p1 practicals

Question 1

investigate paper chromotography using inks/food colourings

Answer 1

1) draw a line near the bottom of a sheet of filter paper - this is known as the baseline using pencil as it’s insoluble
2) add spots of different inks to the line at regular intervals
3) loosely roll the sheet up and put it in a beaker of solvent
4) make sure the level of solvent is below the baseline so the inks dont dissolve in the solvent
5) place a lid on top of the container to stop the solvent evaporating
6) the solvent seeps up the paper, carrying the inks with it
7) each different dye in the inks will move up the paper at a different rate and form a spot in different places
8) when the solvent has nearly reached the top of the paper, take the paper out of the beaker and leave it to dry

Question 2

determine the formula of a metal oxide by combustion

Answer 2

1) Measure the mass of the crucible with the lid

2) Add a sample of magnesium into the crucible and measure the mass with the lid (calculate the mass of the metal by subtracting the mass of the empty crucible)

3) Strongly heat the crucible over a Bunsen burner for several minutes

4) Lift the lid frequently to allow sufficient air into the crucible for the magnesium to fully oxidise without letting magnesium oxide smoke escape

5) Continue heating until the mass of the crucible remains constant (maximum mass), indicating that the reaction is complete

6) Measure the mass of the crucible and its contents (calculate the mass of metal oxide by subtracting the mass of the empty crucible)

Question 3

investigate the solubility of a solid in water at a specific temperature

Answer 3

1. Pour 200 cm3
   of deionised water into a 250 cm3
   beaker.
2. Use a water bath to heat the beaker of water to the desired temperature. Keep the
   thermometer in the beaker to ensure the temperature stays constant throughout the
   experiment.
3. Add known masses of the solid bit by bit until it stops dissolving and remains as solid in the
   solution.
4. Record the mass of solid that was soluble.
5. Repeat steps 1-4 with the water at different temperatures.

Question 4

reduction of copper (II) oxide to form copper

Answer 4

1. Measure the mass of the empty reaction tube. Add the copper oxide to the reaction tube
   and remeasure the mass of the reaction tube. Calculate the mass of copper oxide added to
   the tube by subtracting the first mass from the second.
2. Clamp the reaction tube horizontally using the clamp and stand.
3. Connect the delivery tube to a supply of methane and secure the bung in the reaction tube.
4. Switch on the methane supply and wait a moment before lighting the methane at the hole
   where it escapes the reaction tube.
5. Use a bunsen burner to heat the copper oxide from the underside of the horizontal reaction
   tube.
6. Heat until the metal oxide completely changes colour. This means all the oxygen has been
   reduced. Turn off the supply of methane.
7. Measure the final mass of the reaction tube. Calculate the mass of copper formed.

Question 5

investigate the electrolysis of aqueous solutions

Answer 5

Sodium Chloride:
Method
1. Set up the apparatus as shown in figure 1. The two electrodes should be connected to the
power pack using crocodile clips and wire.
2. Half fill a beaker with the sodium chloride solution. Place the electrodes into the beaker,
making sure they do not touch.
3. Turn on the power pack to 3V and leave for 2 minutes.
4. Record any observations that occur whilst the experiment is being carried out.

Question 6

determine the aproximate percentage by volume of oxygen in air using a metal or non-metal

Answer 6

1. Place wet iron filings inside the end of a burette. Use vaseline to make the filings stick.
2. Using a clamp, stand the burette vertically over a trough of water.
3. Record the starting height of the water in the burette.
4. Leave for a few weeks then record the final height of the water in the burette.
5. Calculate the change in height of the water in the burette. This is the volume of oxygen that
   was originally in the burette.
6. To calculate the percentage by volume of oxygen in air, divide the change in the burette
   reading by the original volume of air in the burette and multiply by 100.

Question 7

the reactions of metals with hydrochloric acid

Answer 7

1. Set up the apparatus as shown in figure 1. The measuring cylinder must be filled with water
   before being placed upside down in the water trough. The delivery tube should run from the
   conical flask into the measuring cylinder.
2. Place 100 cm3
   of hydrochloric acid in the conical flask.
3. Record the start volume of water in the upturned measuring cylinder.
4. Record the mass of one magnesium ribbon then add it to the acid. Immediately attach the
   bung and delivery tube and start the timer. Record any observations.
5. After 30 seconds record the new water level in the measuring cylinder. Calculate the
   volume of gas that has been produced. Use this value to calculate the rate of reaction.
6. Repeat steps 2-5 using zinc foil and then iron foil, using a similar mass of metal in each
   experiment. Make sure the measuring cylinder is refilled before adding the metal to the
   acid