Studied by 9 people
What was j.j Thomsons thoery of the atom
plum pudding model
discovered electrons which are dotted around inside spheres of positive charge
what was rutherfords theory if the atom
atoms have a central, positively charged nucleus with most of the mass
nucleus surrounded by cloud of negative electrons so most of atom is empty space
what experiment did rutherford and marsden conduct
aimed beams of positively charged alpha particles at very thin gold foil.
According to the plum pudding model, these particles should have passed straight through. However, many of them changed direction instead.
this meant it had to have a small positively charged nucleus
whats was bohrs model of the atom
a problem with Rutherford's model - the electrons would eventually fall into the nucleus because they are negatively charged and so attracted to the positive nucleus.
Niels Bohr improved Rutherford's model. Using mathematical ideas, he showed that electrons occupy shells around the nucleus.
how big is the diameter of an atom
1 x 10 to the power of -10 m
what is an atom
a positively charged nucleus surrounded by negatively charged electrons, with the nucleus size being much smaller than that of the atom and with the most mass in the nucleus
what does the nucleus of an atom contain
protons and nutreons ( so positively charged)
what is density
a measure of ‘ compactness’
Mass per unit volume
what is the equation for density
denisty (kg/m 3) = mass (kg)/ volume (m2)
when a substance changes state, does the mass change and why
no because the mass of a substance is the mass of its particles and the particles arent changing they’re just being rearranged
when a substance changes shape, does the density change and why
yes as when a substance changes state its volume changes as the partciles are closer together in a solid and further away in a liquid + gas.
denisty = mass/ volume so density must change too
solids are most dense and gasses are least
how do you measure the denisty of a solid cuboid
find out mass by weighing it
for volume do length x width x height
mass / volume
how do you find the density of an object
find out mass by weighing it
for volume use a eurika beaker
mass / volume
how do you use a eurika beaker to find the volume of an object
fill eurika beaker so water level is just under the spout
place measuring cylinder under spout and put object in water
the volume of water collected in the measuring cyclinder is the volume of the object
what are the characteristics of a solid
strong forces of attraction hold particles close together in a fixed , regular arrangement
only vibrate as not much energy in kinetic energy stores
why is a solid denser than gas
because the particles are tightly packed in a regular structure whereas in a gas the particles are spread out
what are the characteristics of a liquid
weaker forces of attraction between particles
particles can flow over each other to form irregular arrangement
more energy in kinetic energy stores
what are the characteristics of a gas
almost no forces of attraction between particles and are free to move
particles travel in random directions at high speeds
have lots of energy in kinetic energy stores
why do solids melt into liquids
because as particles vibrate more, some of the forces of attraction between them weaken causing the solid to melt into a liquid
how does a liquid become a gas
adding more heat energy breaks the bonds between the atoms completely
whats it called when a solid turns into a liquid
melting
whats it called when a liquid turns into a solid
freezing
whats it called when a liquid turns into a gas
evaporating
whats it called when a gas turns into a liquid
condensing
whats it called when a gas turns into a solid/ solid turns into a gas
sublimating
what 2 things can heating a substance do
raise its temperature
change the state of the substance
What's specific heat capacity?
the energy required to raise the temperature of 1kg of a substance by 1 degree
what does a low heat capacity mean
it heats up quickly
what does a high heat capacity mean
it takes longer to get hot
whats the equation for specific heat capacity
Energy = mass x specific heat capacity x temp change
whats specific latent heat
the amount of energy needed to change the state of 1 kg of material without changing its temperature
whats the equation for specific latent heat
energy = mass x specific latent heat
whats the equation for pressure
pressure = force/ area
how does the temperature make the pressure go up
high temperatures mean particles have more heat energy and collide with the sides of the container more
why does decrease in volume make the pressure go up
particles have less room to move meaning they collide with the container more frequently
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