particle model of matter - states of matter Flashcards
properties of a solid
- particles are very close together
- arranged in a regular pattern
- particles in a solid vibrate but do not move from place to place
- high density
properties of a liquid
- particles close together
- not arranged in a regular pattern
- particles can move around each other
properties of a gas
- particles very far apart
- move very rapidly
- not arranged in any pattern
Describe Rutherford’s alpha particle experiment
Most alpha particles passed straight through the foil.
This suggested that most of the atom is made up of empty space.
However, some particles bounced back towards the source.
The large deflections suggested that some positively charged mass in the atom was repelling the particles.
This led to the model of the atom with negatively charged electrons orbiting a positively charged nucleus.
Describe JJ Thomson’s plum pudding discovery
In 1897, an English physicist called J. J. Thomson discovered electrons.
He modelled the atom as a ‘plum pudding’ - a ball of positive charge (dough), with negatively charged electrons (currants) mixed in with the ‘dough’.
discovery of protons
In 1909, Ernest Rutherford discovered that alpha particles could bounce back off atoms.
He concluded that an atom’s mass is concentrated in the atom’s centre. This was called the “nucleus” and it contained positively charged particles called protons
what is density
The density of a material tells us the mass for a given volume
density equation
density = mass / volume
why do solids usually have a high density
because their particles are packed closely together, solids have a lot of mass for their volume
why do liquids usually have a high density
because their particles are packed fairly closely together
why do gases have a low density
because the particles are far apart, so gases only have a small mass for their volume
in terms of density, why would an object float
because the objects density is less then the density of the fluid
properties of change of state reaction
- reversible reaction
- physical change
- mass is conserved
when does a liquid boil
when the particles have enough energy to completely escape the forces between them
describe melting ( solid to liquid )
If we heat a solid, the solid particles vibrate more energetically, as we increase the internal energy, until they have enough energy to overcome the forces between them. This is when the solid melts (becomes a liquid).
