P1 - Matter Flashcards
what was Dalton’s model of the atom + his thoughts
- small indestructible sphere
- thought that:
> all atoms in an element are the same - different elements have different atoms
what was JJ Thompson’s model of the atom + what he thought
- Plum Pudding model
> described the atom as a weak positive solid sphere with negative electrons embedded into it
> found this after an experiment which polluted cathode rays
what was Rutherford’s model like + how did he find out
- alongside two younger scientists they fired positive alpha particles at a thin sheet of gold
> found that most went through
> some deflected
> some completely rebounded - concluded that the atom is mostly empty space with most of its mass in the positive nucleus with electrons orbiting around
what was Bohr’s model
- electrons exist in fixed shells which orbit around the nucleus
what is the size of an atom
10 *-10 m
what is the size of a nucleus
10*-15 m
what is the size of a molecule
10*-8 m
how was the existence of neutrons + protons discovered
- by deep elastic scattering
> high speed electrons were fired at nucleus of atoms which showed diffraction pattern + showed that there was sub-structure to the nucleus of an atom
what is density
- tells you how much mass in contained within a volume
what’s the equation for density
density = mass / volume
kg/m3 = kg / m3
how do you find the density of an irregular shape
- fill eureka can with water until spout + place measuring cylinder under it
- measure mass of object
- slowly lower object into can
- water will be displaced + come out of spout because of objects more density
- the displaced water is measured and converted to m*3
- find density using equation
what is temperature + what’s it measured in
- the average kinetic energy of particles
- degrees Celsius or K (Kelvin)
what is thermal energy store + what’s it measured in
- thermal energy depends on the arrangement of particles + how fast they are moving / vibrating
- measured in joules
what happens when you heat things up
- increase the energy stored
- produce a change of state
- make chemical reactions happen
what are physical changes
- you don’t make new substances
> reversible e.g. changes of state
what are chemical changes
- involve atoms joining together in diff ways
> can’t easily reverse e.g. burning
why do solids have the most density
- because the particles are tightly packed together so there is more mass per unit volume
> gases have lowest density
what is specific heat capacity
- the amount of energy needed to raise a 1kg substance by 1 degrees Celsius
what does specific heat capacity depend on
- type of material
- mass of material
- temperature rise
what’s the equation for specific heat capacity
Energy (J) = mass (kg) x specific heat capacity (J/kgC) x change in temp (C)
how can you find SHC of a metal block
- check start temp of block
- heat the block with immersion heater + turn off
- check new temp - change in temp
- check joules supplied - Energy
- weigh block - mass
- use equation to find SHC
what is specific laten heat of fusion
- changes between solid + liquid
what is specific latent heat of vaporisation
- changes between liquid + gas
what is specific laten heat
- the amount of energy needed to be gained / lost to change state of 1kg of the substance
why is SL HOV a lot greater than SL HOF
- because the difference between bond energies in solid + liquid is much less than the difference in bond energies between liquid + gas
what is the equation for specific laten heat
Energy (J) = mass (kg) x latent heat (J/Kg)
why doesn’t temperature increase during a phase change e.g. when a solid melting or liquid is boiling
- because the energy is used to break the intermolecular bonds between the atoms
how can you work out SLH of water
- melt sample of ice with immersion heater
- use collected ice water + measure mass
- find how many joules were used
- put into equation
what is pressure
- force per unit area
pressure (Pa) or (N/m2) = force (N) / area (m2)
describe the motion of molecules in a gas
- they are in constant random motion
what is the relationship between pressure + volume
- pressure and volume are inversely proportional (Boyles law)
> as volume doubles, pressure halves
> as volume halves, pressure doubles
how do gases exert pressure
- particles in gases move randomly and occasionally collide with the container walls
> each collision exerts a force at right angles on the wall
> the total force of thee collisions divided by the container surface area is pressure
how does temperature affect gas pressure
- as the temperature of a gas increases, the gas particles gain more kinetic energy and so they move around more + faster
> this results in more frequent collisions with the container wall so they produce a larger force over an certain area - which produces a bigger pressure
how can doing work on a gas increase its temperature
- when using a bicycle pump you can notice the valve getting hotter
> when you apply force to the pump + move it in you do work on the gas + it gets hotter
> the average speed of the particles increase because their kinetic speed increases when they collide with the moving piston + so the temperature gets higher
what is the equation for pressure and volume
constant = pressure x volume
why does atmospheric pressure decrease as you go higher up
- there are less gas particles pressing from above
what is the pressure on the surface of the earth
- 1 atmosphere / 101 kPa (101,000 Pa)
what is a barometer used to measure
air pressure
what does water exert + how
- liquid pressure
- water molecules move and collide with each other and the container and so exert a pressure
what happens to liquid pressure as you go deeper
- the deeper you go, the more liquid their is above so pressure increases
what happens to pressure in liquids of different densities
- the pressure at a particular depth will always be greater in the denser liquid
> this is because in the denser liquid there is a greater weight of liquid pushing down
what is the equation for liquid pressure
- pressure (Pa) = height (m) x density (kg/m*3) x gravitational field strength (N/kg)
- pressure = height x density x gravitational field strength
anything that is floating must have an ____
- upwards force on it to balance its weight
> upthrust
how do objects float + sink
- float = upthrust from water equals weight of object
- sink = if weight is greater than upthrust object sinks
what does the size of upthrust depend on
- weight of water displaced
what will happen to an object that is less dense than the liquid it’s being placed in
- it will float
(pressure at bottom x area at bottom) - (pressure at top x area at top) =
weight
