States of Matter and Mixtures (Changes of State (A solid can become a…
States of Matter and Mixtures
States of Matter
Strong forces of attraction between the particles which hold them in a fixed position
Particles don't move
Not a lot of energy
Can only vibrate
Free moving but stick together, have some force of attraction
Don't stay in shape, they flow. Do keep same volume
Have some energy
Almost no force of attraction. Travel in straight line. Only interact when they collide
Don't keep shape or volume but will always fill a container
Has a lot of energy
Consistant movement with random motion
Changes of State
A solid can become a liquid through melting
A solid can become a gas by subliming
A liquid can become a gas through evporation
A gas can become a liquid through condensing
A liquid can become a solid through freezing
Chemical changes in reactions are hard to reversew
Made up of one single element or compund
For example air is chemically impure
Testing for purity
Every pure substance has a specific melting point and boiling point.
You can use this to test the purity of a sample of a substance, by comparing the actual melting point of the sample to the expected value.
If a substance is a mixture then it will melt gradually over a range of temperatures, rather than having a sharp melting point, like a pure substance.
Impure substances will melt over a range of temperatures, because they are effectively mixtures.
To measure the melting point of a substance, you can use melting point apparatus. This is a piece of kit that allows you to heat up a small sample of a solid very slowly, so you can observe and record the exact temperature that it melts at.
Simple distillation is used to separate liquids
Pour your sample of sea water into a distillation flask
Keep the condenser cool by running cold water through it
Gradually heat the distillation flask. The part of the solution that has the lowest boiling point will evaporate - in this case its the water
The water vapor passes into the condenser where it cools and condenses (turns back into a liquid) It then flows into the beaker where it is collected
Eventually you'll end up being left with just salt in the flask
Can only be used to separate things with very different boiling points
The liquid with the lowest boiling 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 higher boiling points might also start to evaporate. But the column is cooler towards the top, so they will only get part of the way up before condensing and running back down towards the flask
Gradually heat the flask. The different liquids will all have different boiling points - so they will evaporate at different temperatures
When the first liquid has been collected, raise the temperature until the next one reaches the top
Put your mixture in a flask. Attach a fractional column and condenser
The components in the mixture separate out as the mobile phase
This happens because each of the chemicals in a mixture will spend different amounts of time dissolved in the mobile phase and stuck to the stationary phase
How fast a chemical moves through the stationary phase depends on how it distributes itself between two phases
Draw a pencil line near the bottom of the paper - this is the baseline. Put a spot of mixture to be separated on the line
Put some of the solvent into a beaker. Dip the bottom of the paper (but not the spot) into the solvent
Put a spot glass on top of the beaker to stop the solvent evaporating
Remove the paper from the beaker before the solvent reaches the top. mark the distance in pencil.
The solvent will start to move up the paper. When the chemicals in the the mixture dissolves in the solvent, they will move up the paper too.
You will see the different chemicals in the sample separate out forming spots at different places on the paper.
Rf value = distance traveled by solute / distance traveled by solvent