C1 - Particles Flashcards
What are the 3 states of matter
Solid
Liquid
Gas
what is the particle model
- the particle model describes how particles are arranged and how they move in solids, liquids and gases
describe the arrangement + movement of particles in solids
- particles are packed very close together in a regular arrangement
- particles vibrate in fixed positions
describe the arrangement + movement of particles in liquids
- particles are close together but able to move past each other (random arrangement)
- particles vibrate + move around each other
describe the arrangement + movement of particles in gases
- particles are far apart with no regular arrangement (random arrangement)
- particles vibrate + move freely at high speeds
how do the relative energies of particles in the 3 states of matter compare
- particles in solids have the least amount of energy
- particles in gas have most energy
what are physical changes
- when a substance changes state or shape
> no new substances are made
> many physical changes can be reversed
what are chemical changes
- when a change produces one or more new substances
> many chemical changes are difficult or impossible to reverse
what happens to particles when a substance changes state
- they stay the same, but their arrangement and movement change
what happens to particles during chemical changes
- particles break up + join together in different ways
> that’s why new substances are made
what is the smallest particle that makes up a substance
atoms
what are forces between particles called
- electrostatic forces of attraction between positive + negative charges
> the forces become weaker the further apart the particles are
what are limitations of the particle model
- doesn’t take into account:
> the forces between particles
> the size of particles
> the space between particles
describe what happens in terms of particles when solids are heated + melts into liquid
- when heated, particles absorb thermal energy + convert it into kinetic energy
- the particles in the solid vibrate more, causing the solid to expand until the structure breaks and the solid turns into a liquid
describe what happens in terms of particles when a liquid is heated and evaporates into a gas
- when heated, the particles in a liquid expand
- some particles on the surface gain sufficient energy to overcome the intermolecular forces and evaporate
- at the boiling point, all of the liquid particles gain enough energy to evaporate
why do solids, liquids and gases expand when heated
- when heated, the molecules vibrate faster
> this causes the space between atoms to increase
what are elements + compiunds
- elements are substances made up of one type of atom
- compounds are made up of atoms of different elements
what is a molecule
- a molecule is made from two or more atoms joined together by attractive forces called chemical bonds
what are the relative mass + relative charges of the subatomic particles
- proton = 1 = +1
- neutron = 1 = 0
- electron = 1/2000 = -1
what are the subatomic particles in the atom
- protons
- neutrons
- electrons
what is the atomic number of an element
- the number of protons
> and also electrons as every atom has equal num of protons + electrons
what is the mass number of an element
- total number of protons + neutrons
- mass number = num of protons (atomic number) + num of neutrons
what are isotopes
- atoms with the same number of protons + electrons but diff number of neutrons
> they have same atomic number but diff mass number
why do isotopes of an element have identical chemical properties
- because the have the same number of electrons
what are ions
- charged particles
when are ions formed
- when atoms, or groups of atoms, lose/gain electrons
who describe atoms as ‘solid sphere’
John Dalton
what was Dalton’s theory
- that all matter is made from atoms
- all atoms of an element are the same
- different elements contain different types of atoms
> his model showed no subatomic mass - each atom was essentially a solid sphere of a certain mass
what discovery caused Dalton’s model of an atom to change
- the discovery of subatomic particles
what did JJ Thomson discover + how
- the electron in an experiment which polluted cathode rays
- he proposed the plum pudding model:
> atom has a weak positive sphere with negative electrons embedded into it
> atoms are neutral overall
what experiment did Rutherford (alongside Geiger and Marsden) carry out
- gold foil experiment:
>fired a source of alpha particles at thin gold foil
> they found that most particles went through
> but some were slightly deflected
> some even came straight back
what did Rutherford conclude from his gold foil experiment
- that the atom has a positively charged nucleus containing most of its mass which is very small and dense as alpha particles could pass through atom
- around the nucleus must be negative electrons
> most of the atom is empty space
what did Bohr find out + how
- that electrons orbit on shells
> after realising that electrons would be attracted to the positive nucleus and that the atom would collapse he showed electrons to occupy fixed energy levels / shells
who founded the existence of neutrons
- James Chadwick
compare the sizes of the nuclear radius and the atomic radius
- nuclear radius is much smaller than atomic radius
compare the typical size of atoms and small molecules
- atoms and small molecules are incredibly small
> small molecules are larger than atoms because they are mode of atoms - the typical atomic radii and bond length are in the order of 10-10m
what is the size of nanoparticles
- 1nm to 100nm in size
