Relative atomic mass is the average weight of an atom of an element. There is variation in the weight due to the fact that there are different isotopes with in an element. (Different isotopes have different weights due to less or more neutrons.)
It is calculated like this:
(% of isotope x its mass) + (% of isotope x its mass) / 100
e.g for chlorine
75% of all chlorine has a mass of 35. 25% of all chlorine has a mass of 37.
Chromatography paper is placed in a solvent, the different compounds will travel at different speeds (due to the size of their particles.) Rf values The Rf value is calculate by Distance moved by compound divided by Distance moved by solvent. Chromatogram The shape on the chromatogram can be compared with that of known substances and where they match they are the same substance.
This consists of a barrier which one component f a mixture can pass through but the other is caught by.
e.g water goes through filter paper, rocks are caught by it.
One substance is evaporated off.
e.g salt water is heated to 100 degrees; water evaporates off (it rises and the goes down into the condenser where it is cooled back into water), the salt is left in the original flask. See diagram.
The mixture is evaporated and rises up the tube.
Different substances have different boiling points and so will condense at different temperatures; as the mixture travels up the tube the temperature decreases, substances begin to condense at different places (due to the change in temperature) and are collected. This separates the mixture into its different parts.
A solution is warmed allowing the solvent to evaporate, the solution is now left to cool and will form crystals.
chromatography paper is placed in a substance, the different components of the substance will travel at different speeds (due to the size of their particles.)
Dilution: a substance is put in a solvent to reduce its concentration
Diffusion: The movement of particles from an area of high concentration to an area of low concentration
Experiment 1, Diffusion
Hydrochloric acid is placed at one end of a tube, ammonia solution at the other.
Where they meet a ring of ammonium chloride appears.
The diagram shows it is closer to the HCL end.
From this we can tell that ammonia must have travelled faster, as it got further in the time. Lighter particles travel faster- so we can tell that ammonia is a lighter gas.
Experiment 2, Dilution
Put a coloured substance in a solvent e.g food colouring in water.
You can see that over time the colour levels out but is weaker than the original colour- this is dilution.
Dilution at different temperatures: more heat; means more energy; means more movement; so the particles can move to different areas more quickly. So applying heat decreases the amount of time taken for the coloured substance to be fully diluted.