c1 atoms, elements and compounds Flashcards
what is an atom?
the smallest particle of a substance to exist
what are compounds?
Compounds are formed from elements by chemical reactions.
Chemical reactions always involve the formation of one or more
new substances
how can you separate a compound?
Compounds
can only be separated into elements by chemical reactions
what is a mixture?
A mixture consists of two or more elements or compounds not
chemically combined together
a feature of mixtures?
they have properties of the substances within the mixture
a feature of compounds?
they have different properties to the substances within the compound
how can mixtures be seperated?
1) filtration
2) chromatography
3) distillation
4) fractional distillation
5) crystallisation
describe the process of filtration
1) make cone shape with filter paper
2) place it upside down in a beaker
3) pour solution (slowly) into the cone
- insoluble particles will not pass through the filter paper, only dissolved ions will
describe the process of chromatography
1) at the near bottom of chromatography paper draw a straight line of pencil (pencil doesnt dissolve with the ink)
2) place a small dot of the ink you want to separate on the line
3) pour warm water in a beaker and put the chromatography paper inside, making sure the level of the water is just beneath the line
describe the process of distillation
1) pour liquid into the distilling flask and heat with a bunsen burner until the bp of one of the substances
2) one substance will then evaporate and travel to the condensing tube which will turn it back to liquid
3) the liquid will then pour out into an empty beaker
describe the process of fractional distillation
1) heat the substances in the mixture
2) they will evaporate at their bp, and travel up the factional tube
3) they will condense back as it gets cooler as they travel up and 4) the substances with the lowest bp will continue to travel up, go into the condensing rube and return to liquid state
5) change the beaker and repeat while heating the substances in the mixture at a higher temp
describe the process of crystallisation
1) pour solution in an evaporating basin
2) warm the basin by placing it over a hot water bath OR very weak flame
3) stop heating after crystals form on the edges of the basin
4) keep stored in a cool and dry area
timeline of the development of the atom?
1) belief that atoms where tiny spheres which could not be divided, however this changed with the discovery of electrons
2) J.J Thompson discovered the ‘plum pudding’ model
3) scientists carried out the ‘alpha scattering experiment’
4) from the conclusions drawn from the ASE, the nuclear model was introduced
5) Bohr discovered that electrons orbit the nucleus at specific distances
6) chadwick discovered neutrons
describe the alpha scattering experiment
1) scientists took a piece of gold (gold was used specifically because it could be hammered into a very thin sheet, just a couple atoms thick)
2) scientists then fired tiny (positive) alpha particles at the sheet
- most particles passed straight through the atoms, implying that the atom was mainly made up of space
- sometimes it deflected direction as it passed through, implying that there has to be a positive charge in the centre of the atom
- sometimes it bounced straight back, implying that the centre is dense (we now call this, the nucleus)
sizes of the atom
radius= 0.1nm (1x10^-10)
radius of nucleus= 1x10^-14)
protons and neutrons= 1
electrons= very small