P1.2 Changes Of State Flashcards
What is density?
The amount of mass in a certain volume
It is a property of a material
Why can objects with the same volume have different masses
Because they have different densities
How do you calculate density (Kg/m3)
Density (kg/m3) = Mass (kg) ➗ volume (m3)
Why is a substance denser as a solid than as a liquid or gas?
In 1cm3 of a substance in the solid there are more particles than in 1cm3 of the same substance as a gas.
The mass of 1cm3 of the solid is greater so the density is also greater
What is temperature
It tells you how hot or cold something is
It is a measure of the average kinetic energy of the particles in a material
How many °C is 0K
-273°C
How many Kelvin is 0°C
273K
What happens in terms of energy transfer when you heat water?
- when you heat water you transfer energy from the chemical store of a fuel to the thermal store of the water
- the water particles move faster or vibrate more
What is the difference between energy in a thermal store and temperature?
- the energy in a thermal store is measured in Joules (J). It depends on the arrangement of the particles and how fast they are moving or vibrating
Temperature tells you about the average kinetic energy of the particles
What happens when you heat things up ?
Heating can:
- change the energy stored within the system to increase the temperature
- produce a change of state
- make chemical reactions happen
What is specific heat capacity?
The energy required to raise the temperature of 1Kg of a substance by 1K
What does the amount of energy needed to raise the temperature of an object depend on?
- the type of material
- the mass of material
- the temperature rise
What is the internal energy of a material?
The energy that relates to the motion, vibration, rotation and arrangement of the particles
How do you calculate the change in thermal energy with specific heat capacity?
Change in thermal energy (J) = mass (kg) ✖️ specific heat capacity (J/Kg°C)) ✖️ change in temperature (°C)
What does specific heat capacity tell you?
How resistant a material is to a change in temperature
Substances with a lower specific heat capacity heat up quicker
Substances with higher specific heat capacity are more resistant to temperature change
Why is water a good material to use in a central heating system
It is more resistant to temperature change as it has a higher specific heat capacity
Why are saucepans made of materials with low specific heat capacities?
Because they need to heat up quickly
What is a change of state?
The process of moving from one physical state to another
What is the process by which a liquid turns to a gas
Vaporising or boiling
What is the process by which a gas turns to a liquid
Deposition
What is the process by which a solid turns to a gas ?
Subliming
How can you investigate cooling?
- Melt salol in a test tube in a water bath. When the salol has melted place a thermometer in the test tube
- Remove the test tube from the water bath and place it in a test tube rack
- Take the temperature every minute and plot a graph of temperature against time
- Use the graph to find the temp at which salol solidifies
What happens when ice boils or melts
There is no temperature rise
The internal energy increases eventhough the temperature doesn’t
The energy that is transferred is breaking the attractive forces between the water molecules
What is the specific latent heat of fusion?
The energy transferred when 1Kg of a substance changes from the solid to the liquid state or from the liquid to solid state
What is the specific latent heat of vaporisation
The energy transferred when 1Kg of a substance changes from liquid to gas
How do you calculate the thermal energy for a change in state with specific latent heat?
Thermal energy for a change in state (J) = mass ✖️ specific latent heat (J/Kg)
What are similarities and differences between specific latent heat and specific heat capacity?
Similarity:
Both of them involve energy changes for 1Kg of a substance
Difference:
Latent heat is a change of state and heat capacity is about change of temperature
