Science 8th grade
UNIT 6: Stated of matter 6.3 Investigating diffusion
Science 8th grade
UNIT 6: Stated of matter 6.3 Investigating diffusion
Using diffusion
To make tea in a teapot, you pour boiling water onto the tea leaves. Particles from the tea leaves diffuse into the hot water. You can make the tea stronger and darker by leaving the tea leaves in the pot for a longer time. You can make the tea stronger by using more tea leaves. You can stir the tca leaves to make your tea stronger more quickly.
To make a drink using fruit syrup, you add water to the concentrated syrup. When you add water from a tap, the water particles and fruit syrup particles get mixed up. If you add the water slowly and very gently you have to wait for the syrup to diffuse through the water.
Activity 6.3A (What are the factors that speed up or slow down diffusion?)
SE: Different factors affect the rate at which particles diffuse.
1) Discuss in your group the factors that might be involved. Some things to think about might be the size of the particles; the mass of the particles; the state of matter, temperature. Make a list of these factors.
2) In your group, discuss and make a prediction about how each of these factors affects diffusion. For example: I think that if we increase the temperature diffusion will be quicker.
3) In your group, discuss and explain your prediction for each of the factors.
For example: I think diffusion will be quicker if we increase the temperature because the particles will have more energy and can move more quickly.
Planning an investigation needs a lot of thought.
Activity 6.3B (Investigating how temperature affects diffusion)
SE: You will use water and ink or food dye. You will very carefully place a drop of ink into a test tube of water and time how long it takes until the water is completely coloured. You will do this with water at different temperatures.
1) Make a prediction about what will happen in your investigation. Explain the reasons for your prediction.
2) Make a list of the equipment you will need.
3) How many different temperatures will you use?
4) What are the highest and lowest temperatures you will use? This is the range of temperatures.
5) What interval will you use in temperatures between the highest and lowest?
The interval is the step between one temperature and the next. Will you go up in ${1^ \circ }C$, ${5^ \circ }C$ or ${10^ \circ }C$ steps?
6) Which variables will you keep the same?
7) Explain how you will make your investigation a fair test.
8) Explain how you will ensure your results are reliable.
Reliable means that you would get the same results if you repeat your experiment.
9) Draw a results table.
When you have had your work checked by your teacher you may carry out the investigation.
Questions
${A_1}$: Plot a graph of your results. Put the temperature along the horizontal axis and the time along the vertical axis.
${A_2}$: What do your results show?
${A_3}$: Do you have enough results to form a conclusion?
${A_4}$: Was your prediction correct?
${A_5}$: Explain your results.