investigating the effect of concentration on rate of diffusion

propose

look at the effect of changing concentration on the rate of diffusion in agar jelly

equipment

• cork borer

• dropping pipettes 3x

• ruler

• petri dish of agar jelly stained with phenolphthalein

• hcl - at different mol dm^-3

• stopwatch

health and safety considerations - phenolphthalein cubes

irritant

precautions- goggles, avoid touching with out goves

health and safety considerations - sodium hydroxide

irritant

precautions - goggles, spillage cleaned immediately, lab coat, wash hands

health and safety considerations - hcl

irritant

precautions - goggles, cleaned immediately, lab coat, wash hands if gotten liquid on skin

health and safety considerations - sodium hydroxide

irritant

precautions - goggles, clean spillage, wash hands if made contact, lab coat

health and safety considerations - glassware

could break and cause cuts

precautions - do practical in a tidy and even surface, any breakage cleaned immediately with a brush and a pan shuffle

iv - i change

concentration of hcl

dv - measure

rate of diffusion

• difference between a high-concentration area and a low-concentration area. A steeper, or larger, difference results in a faster, higher rate of diffusion

cv - keep the same

• agar concentration

• volume of hcl

• temperature

• time measured

relationship between con. of acid and the average

• As concentration increases the rate of diffusion increases

• very steep increase has a high level of direct proportionality.

when investigating the effect of concentration of the acid on average rate of diffusion its important to control the temperature - why?

• Temperature can also affect the rate of diffusion

• the higher the temperature the more kinetic energy the particles have

• and so the faster they diffuse

whats the biggest factor responsible for inaccuracy in the experiment - who can it be overcome

• Ensuring all wells diffuse for the same amount of time

• as it is very difficult to add the acid to each well at the same time and measure all three at the same time

• this can be overcome by using three separate people to be in charge of each well

using the concepts of repeatability and reproducibility, how to test the reliability in data

Repeatability

• repeat the experiment while using the same equipment

Reproducibility

• other students should carry out the experiment and compare results

other than using a larger range of concentrations, how to extend investigation further ?

• Use a different type of acid e.g. sulfuric acid

• Change the substrate diffusion occurs in, eg. gelatine instead of agar

• Change the surface area of the well use a different-sized cork borer

• Investigate different temperatures use a water bath to heat the acid