CHEMISTRY REVISION GUIDE Flashcards
(31 cards)
what does the state depend on?
It depends on the forces of attraction between the particles. These forces depend on the material, temperature and pressure.
Describe solids
In solids, there are…
- strong forces of attraction holding it together in a fixed regular lattice arangement
- definite shape and volume
- their particles vibrate in their positions
- when heated, their particles vibrate faster and allow the to expand
describe liquids
in liquids, there are…
- weak forces of attraction between the the particles
- randomly arranged (but they tend to stay closely together.
- the dont have a fixed shape but do have a fixed volume.
- their particles are constantly moving but when heated the expand
describe gases …
in gases, there are…
- very weak forces of attraction
- move far apart from each other
- travel in straight lines between collisions
- constantly moving randomly
- don’t have definite shape of volume (they fill any container)
- when heated their particles move faster which means they expand or their pressure increases
what is solid -> liquid
melting
what is liquid -> gas
evaporating
what is gas -> liquid
condensing
what is liquid -> solid
condensing
what is solid -> gas
subliming
define diffusion
the gradual net movement of particles moving from areas of high concentration to areas of low concentration until a uniform concentration is achieved
what experiment is used to demonstrate diffusion through liquids
1) potassium manganate (vii) + water
what are your observations in the experiment to test diffusion in liquids.
1) the potassium manganate is placed at the bottom of the beaker
2) the particles are slowly diffusing out a,ong the particles in the water
3) it’s the random motion of particles in the liquid which cause it to eventually spread out.
(if you were to add more water, the particles could spread out even further making it less purple . This is called dilution.)
what are the 2experiments to show diffusion between gases
ammonia + hydrogen chloride
and
bromine gas and air
describe what is observed in the diffusion experiment- ammonia and hydrogen chloride
1) the aqueous ammonia (cotton wool soaked in NH3) gives off ammonia gas and the hydrochloric acid gives off hydrogen chloride gas.
2) the NH3 gas diffuses from one end of the tube and the HCl on the other
3) A white ring of ammonium chloride will form at the end closer to HCl as is diffuses faster (ammonia is lighter)
describe what you observe in the experiment: bro kng gas and air
1) fill a jar full of bromine gas and the other with air (separated by a glass plate)
2) remove and watch the diffusion take place
3) the random movement of particles mean it will completely fill the jar.
key features of the nucleus
contains protons and neutrons
has positive charge (because of protons)
almost its entire mass is concentrated here
describe the key feature of electrons
they move around the nucleus in energy levels, called shells
negatively charged
their size of their orbits determines the size of the atom
the has virtually no mass
protons :
relative mass and charge
they are heavy with a R.M of 1
positively charged (+1)
neutrons:
relative mass and charge
heavy - rm 1
no charge (0)
electrons:
relative mass and charge
tiny - 1/2000
negatively charged (-1)
describe the neutral charge of atoms
they have no charge overall. this means that the charge on the electrons is the same size as the protons. the number of electrons will be equal to the number of protons . if protons are added or removed, the atom will become and ion
a
X
b
a=mass number (p+n)
b=atomic number (p)
X=atom
describe molecules
molecules are groups of atoms e.g. O2
atoms can form together to make molecules, some can be made from one or more than one element e.g. H2O. molecules are held together by covalent bonds
definition of an element
An element consists of one type of atom. They cannot be broken down into simpler substances by chemical means (heat or electricity). An example is O2- elements can also be molecules.
