Osmosis: THE INVESTIGATION!!

IGCSE Combined Science

Before you begin, have you.......

1. put your Science hat on ?!

2.got a Lab Report Format in front of you?

3.got a Combined Science checklist next to you?

Make sure you do this for EVERY science report!

TITLE: a brief, concise yet descriptive title

• I will normally give this to you (because I am nice )

• This lesson we will be investigating..

The Effect of Different Sucrose Concentrations on Osmosis

in Potato Cells

BACKGROUND: Include any preliminary observations or background information

about the subject• What do YOU remember

about osmosis in plant cells?

• Can you include a diagram?

• Have you used all your relevant key words?

Generate IdeasGenerate Ideas

Change

Measure/observe

Hazards and risks

Which variable might affect…

What will be our

evidence?

HYPOTHESIS: What do you think will happen and why?

• As the concentration of the solution ________, the mass of the potato will______ because.......

• In distilled water the mass of the potato will _______, because........

• Can you link this to your background?

MATERIALS: a list of what you need to carry out the experiment

• Can you list all the equipment required for this experiment?

• You WILL be given;0.1M, 0.3M, 0.5M sucrose solutions

• Distilled water

VARIABLES: both IV and DV need to be clearly identified• Independant Variable:

This is the thing YOU are changing in your experiment

• Dependant variable:This is the thing YOU are measuring in your experiment

How will you make this experiment a fair test?

• An investigation or experiment where only the independent variable has been allowed to affect the dependent variable.

• This means only changing one variable and keeping everything else the same.

• This way you know that ONLY the variable YOU changed could cause a change in the results

• What do you need to keep the same in your experiment?

c

Let’s make a questionLet’s make a question

The variable I will change is..

I variable will measure/observe is

m

c

These variables I will keep the same

ccc

c c

METHOD: How will you carry out this experiment?

• Use passive sentences

• Use third person pronouns

Instead of.... Write....

We tested the specimen... The specimen was tested...

I measured the mass... The mass was measured...

Instead of.... Write....

We found that... It was found that....

We conclude that… It was concluded that...

Could someone on the other side of the world follow your instructions and reproduce your experiment EXACTLY???

Try reading your method to a partner. Can they follow your instructions?

Example!!!!

1. I got some paper

2. Then I folded and fixed the paper to make a sign and then I wrote my name on it

3. Stand up so you everyone can see you and wear your hat

1. Write your name in capital letters on a strip of paper. Ensure the letters use as much of the paper as possible

2. Ask a partner to fold the paper strip around your head so it sits comfortably .

3. Ask your partner to tape the strip behind your head to make a loop.

4. Stand upon your desk whilst wearing your paper loop around your head

Things you need to think about!

• What volume of solution will you add to each test tube?

• How long will each piece of potato be? How will you measure this?

• How long will you leave it for?

Method1. Cut a length of potato using a cork borer2. Cut 4 2cm pieces of potato using a scalpel and ruler3. Use a measuring cylinder to measure 10ml of distilled

water into a test tube. Repeat for 0.1M, 0.3M and 0.5M sucrose solutions.

4. Record the initial mass of the first piece of potato and then drop it into the distilled water.

5. Repeat step 4 for the other 3 solutions.6. Leave the experiment to run for 40 min7. Remove each piece of potato and record the final mass8. Calculate the change in mass of the potato for each

solution and display the results as a bar graph

RESULTS: • How you will you record your

raw data?

• How will you process your data in order to make sense of it?

• Have you thought about-units?-a title?

Table of ResultsTable of Results

changec m

GRAPH: what kind of graph are you going to draw?

• It depends on whether your data is....

• Continuous Data that is measured on a scale. Examples could be size, weight and diameter of holes.Always a LINE GRAPH

• DiscontinuousData that can be put into categories such as gender (males and female) and colour.always a BAR CHART

Rules for graphs• Use a pencil and ruler.• Choose a sensible scale for each axis.• Axes do not have to start at zero

• Go up to a little more than the biggest number• Label each axis, including units (in brackets)

• Plot the points carefully with a pencil.• Join the points for a line graph

• For a bar graph, label each bar underneath it.• Give the graph a title – in pen and underlined.

Sketch what YOUR graph will look like....

Concentration of solution (M)

Change in mass (g)

CONCLUSION: accept/reject your hypothesis using data from your graph

• What happened and why?

• Is this what I thought would happen?

• What evidence have I got that supports my findings?

• Has this proved or disproved a some of my scientific understanding?

Evaluating the Fair TestEvaluating the Fair Test

• F – Fair. Did we keep the investigation fair?

• A – Accurate. Did we measure/observe accurately?

• R – Reliable. How much trust can you have in your results?

Would you change anything about your investigation if you were to do it again?