(5.8P-5.14P) Changes of state + SHC

Describe a solid.

Particles are:

• closely packed

• arranged in rows

• vibrate around fixed positions

• definite shape

• definite volume

Describe a liquid.

Particles are:

• closely packed

• can flow over each other

• no definite shape

• fixed volume

Describe a gas.

Particles are:

• far apart

• move randomly

• no definite shape

• no fixed volume

• highly compressible

Describe the change from solid → liquid.

• melting is a

• thermal energy transfer

• supplies particles in the solid with kinetic energy

• overcomes rigid bonds between the particles

• they can now flow

Describe the change from liquid → gas.

• evaporation

• thermal energy transfer

• supplies surface particles with kinetic energy

• breaks the bonds between the particles

What is the difference between boiling and evaporation?

Evaporation occurs at the surface of the liquid

Boiling causes gas bubbled to form within the liquid

What happens to temperature during a change of state?

stays constant during the process, rises or falls after

Why will heating a system change the energy stored within, raise the temperature or change the state?

• heating a system means

• kinetic energy of particles increases

  • temperature is related to avg. Ek

• this increase causes temp to rise

• or a change of state

Describe the experiment to obtain a temp-time graph for a change of state.

1. Have a beaker of ice with a thermometer on gauze, on a tripod, above a Bunsen burner.

2. Start to heat, taking regular temperature measurements.

3. Continue while it changes state and plot graph of values.

What should the graph show?

increasing, constant, increasing temperature

• while changing state, the temperature remains constant

What is specific heat capacity?

The energy needed to raise the temperature of an object by 1 degree Celsius per kg of mass

State the formula used to calculate the change in thermal energy.

ΔQ = mcΔT

change in energy =

mass * SHC * change in temperature

Describe the experiment used to investigate the SHC of materials.

1. Place beaker on balance set to 0.

2. Add 250ml of water, an immersion heater and thermometer.

3. Connect a circuit to record current and voltage to the heater.

4. Record initial temp of water and turn on power supply + stopwatch.

5. Record current, voltage + temp every minute for 10 mins.

6. Calculate energy and plot graph of energy against temp*mass so SHC is the gradient.