P1 Flashcards
What was Dalton’s model of the atom
He said atoms were small indestructible spheres where all atoms in an element where the same and each element has its own atoms
What was JJ Thomson’s model and how did he create it
He discovered cathode rays are made of particles less than 1-thousandth the size of a hydrogen atom.
He called these electrons
He decided electrons where embedded inside a positive mass (like a plum pudding) as they were negative and an atom was neutral.
Plums represented the electrons and the ‘pudding was the positive mass’
He believed the mas could be a solid or like a cloud
What was the Rutherford model
Ernest rutherford discovered some particles emit alpha particles
He fired these alpha particles at gold foil expecting them all to pass through, but some came back
To explain this he said an atom has a positively charged nucleus with electrons orbiting it
What did niehls bohr do
He stated that electrons orbited the nucleus in fixed electron shells
With Rutherford’s model the electrons would eventually crash into the nucleus
How big are atoms
1×10^-10m
What is density
How much mass can be found in a specific volume.
Mass ÷ volume
How do you calculate density
Density (kg/m3) ° mass(kg) ÷ volume (m3)
Which is denser, a solid liquid or gas
The solid is the most dense, as the particles are packed together more tightly, allowing there to be more particles in the same area
What is conservation of mass
You have to add or remove mass for it to change. Particles will not appear or disappear during changes of state.
What is temperature
A measurement of the average kinetic energy of the particles in a material. It does not depend on the amount of material you have
What is kinetic energy / kinetic store
The energy associated with a kinetic store
A energy in a kinetic store is associated with a moving object calculated with Ke = 1/2mv^2
What is 0K in °C and what is 0°C in
K = kelvin
°C = degrees Celsius
0k = -273°C
0°C = 273K
If a temperature changes by 1°C it changes by 1 kelvin
What is the difference between thermal energy and temperature
Temperature tells you the average Ke of particles
The energy in a thermal store is measured in Joules and depends on how fast the particles are moving and vibrating.
INDIVIDUAL PARTICLES DO NOT GET HOTTER
What happens when you heat something up
Heating can
Change the energy stored within the system to increase temperature
Produce a change of state
Make chemical reactions occur
What is a physical change
Change, such as change in state, that does not result in a new substance being made - irreversible
What is a chemical reaction
Process in which substances react to form different substances
What factors are important to raise the temperature of an object
The temperature rise
The type of object (e.g. good / bad conductor)
The mass of the material
What is specific heat capacity?
The energy needed to raise the temperature of 1kg of a material by 1K (or 1°C )
What is internal energy
The energy of a system because of the arrangement and movement if particles within it
What energy does heating an object increase?
Its internal energy - relating to motion vibration and arrangement of the particles in the object
How do you calculate with specific heat capacity
Change in the thermal energy (J) =
Mass (kg) × SHC (J/Kg°C) × change in temperature
Why does specific heat capacity (SHC) make a difference?
It tells you how resistant a material is to a change in temperature.
Objects like saucepans that need to heat up quickly are made from materials with low specific heat capacities, as less energy is needed to heat up the material
What is sublimation
When a solid turns into a gas
What is depositing
When a gas turns into a solid
When you boil water ir melt ice why is there no temperature rise?
The internal energy increases but the temperature does not.
The energy transferred is being used to break the attractive bonds between water molecules
What is specific latent heat of fusion (or melting)
The energy transferred when 1kg of a substance changes from solid state to liquid state or from liquid state to solid state
What is specific latent heat of vaporisation
The energy transferred when 1kg of a substance changes from a liquid to gas
How do you calculate with specific latent heat
Thermal energy for a change in state = mass (kg) × Specific latent heat (J/kg)
Why do gasses exert pressure?
The gas particles collide with the walls of a container, each collision producing a very small force.
With many collisions we have a greater force on the walls, causing the container to expand.
If we add more particles to an object that cannot expand the pressure increases
How does temperature affect gas
The particles will have a higher average speed, so the number of collisions is greater and more FREQUENT. This means a greater force is produced over the same area, so a greater pressure is produced
Pressure calculation using force and area
Pressure = force ÷ area
How can you measure pressure and what is it measured in
You measure pressure using a pressure gauge, and it is measured in Pascals (Pa) which is equal to N/m2
What would happen to pressure at 0k
There would be no pressure as the air particles have no energy at absolute zero
How are pressure and volume proportion
As volume doubles pressure halves
As volume halves pressure doubles
How do you calculate with pressure and volume
Pressure × volume = constant
How does putting work on gas affect temperature
Putting pressure on gas increases its ke
This means the temperature will increase
What is atmospheric pressure
The gas pressure caused by the atmosphere due to the density of the air at that height equal to aproximately 100kPa at the surface of the Earth
This means there is a force of 100kn on each m2 of the earth
Why do cans collapse if you pump the air out of them
By taking the air out of them there is no more pressure inside the can. Due to this, the forces of the atmospheric pressure will push it in.
What happens to atmospheric pressure as you go up
As there are less particles above you, a lower force will be exerted - atmospheric pressure will be lower
Why would a bag of crisps increase in size when going up
As they are packaged at ground level they will have an atmospheric pressure equal to the level they are packaged at.
As the forces pushing outwards from the inside of the packet, and inward from the outside of the packet there is no change in shape..
When going upwards (e.g in a aeroplane )
The atmospheric pressure outside the packet decreases, breaking the equillibrium.
As the forces inside is greater the packet will expand
What is liquid pressure
The pressure in a liquid due to the weight of liquid above it
What happens to the pressure as you travel further down in water
The pressure increases as there is a greater weight of water particles above you
How do you calculate liquid pressure
Pressure = height of column (m) × density of liquid (kg/m3) × gravitational field strength
What happens to pressure in a denser liquid
If the liquid is denser and the height is the same, the pressure will be greater
How can we use a water bottle to display liquid pressure
Fill a water bottle up with water
Poke holes in the bottle and watch the water come out.
The lowest hole will come out a greater distance as the pressure is higher
How do you find the difference of pressure between two depths
Calculate the pressure at each depth
Then subtract the smaller pressure for the larger pressure from the smaller
What is upthrust
The force on an object in a fluid due to the difference in pressure in the fluid acting on the area of the object
Why do you float
The water exerts a greater force on you upwards than the water exerts on you downwards
What is the (basic) calculation for pressure
Pressure = force ÷ area
Using area and pressure how do you calculate weight
(pressure at bottom × area at bottom) - (pressure at top × area at top) = weight
Top force - bottom force = weight
Why do some objects float
If the pressure force with an area is big enough the net force will balance the weight and the object will stay where it is
Why do some objects sink
If the weight is greater than force of upthrust the object will begin to sink
How do submarines float and sink
When at the surface they increase their weight by letting water into air tanks. This causes the submarine to sink
To move back they pump air into these tanks, decreasing the weight
This is similar to how fish swim
How does density change with volume
When volume is doubled density is halved
They are inversely proportional
When a fluid is compressed in a plunger how is force applied to the fluid
A force is applied at 90° to all points on the surface fluid
