Diffusion

What is diffusion?

The process where molecules move from an area of high concentration to an area of low concentration down a concentration gradient

What are control variables for concentration of HCL?

Temperature of agar blocks / acid

Surface area of agar blocks

Type of agar

Diffusion distance

Type of indicator

Volume of acid used

Ensuring that agar blocks are fully submerged 

Concentration of acid

What are factors that affect the rate of diffusion?

Concentration gradient

Temperature

Membranes

Surface area

Diffusion distance

Shape and size of molecules

How does concentration gradient affect the rate of diffusion?

The bigger the gradient the faster diffusion is

How does temperature affect the rate of diffusion?

As it increases the molecules gain energy so they move faster and diffusion rate rate increases

How does surface area affect the rate of diffusion?

The higher the surface area the faster the diffusion rate

How does membranes and barriers affect the rate of diffusion?

The more selective the membrane is the slower the diffusion will be only allowing certain molecules through

How does distance affect the rate of diffusion?

The shorter the distance the faster the diffusion because the molecules have to travel less

How does shape and size of the molecules affect the rate of diffusion?

The smaller or streamlined the molecules are the faster they diffuse

What are different equipment you can use to improve measuring accuracy for volumes and why?

A pipette - it has smaller scales and percentage error

Measuring cylinder

Why might an anomaly be present when doing an experiment on diffusion?

Diffusion may have happened slowly

Acid cooler than in trial 1

Diffusion took longer

Less agar covered by the acid

Used a lower concentration of acid so fewer particles to diffuse

What are more ways that you could extend a diffusion investigation?

Different acids

Different indicator

Different alkali in the agar

Different substrate for diffusion (gelatine instead of agar)

Different sizes / surface area of agar

Different volume of acid

Different concentration of acid

What can be some similarities and differences between someone else’s results and yours?

Different concentrations

Shape of cylinder

Type of alkali

pH of acid

Type/density of agar

Type of indicator

What are ways that you can ensure that results are accurate?

White tile - to see colours

Stopwatch - to give results to milliseconds

Read bottom of meniscus

Time taken in seconds - to give exact time for diffusion

use clean equipment for each test - no contaminations

Keep agar in container - to prevent early reactions