C1 Flashcards
How many elements are there?
Around 100
Define element
In an element, all the atoms are the same.
Define compound
Contains 2 or more different elements chemically combined in fixed proportions.
How to separate a compound?
Use a chemical reaction.
Define mixture
Different elements or compounds not chemically combined together.
How to separate a mixture
Use a physical separation technique.
Define molecule
Has any elements chemically combined (even if they are the same element). Some molecules can be compunds too.
4 separation techniques
Filtration, chromatography, crystallisation, distillation
Function of filtration
Used to separate an insoluble (will not dissolve) solid from a liquid. (s) and (l)
How to do filtration?
Put filter paper in a filter tunnel and pour the mixture through it. The liquid passes through the tiny pores in the filter paper and the solid is trapped in the filter paper.
Function crystallisation
Used to separate a soluble solid from a liquid. (aq) and (l)
How to do crystallisation?
If you leave the solution for a few days or gently heat the water, then the liquid will evaporate. You have to make sure heating will not affect the chemical that is being crystallised. This will leave behind crystals of the solid. (aq) to (s).
Function of simple distillation
Used to separate a liquid from a solid if we want to keep the liquid,
Function of fractional distillation
Used to separate 2 different liquids, which must have different boiling points. (l) and (l)
How to do simple distillation?
- Evaporate the liquid by heating. 2. Condense the vapour by cooling.
How to do fractional distillation?
- Evaporate mixture by heating. The one with the lower boiling point will evaporate more easily. 2. The liquid with the lowest boiling point will evaporate first and it will reach the top of the column and condense through the condenser. 3. When the first liquid has been collected, you raise the temperature until the next one reaches the top.
How to do fractional distillation?
- Evaporate mixture by heating. The one with the lower boiling point will evaporate more easily. 2. The liquid with the lowest boiling point will evaporate first and it will reach the top of the column and condense through the condenser. 3. When the first liquid has been collected, you raise the temperature until the next one reaches the top.
Function of paper chromatography
Used to seaparate substances based on their different solubilities.
How to do paper chomatography?
- Draw a pencil line near the bottom of chromatography paper. 2. Put dots of each colour on the pencil line. 3. Place the bottom of the paper into a solvent (a liquid that dissolve substances). 4. The solvent makes its way up the paper and dissolves the ink in the dots.
Define stationary phase in paper chromatography
Does not move - paper
Define mobile phase in paper chromatography
Does move - solvent
What happened in 1897?
J. J. Thomson concluded that atoms were not tiny spheres and contained tiny negative particles and called them electrons and had an internal structure. The plum pudding model showed the atom as a ball of positive charge with electrons stuck in it.
What happened in 1909?
Ernest Rutherford conducted the alpha particle scattering experiment. They fired positively charged alpha particles at an extremely thin sheet of gold. Most of the particles passed straight through without changing direction - atoms were mainly empty space. Some were deflected - the centre had a positive charge. Some bounced straight back - the centre had a great deal of mass - known now as the nucleus. Came up with the nuclear model.
What did Neils Bohr discover?
Electrons orbit the nucleus at specific distances. Orbits are now called energy levels or shells. Positive charge is due to positive particles called protons. Updated nuclear model.
