weaker forces of attraction between particles. Particles are close together but can move past each other to form irregular arrangements. They have more energy than solids.

- Gases: There are almost no forces of attraction between particles. Particles in gases possess more energy than those in solids and liquids, allowing them to move freely and travel at high speeds in random directions.

- Temperature: The average kinetic energy of particles.

- Heating liquid (boiling): This process transfers extra energy to particles' kinetic energy stores, causing them to move faster. When enough particles have enough energy to overcome their mutual attractions, large bubbles of gas form.

- Heating solid (melting): Extra energy causes particles to vibrate faster until the forces between them are partly overcome and the particles start to move around.

- When a substance is melting or boiling (+ graph plateaus), energy is used for breaking intermolecular bonds; rather than raising the temperature, the substance stays at a constant temperature.
- When a substance is condensing or freezing (+ graph plateaus), bonds are forming between particles, which releases energy; temperature doesn't decrease until all substances have changed states.

Evaporation:

- Particles escape from a liquid and transform into gas particles.
- Particles can evaporate from a liquid at a temperature much lower than its boiling point.
- The particles can do this if:
→ Particles are traveling in the right direction to escape the liquid.
→ Particles are travelling fast enough (have enough energy in kinetic energy stores) to overcome attractive forces of the other particles in the liquid. 
- The fastest particles (i.e., with the most KE) are most likely to evaporate from liquid first. 
→ The average speed and energy in the KE stores of the remaining particles decrease when they do this.
→ This lowers the temperature of the remaining particles.
- This cooling can be very useful: For example, when you exercise or become hot, the water from your sweat evaporates, cooling you down.

Temperature-Time Graph for Water:

- The experiment aims to demonstrate that the temperature remains constant during changes in state:
1. Fill the beaker with crushed ice. Insert the thermometer into the beaker and note the temperature of the ice.
2. Using a Bunsen burner, gradually heat the beaker. 
3. Every 20 seconds, record the temperature and current state of the ice in a table. Continue until the water starts to boil.
4. Plot a graph with temperature on the y-axis and time on the x-axis.

Flat spots on both graphs show changes in state.

Absolute 0:

- The coldest anything can get is -273°C or OK → absolute zero. 
→ Particles in KE stores have the least amount of energy possible.
- This is the start of the Kelvin Scale.
- To convert from degrees Celsius to Kelvin, add 273.
- To convert from Kelvin to degrees Celsius, subtract 273.

Specific Heat Capacity:

- Internal energy of substance = thermal energy store
→ Temperature is the measurement of the average internal energy of a substance.
- It takes more energy to increase the temperature of some materials than others.
→ For instance, it takes 4200 J to raise the temperature of 1 kg of water by 1°C, but it only takes 1345 J to raise the temperature of 1 kg of mercury by 1°C.
- Materials that gain lots of energy to warm up also release loads of energy when they cool down again.
→ They store a lot of energy for a given .
- The specific heat capacity of a substance is defined as the energy required to change the temperature of an object by 1°C per kg of mass, with water having a specific heat capacity of 4200J.

Finding the Specific Heat Capacity:

- You can use this method for water or any other liquid.
- Use a thermally insulated container (e.g., surrounded with wool) for these experiments to reduce heat loss to the surroundings.
→ The experimental value for specific heat capacity would be a bit higher since some of the heat supplied will be lost to surroundings.

1. Use mass balance to measure the mass of the insulating container.
2. Fill the container with water and measure the mass again.
→ Difference in mass = Mass of water in container
3. Make sure the joulemeter reads 0 and place it in the container. 
→ The heater was turned on, and the energy was calculated using the equation. (You can also use a voltmeter and ammeter) E = ItV
4. Measure the temperature of the water and then turn on the power.
5. Once the temperature has increased by, say, 10°C, turn off the power and record the temperature (increase and energy) on the joulemeter.
6. Calculate specific heat capacity by rearranging .
7. Repeat the full experiment 3x and calculate the average of c.

- Ensure that the material block you're using has two holes, one for the heater and one for the thermometer, to determine its heat capacity. Wrap up in an insulating material or layer.
- Once you've turned off the power and completed the timing, wait until the temperature stops rising before recording the highest or final temperature. This implies that the energy from the heater takes time to spread through the solid block.

Particle Theory:

- Particle theory says gases consist of very small particles that are constantly moving in completely random directions. These particles hardly take up any space, and most gas is empty.
- Particles constantly collide with each other and bounce off container walls.
- If you increase the temperature of a gas, you give particles more energy.
→ Double temperature in K = double average Particles store energy in KE. The KE of particles stores this energy.
→ The average energy of a gas in K is directly proportional to the average temperature of the gas in K (T).

- As gas particles move around, they collide with each other and whatever else is in the way (e.g., walls or surfaces).
- When they collide with something, they exert a force on it, resulting in a change in their momentum and direction.
→ For instance, it could lead to a change in pressure, similar to what happens when a balloon expands or when a flexible container is placed inside a fixed-volume container.
- This pressure depends on how quickly particles are moving and how often they hit container walls.
- If you heat a gas, the particles move faster and have more energy in KE stores. This results in a larger force and more collisions. More collisions result in a larger force, which in turn leads to increased pressure .
- If you put the same fixed amount of gas in a bigger container, pressure will decrease due to a lower force and a larger area .
- Container's walls = Fewer collisions between gas particles and container's walls. 
- As volume decreases, particles become more compressed.
- Walls more frequently = Produces larger force over smaller SA → increases pressure.