A safe method is to do the following:

1. Estimate the number of scale bars which fit into the image, and estimate the length. 
   In this case about 6 or 7 scale bars so 60 - 70 µm length.
2. Measure the length of the diagram in milimetres (not cm - because it's  easier to divide a larger number and avoid decimals).
3. Measure the length of the scale bar in milimetres.
4. Divide the length of the diagram by the length of the scale bar and multiply by the size written on the scale bar.
   e.g.  140mm length /  20mm scale bar x 10µm  = 70µm

To calculate magnification you only need the scale bar.

1. Measure the length of the scale bar in mm
2. Convert this to the same units as written on the scale bar
3. Divide the actual diagram size by the measurement written on the scale bar.

For example

1. length of scale bar is 20mm
2. this is 20 000 µm
3. so the magnification is 20 000 / 10 = X2000

 How to do an estimate of the cytoplasm concentration.

1. When the solution is the same as the cytoplasm concentration there will be no change in mass.
2. Draw a best ft line on the graph and estimate where it crosses the 0.0 mass change.
3. This is about 0.07 mol.

Other factors which could affect the rate of osmosis could be:

• temperature
• the time allowed for diffusion
• shape of the potatoe cyllinders
• type of potato
• skin on the potato
• checking that all the salt has dissolved in the solution

These values show the uncertainty or the measurement.

+/- 0.05g means that a reading of 0.10g could be as little as 0.05g or as much as 0.15g.
(The axis scale really should also have 2d.p. so that it matches the uncertainty)
It is certain to be in between these values but we cannot know more precicely, because of the measuring equipment used.

The same logic can be applied to the concentration values. 0.10 mol could be 0.08 - 0.12 mol

Both of these 'uncertainties' are quite small, much smaller than the differences between concentrations shown on the graph, so we can infer that the data presented is quite reliable.

There are two forces acting on the pigments during the chromatography:

• The pigments adhere to the paper
• The pigments are carried by the solvent

Because each pigment is made from a different molecule the forces are different.

Molecules which adhere to the paper very strongly don't move very far, those which only attach lightly to the paper move further.

Smaller molecules tend to get carried further by the solvent, as do those which dissolve more easily in the solvent.

The distance a pigment travels depends on the paper, the solvent and these forces.

Distance of solvent front from the base line = 33 mm

Distance of the centre of pigment A from the base line = 29 mm

Rf value = 29 / 33  = 0.88

The closest pigment to the Rf value of 0.88 is Carotene with an Rf value of 0.91.

In order to see any pattern in the results there needs to be a range of buffer solutions covering pH5 to pH9 at least.  A wider range would be better.  This experiment would have 5 different pH values tested, pH5,6,7,8, and 9.

Each pH would need several repeats to check the reliability of the results.  Three repeats would usually be sufficient.

The enzymes from the liver will contact the hydrogen peroxide on it's surface only. So although mass is important so will be shape as this will change the surface area if it is different.

The IB guidelines state that animals should not be subjected to conditions outside the range of conditions they experience in nature.  It is very likely that 80°C, and 60°C will cause harm, or kill the maggots.

It would be better to test the maggots at 5 temperatures between 10°C and 40°C.

There are lots of practical difficulties:

• Cutting the bottles is a bit dangerous and you must hold the bottle in such a way that you cannot stab you hand with the scissors as you make the first cut into the bottle.
• The edges of the bottle must be the same size, and neatly cut to ensure a good seal.
• If you use a glue gun there is a need to be careful not to burn yourself.
• Putting the soil in without dropping too much into the water is tricky unless you have a long spoon / spatula.
• Care must be taken to ensure that there is enough photosynthesis to provide oxygen for the spider. 
  Pond weed is a good idea as it is likely to survive well, given enough light.

This is really a question about experiment design. 

There would need to be five identical mesocosms each containing the same organisms.

Each mesocosm would be given a different lighting regime
(e.g. 4 ours / day, 8 hours /day, 12 hours /day, 16 hours and 20 hours.)

A measure of the number of animals, and plants after a period of several weeks would be recorded.

Measurements could be taken each week for a couple of months, or even longer.

For more reliable results more mesocosms would be needed so there could be repeats.

The movement of the water in the capillary tube would been measured using the apparatus.

The time taken for the movement.

The rate would be calculated by dividing the movement by the time taken.

Better still the volume of water evaporated divided by the time taken.

If there was a bubble of water under the filter paper then the bubble would expand in size and the water in the capillary tube would not move.

As the jogging speed increases the ventilation rate increases at a constant rate.

There is a possitive correlation between joggins speed and ventilation rate.

The depth of each breath would also increase (especially at slower jogging speeds)

There is a limit to the volume of a breath, the tidal volume of the lungs.