experiments to know

Question 1

practical: how much heat is released in the combustion of a fuel?

Answer 1

set-up: fuel under test tube filled with named mass of water. held by rod. thermometer inside test tube.
method:
- measure the mass of the spirit burner before heating. measure the temp of the water before heating.
- heat for a certain amount of time or until the temp reaches a certain point
- measure mass of burner and temp.
- calculate mass and temperature change.
- use temp change to work out Q, then mass change and Q to work out energy released.
mistakes:
- heat lost to surroundings when flame is burning and incomplete combustion
- replace lid on spirit burner at the end to avoid some fuel evaporating and making moles burnt seem bigger than it was
conclusions:
- usually lower than actual value, due to lots of mistakes

Question 2

how can a graph be generated to prove that small chips react faster than big chips?

Answer 2

set-up: conical flask with bung on top

Question 3

simple distillation

Answer 3

Flask contains solution we want to separate with a bung on top which has a thermometer running through it. Condenser is surrounding by a water jacket and is connected to the flask. End of condenser runs into beaker. Bunsen burner under flask.
Method:
- Heat up mixture (vapour), which rises to the top of the flask and is then forced into the condenser, where it condenses due to the cooler temperature. The liquid is collected in the beaker. Eventually, the solid will be left in the flask.

Question 4

fractional distillation

Answer 4

Used when the substances we are separating have similar boiling points. Mixtures of liquids.
Same set up as simple distillation, but the vapours pass through a fractionating column before going through the condenser. Its full of glass rods – high surface area. Tall – so cooler at the top than at the bottom. The glass rods cool the vapours with higher boiling points so only the correct liquid gets through.

Question 5

filtration

Question 6

how to calculate rf

Answer 6

rf value = distance dye has moved / distance solvent has moved

Question 7

what to do if chromatography hasn’t worked on one dye

Answer 7

repeat with a different solvent, e.g. alcohol