Atoms have a radius of
0.1 nanometers (1 x 10-10 m)
The nucleus of an atom has a radius of
1 x 10-14 metres (1/10000 of the radius of an atom)
Atoms don’t have an overall charge as it has equal protons and electrons
Name the region where most of the mass of the atoms is concentrated
What is the relative charge of an electron?
Name the particles in the nucleus and give their relative charges
Neutrons (0) protons (+1)
Number on top
Atoms are the
Smallest part of an element that can exist
What are isotopes
Have the same number of protons but a different number of neutrons
How to work out the relative atomic mass
Sum of (isotope abundance x isotope mass number)/ 100
What is a compound?
Two or more elements chemically combined (in fixed proportions)
How to work out the number of atoms in a compound
The sum of All elements involved
How many atoms in C2H4
If C2H4 and H2 react to form C2H6, has a new compound been made?
Yes because the atoms in C2H6 are in different proportions to the atoms in the previous
What is a reactant
Everything on the left
What is a product
Everything on the right
Balance Na + Cl = NaCl
2Na + Cl2 = 2NaCl
Balance NH2 + O2 = NO + H2O
4NH3 + 5O2 = 4NO + 6H2O
What is a mixture
Consists of two or more elements or compounds that aren’t chemically combined together
Outline the procedure for setting up a chromatography experiment
1) Draw a line in pencil near the bottom of a piece of chromatography paper.
2) Place a spot of ink on the pencil line. Pour a shallow layer of water or solvent into a beaker. 3) Place the chromatography paper into the container. The water should be below the pencil line and the ink spots.
4) Place a lid in the container and wait for the solvent to rise to the top of the paper.
5) Remove the paper from the container when the solvent had risen close to the top of the paper.
Explain the results of a chromatography experiment
Count the spots that the dyes have made and state how many dyes were involved in the specific spots. State which are mixtures. State which dyes contain at least one of the same dyes (no clue what that meant but there you go)
What is filtration?
Filtration deprecated insoluble solids from liquids
Can’t be dissolved in the liquid
Pour the solution into an evaporating dish.
Slowly heat a solution.
Solvent will evaporate.
Solution gets more concentrated.
Crystals will start to form.
Keep heating the evaporating disk until all you have left are dry crystals.
Two ways to separate soluble solids from solutions
Evaporation and crystallisation
Pour the solution into an evaporating dish and gently heat the solution.
Some of the solvent will evaporate and the solution will get more concentrated.
Once some of the solvent has evaporated or when you see crystal starter form (the point of crystallisation), remove the dish from the heat and leave the solution to cool.
Salt will form crystals as it becomes insoluble in the cold highly concentrated solution.
Filter the crystals out of the solution and leave them in a warm place to dry.
You could use a drying oven or a desiccator.
Why can’t we use evaporation all the time?
You can only use it if the salt doesn’t decompose when it’s heated
What can we use to separate rock salt
Filtration or crystallisation
What is rock salt?
Rock salt is simply a mixture of salt and sand (grit)
Salt and sand are both…
How to separate rock salt
Grind mixture to make salt crystals small so will dissolve easily
Put mixture in water and stir.
Salt dissolves sand won’t
Filter the mixture Salt passes through as if it’s part of the solution and sand gets left on the filter paper
Evaporate the water from the salt so that it forms dry crystals.
What is simple distillation?
Simple distillation is used for separate out a liquid from a solution.
How to perform simple distillation? (Seawater)
Solution heated. Part of the solution with the lowest boiling point evaporates first.
Vapour cooled, condensed and collected.
The rest of the solution is left behind in the flask.
simple distillation used to get pure water from seawater.
Water evaporates and is condensed and collected.
Only salt left in the flask.
What is the problem with simple distillation?
You can only use it to separate things with very different boiling points
What is fractional distillation?
If you have a mixture of liquids you can separate it using fractional distillation .
How to perform fractional distillation?
Mixture in a flask with a fractional column on top. Then heat.
The different liquids all have different boiling points so they will evaporate at different temperatures.
Liquid with lowest boiling point evaporates first .
When the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column.
Liquids with boiling points might also start to evaporate. Column is cooler near the top so liquid will return to the bottom.
Who was John Dalton?
At the start of the 19th century, he described atoms as solid spheres, and said that different spheres made up the different elements.
Who was J J Thompson?
In 1897, he concluded from his experiments that atoms weren’t solid spheres. His measurements of charge and mass showed that an atom must contain even smaller, negatively charged particles, electrons. The new theory was known as the Plum Pudding Model.
What is the Plum Pudding Model?
Showed an atom as a ball of positive charge with negatively charges particles scattered around in it.