Chem Paper 1
Name 5 methods of separating mixtures
- Chromotography
- Filtration
- Crystalisation
- Simple distillation
- Fractional distillation
Describe how to carry out paper chromotography
1. Draw a line near the bottom of a sheet of filter paper using a pencil
2. Place a small about of ink on the line
3. Put the sheet upright in a beaker of solvent
4.Placea lid on top of the container to stop the solvent evaporating
5. The solvent will seep up the paper, carrying the ink with it
6. The different dyes in the ink will move up the paper at different rates
7. Take the paper out and draw a pencil line on the solvent front
8. The end result is a pattern of spots called a chromatogram
Describe how to carry out filtration
1. Fold a piece of filter paper into a cone
2. Place the filter paper point down into a filter tunnel that's sitting in the neck of a container
3. Pour the mixture containing the insoluble solid into the funnel making sure none of the liquid goes down te side of the paper
4. The liquid will pass through the filter paper but the solid wont
Describe how to carry out evaporation
1. Pour the solution into an evaporating dish
2. Place the evaporating dish on top of a tripod and gauze and place a Bunsen burner underneath
3. Slowly heat the solution
4. The solvent will evaporate and the solution will geet more concentrated and eventually a solid will start to form
5. Keep heating the evaporating dish until all you have left is a dry solid
Describe how to carry out crystallisation
1. Place an evaporating dish on top of a tripod with a gauze mat and place a Bunsen burner underneath
2. Pour the solution into the evaporating dish and gently heat it - some of the solvent will evaporate and the solution will get more concentrated
3. When you see crystals starting to form remove the dish from the heat and leave to cool
4. The salt will start to form crystals as it becomes insoluble. The longer the solution is left to cool, the larger the crystals will be
5. Filter the crystals out the solution and leave them in a warm place to dry
Describe how to carry out simple distillation
1. Set up the equipment and heat the mixture
2. The component with the lowest boiling point evaporates
3. As the vapour rises it passes into the condenser where its cooled, condenses and is collected into the container below
4. Components of the mixture with higher boiling points are left behind in the flask
Describe how to carry out fractional distillation
1. Set up the equipment and place the mixture in a flask and attach a fractionating column on top and heat it
2. The liquids will have different boiling points so will evaporate at different rates
3. When the temp on the thermometer matches the temp of the boiling point of the liquid, its vapour has reached the top of the columm and is passed to the condenser. It will then cool and condense and the pure liquid can be collected
4. When the first liquid has been collected, you raise the temp to the next lowest boiling point of the liquids in the mixture
How do you determine the number of protons, electrons and neutrons in an atom?
Protons: Atomic number (bottom number)
Electons: Same as protons
Neutrons: Mass number (top number) - Atomic number (bottom number)
Give 3 properties of Group 1 metals (alkali metals)
- One electron in there outer shell
- Very reactive
- Low density
Explain reactivity in group 1 metals (alkali metals)
- Reactivity increases as you go down the group
- Because group 1 metals react by loosing the single electron in their outer shell
- As you go down the group, the outer electron gets further from the nucleus so the outer electron is more easily lost because the attraction decreases
Explain the melting and boiling points in group 1 metals
decrease as you go down the group
Give 3 properties of metals
- They're strong
- They're great conductors of heat and electricity
- They have high melting and boiling points
Give 3 properties of non metals
- More brittle than metals
- Don't conduct electricity
- Lower density than metals
What do alkali metals (group 1) form when reacted with water and give 3 observations
alkali metal + water = metal hydroxide + hydrogen
- They react vigourously
- Bubbles of hydrogen gas
- Squeaky pop
What do alkali metals form when reacted with chlorine?
alkali metal + chlorine = metal chloride
Equation for percentage atom economy
total mass of desired product divided by the total mass of all reactants multiplied by 100
Why do alkaline batteries eventually stop working?
a reactant is used up
Why can alkaline batteries not be recharged?
the reaction is not reversible
Describe the plum pudding model
A ball of positive charge with negative electrons embedded in it
Explain why hydrogen chloride is a gas at room temp
- Hydrogen is made of small molecules
- So hydrogen chloride has weak intermollecular forces
- Intermollecular forces require little energy to overcome
How do you calculate bond energy?
1. Identify the bonds in reactants and products
2. Count the number of each type of bond
3. Look up bond energies in the table given
4. Multiply the number of each type of bond in the reactants by its bond energy then add them all together
5. Repeat the calculation from step 4 for products
6. Subtract the total of products from the total of reactants
State a risk of using chlorine
Its toxic
Whats an oxidation reaction?
a chemical process where a substance looses electrons
How do you calculate the mass of a product and the mass of a reactant?
1. Write out the balanced equation
2. Work out the relative formula masses of the limiting reactant and the product you want to find the mass of
3. Work out how many moles there are of the limiting reactant
4. Use the balanced equation to work out moles of product
5. Use the number of moles multiplied by the relative formula mass to find the mass
How do you work out the volume of gas
Volume of gass = mass of gas (g) divided by the relative formula mass multiplied by 24
How do you work out the number of moles?
Moles = mass in (g) of the element or compound divided by the relative formula mass
How do you work out concentration?
1. Calculate the number of moles of base used
2. Determine the mole ratio (e.g. 1:1 if there is equal moles on each side of the reaction)
3. Divide the number of moles of the substance by the volume of the solution to find concentration
Explain the benefits of using a pipette and a burette
Pipette measures a fixed volume accurately
Burette measures variable volume
Why are atoms neutral?
Because they have equal numbers of electrons and protons
What is the bonding of a metal with a non metal?
Ionic bonding
How would you draw the atomic structure of an element?
Nucleus in the middle
2 atoms in first shell
Then max of 8 in each outer shell
What is covalent bonding?
formed when a pair of electrons is shared between 2 atoms and it only occurs between non metal atoms
Describe the structure of a solid
Particles are held closely together in fixed positions by strong forces. The particles vibrate in their positions and as the temp increases they vibrate more
Describe the structure of a liquid
Weak forces between particles, they are randomly arranged and move freely past eachother but they tend to stick closely together. Liquids have a definate volume but not a definate shape
Describe the structure of a gas
Very weak forces of attraction. free to move, collide alot