SC1-2 Flashcards
What are the 3 states of matter?
Gas
Liquid
Solid
What are the properties of a solid?
- They have strong forces of attraction between particles, which hold them in a fixed positions in a regular lattice arrangement.
- The particles don’t move from their positions so all solids keep a definite shape and volume.
- The particles don’t have much energy.
- They hardly move at all - they can only vibrate about their fixed positions. The hotter the solid becomes, the more they vibrate, (expand slightly).
What are the properties of a liquid?
- There is some force of attraction between the particles. They’re free to move past each other, but they do tend to stick together.
- They don’t keep a definite shape and will flow to fill the bottom of a container. They do keep the same volume.
- In liquid state the particles have more energy than in solid state.
- The particles are constantly moving with random motion. The hotter the liquid gets, the faster they move. (Causes it to expand slightly).
What are the properties of a gas?
- Pretty much no force of attraction between the particles - they’re free to move. They travel in straight lines and only interact when they collide.
- They don’t keep a definite shape or volume and will always fill any container.
- In gas state particles have more energy than in solid or liquid state.
- Particles are constantly moving with random motion. The hotter it gets the faster they move. Gases either expand or their pressure increases when heated.
What are the names for the changes of state?
Solid - liquid = melting
Liquid - solid = freezing
Liquid - gas = evaporating
Gas - liquid = condensing
Solid - gas = subliming
What do pure substances made of?
Completely made up of a single element or compound.
What is a mixture?
When you’ve got more than one compound present, or different elements that aren’t part of a single compound
What’s a compound?
Different elements bonded together.
What’s an element?
Atoms are identical.
How can you test for purity?
Using melting points.
How does the test for purity work?
- Every pure substance has a specific, sharp melting point and boiling point. (E.g - water freezes at 0 and boils at 100).
- You can use this to test the purity of a sample of a substance, by comparing the actual meting point of the sample to the expected value.
What does simple distillation do?
Separating out a liquid from a solution.
What’s the method for a simple distillation, when getting pure water from seawater?
- Pour your sample of seawater into the distillation flask.
- Set up the apparatus. Connect the bottom end of the condenser to a cold tap using rubber tubing. Run cold water through the condenser to keep it cool.
- Gradually heat the flask. The part of the solution that has the lowest boiling point will evaporate - in this case the water.
- The water vapour passes into the condenser where it cools and condenses. It then flows into the beaker where it is collected.
- Eventually there will be just salt left tin the flask.
What’s the problem with simple distillation?
Its that you can only use it to separate things with very different boiling points.
If you have a mixture with similar boiling points, you need another method such as fractional distillation.
What does filtration do?
Its used to separate an insoluble solid from a liquid.
How do you carry out a filtration?
Put some filter paper into a funnel and pour your mixture into it. The liquid part of the mixture runs through the paper, leaving behind the solid residue.
What does crystallisation do?
Separates a soluble liquid from a solution.
How do you carry out crystallisation?
- Pour the solution into an evaporating dish and gently heat the solution. Some of the water will evaporate and the solution will get more concentrated.
- Once some of the water has evaporated, or when you see crystals start to form, remove the dish form the heat and leave the solution to cool.
- The salt should start to 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.
What is chromatography?
A method used to separate a mixture of soluble substances and identify them.
What are the two phases of chromatography?
Mobile phase.
Stationary phase.
What is the mobile phase?
Where the molecules can move. This is always a liquid or gas.
What is the stationary phase?
Where the molecules cant move. This can be a solid or a really thick liquid.
What is the method for paper chromatography?
- Draw a line near the bottom of the paper. (Use pencil as its insoluble).
- Put a small spot of ink form each pen on your line.
- Pour some water into the beaker to a depth of about 1cm, and lower the chromatography paper into the beaker so that the bottom of the paper is int he water but the water isn’t touching the ink.
- Leave the paper in the beaker until the water reaches near the top of the paper.
- Take the paper out and immediately use a pencil to mark the location of the solvent front before it evaporates. Leave it to dry.
What is the baseline?
The line near the bottom of the paper.
