12 Changes of State and SHC 4th Flashcards
What is the unit for Energy?
Joules
The total energy which matter possesses is called its internal energy.
This is the total kinetic and potential energy of all the particles.
Which state of matter possesses the most energy?
gas
Which material has the lowest specific heat capacity? How do you know?
aluminium
It requires less energy for the same temperature change as water.
Which state of matter has a fixed volume but an indefinite shape?
liquid - it has a fixed volume but can take the shape of its container
Describe the particle movement in a solid
- vibrating in fixed positions
What is the equation linking energy, mass, specific heat capactiy and change in temperature?
If the force of attraction between particles in a liquid is moderate, how does this change when in gaseous form?
- the force of attraction between particles is very weak or negligible, the particles move freely and are far apart in a gas.
What safety precautions must be taken when finding the specific heat capacity of water?
- heater and water will be hot- handle with care, let cool before clearing away
- water and electricity may lead to an electric shock- do not operate equipment with wet hand, check insulation on wires is intact before using.
Sketch a typical heating curve for a substance.
Name the three states of matter
solid, liquid and gas
gas to solid
Name the change of state
deposition
If ice from a cold freezer is put in a warm room, it absorbs thermal energy.
The ice warms up and begins to melt.
How does the temperature vary with time while the ice warms from -4°C to 4°C?
- as the ice warms up the temperature rises from -4°C to 0°C.
- at 0°C the temperature of the ice remains constant while the ice melts.
- when all the ice has melted the temperature begins rise again from 0°C to 4°C
How is kinetic energy of a substance related to its temperature?
Kinetic energy is proportional to the average kinetic energy of the particle in the substance
gas to liquid
Name the change of state
condensation
Describe the particle movement in a gas
- moving fast and moving freely
How is the energy supplied to the water calculated when finding the specific heat capacity of water?
E = IVt
Energy = Current (A) x voltage (V) x time (s)
Which state of matter possesses the most potential energy?
gas - particles are the furthest apart
solid to liquid
Name the change of state
melting
Which state of matter possesses the most kinetic energy?
gas - particles are moving the fastest
Explain the temperature change in the graph below.
- Q-R the energy supplied increases the kinetic energy of the particles- temperature increases
- R-S all the energy supplied goes into weakening intermolecular bonds to induce the state change- temperature stays constant
- S-T - the state change is completed- energy supplied increases the kinetic energy of the particles- raising the temperature once again.
Which material will cool more quickly?
aluminium
less energy needs to be removed for the same temperature drop.
What equipment is needed to find the specific heat capacity of an aluminium block?
- aluminium block, power supply, electric heater and thermometer
- stopwatch
- voltmeter
- ammeter
- lagging for top and side of block
- mat for bottom of block
Samuel used the equipment below to measure the specific heat capacity of water. His value was
5100 J/kg°C.
The true value is 4200J/kg°C.
Explain why his value is too big?
- Not all the energy supplied by the heater goes to the water, some is lost to heating the heater and to the surroundings - Q [energy supplied] is too big
E=IVt
- as a result the temperature change is too low
A bigger than expected Q divided by a smaller than expected change in T means the specific heat capacity will always be too big!
Which material has the highest specific heat capacity? How do you know?
water
It requires more energy for the same temperature change as aluminium.
solid to gas
Name the change of state
sublimation
liquid to solid
Name the change of state
freezing
liquid to gas
Name the change of state
evaporation
