Particle Model Flashcards
6.3.1.1 Density equations (+ units)
Density = mass / volume P = m / v
Density = kg/m^3
= g/cm^3
Mass = kg
= g
Volume = m^3
= cm^3
6.3.1.1
Explain the difference In density between the states of matter
Density increases and the distance between the particles decrease
Solids = closely packed together in a regular arrangement, fixed position (very dense)
Liquids = particles are close to each other but can move around, in a regular arrangement (quite dense)
Gases = not close together, random arrangement (not dense)
6.3.1.1
Req practical 17
How do I measure the density of an irregular object?
To find mass use a measuring scale
To find volume use a displacement can and fill to the top, wait for the water to stop flowing out through the tube. Place a 25cm^3 measuring cylinder below the tube. Place irregular object in the displacement can. Collect all the water that flows out through the displacement can tube.
To find density use the mass / volume formula
6.3.1.1
Req practical 17
How do I find the density of a regular object
To find mass use a measuring scale
To find volume find the area of one side of the object then multiply by the length
To find density use the mass / volume formula
6.3.1.1
Req practical 17
What is uncertainty?
The uncertainty of a measurement is a number that indicates the confidence in a given answer, the larger the uncertainty the further the quoted value may be from the true value.
6.3.1.1
Req practical 17
How do I calculate absolute uncertainty?
Absolute uncertainty = range of measurement / 2
6.3.1.1
Req practical 17
How do I calculate percentage uncertainty?
% uncertainty = absolute uncertainty / average (mean) of the measurements x 100
6.3.1.1
Req practical 17
Advantages of using %uncertainty over absolute uncertainty?
% uncertainty makes it easier to compare to other objects/ answers
6.3.2
What is internal energy?
Energy stored inside a system by the particles (atoms and molecules) that’s make up a system, this is called internal energy.
Internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.
6.3.2
How does heating change the internal energy within a system?
Heating changes the energy stored within the system by increasing the energy of the particles that make up the system, this either:
raises the temperature of the system
OR
produces a state change
6.3.2.2
What is specific heat capacity
The amount of energy required to increase the temperature of 1 kg of the substance by one degrees Celsius
6.3.2.2
Specific heat capacity formula (+units)
(Given in exam)
Change in thermal energy = mass x specific heat capacity x temperature change
Change in thermal energy = joules (J)
Mass = Kg
Specific heat capacity = J/kg °C
Temperature change e= °C
6.3.2.2
Finding the specific heat capacity for vegetable oil
Measure mass of oil used.
Record the temperature of the oil every 60 seconds whilst heating.
Record the voltage and current (that should be the same for the whole expt)
Table with time, temperature and energy.
Equation:
E = i x V x t ( heating time)
Energy = current x voltage x time
6.3.2.2
Finding the specific heat capacity for vegetable oil / aluminium block graph
Temperature on Y Axis
Energy on X Axis
The graph is flat to start with then increases steadily
6.3.2.2
Finding the specific heat capacity for a block of aluminium
We use a power supply to heat a block of aluminium.
This apparatus can be connected to the power supply by either:
A joulemeter
A voltmeter and ammeter (and stop clock) [ E=IVt ]
To find the specific heat capacity of aluminium we must:
Measure the mass of Al to be heated.
Measure the initial temperature of the Al.
Turn on the heater and a stop clock.
Record the temperature of the Al at 60s intervals. Also record the energy input from the heater at these times.
Plot a graph
6.3.2.2
Specific heat capacity graphs:
Using the graph how do I find “C”
C (specific heat capacity) = 1 / mass x gradient
6.3.2
What is temperature?
A measure of the average internal energy of a substance
4.3.1.2
What changes as the temperature changes
The kinetic energy
4.3.1.2
What changes as the state changes
The potential energy
4.3.1.2
What’s the conservation of mass
That no atoms are lost or made during the reaction so the total mass of the product at the start = total mass of product at the end
4.3.2.3
What is the specific latent heat
The specific latent heat of a substance is the amount of energy required to change the state of 1kilogram of the substance with no change In temperature
The energy needed for a substance to change state is called latent heat. When a change of state occurs, the energy supplied changes the energy stored (internal energy) but not the temperature.
4.3.2.3
What is the latent heat of fusion
The energy required to change 1kg of a substance from a solid to a liquid with no change in temperature
4.3.2.3
What is the latent heat of vaporisation
The energy required to change 1kg of a substance from a liquid to a gas with no change in temperature
4.3.2.3
Latent heat formula (+units)
(Given)
Energy for a state change = mass x specific latent heat
E = m x L
Energy for a state change = Joules (J)
Mass = kg
Specific latent heat = (J/kg)
4.3.2.3
Latent heat and ice experiment
To measure the latest heat of fusion of energy used to melt the ice that was being tested:
The heaters attached to a joulemeter to see the energy input can be read directly from the screen.
To measure the mass we must consider the proportion of the melted ice that’s due to the heater, and subtract The proportion due to the temperature of the room.
Experiment set up:
A heater is connected to a Joule meter which is connected to a power supply. That heater is placed in the funnel with the ice in it which is in a Beaker. There is also another funnel which contains ice that’s also in a beaker.
We use this as the control so we can see how much ice has been melted from the heater and how much from the room.
4.3.3.1
What type of motion do gases move in
They move in a random motion to fill the room / container they’re put in
4.3.3.1
How is the motion of the molecules in a gas related to it’s temperature
At lower temperatures the particles have lower kinetic energy so there are fewer collisions per second and these collisions are lower energy collisions causing there to be low pressure
Higher temperatures the particles have a higher amount of kinetic energy so there are more collisions per second and these collisions have a higher amount of energy causing there to be high pressure
4.3.3.2
What happens to the pressure of a gas when the volume increases
The pressure decreases
The pressure of a gas is inversely proportional to the volume
4.3.3.2
Gas pressure equation
(Given)
Constant = p x V Constant = pressure (Pa) x volume (m^3)
EQUATION IS ONLY TRUE IF THE TEMPERATURE IS KEPT CONSTANT
4.3.3.2
Boyles law
P1 x V1 = P2 x V2
4.3.3.2
At what angle is the net force from the particles acting on a wall / container
Right angle (90°) The pressure produces a net drive at right angles to the wall of the gas / container
4.3.3.3
Describe the effect of doing work on an enclosed gas
(Bike pump example)
The gas particles colliding with the walls of the container apply a force at right angles to the walls of the container, this causes gas pressure.
If we compress the gas by applying force to the piston we have now carried out work (transfer of energy by force) on the gas. Because we have applied a force to the gas we’ve transferred energy to the gas particles.
This increases the internal energy of the gas (kinetic + potential energy).
Because we’ve increased the kinetic energy of the gas particles we’ve increased the temperature of the gas.
