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How plants grow

Starter activity:

3 mins

Brainstorm - Where do plants get their food?

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Food in plants

maketheirown

photosynthesis

air

water

carbondioxide

lightenergy

nutrientsinsoil

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What types of food groups do you know?

Plants make food

write your answers here:

Protein

Starch

Fat

Minerals

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Carbohydrates - Starch

What do you know about starch?

Starch

carbohydrateturnsiodinepurple/darkblue

Storageofenergy

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How to test for starch in a leaf

Heat a beaker of water Take a leaf and place it in the hot water for 1

minute to soften it Place the leaf in hot ethanol until the leaf loses

it's colour Rinse the leaf in hot water to soften it Place the leaf on a white tile Test the leaf with iodine solution

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X

XX

XXXX

XX

XXX

Ethanol

Leaf

X

XX

XXXX

XX

XXX

HEAT

Testing a leaf for Starch

1

2

WARNING:

ETHANOL IS FLAMMABLE, DO NOT USE THE

BUNSEN WITH ETHANOL NEAR IT!

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Iodine Solution

Tile

Leaf

Iodine

Before

Iodine

After

Brown/ orange

purple/ dark blue

/ black

Test for Starch

*A positive test is when the iodine changes colour as a result of the presence of starch

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An example of a leaf test

After iodine solution is added to the leaf, the following may be observed:

Where are the positive results?

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Plenary:

What was the purpose of putting the leaf in:

a) boiling waterb) ethanol?

Homework:

Write a brief summary of your experiment today. What did you find out?

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Air and plants

Objective:

To know how oxygen and carbon dioxide affect plant growth

Read the following text and discuss the answers in groups. Be ready for class discussion

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The following experiment can be set up to show what happens when a leaf only has certain elements available

What do you think the results of a starch test will be for each leaf?Give reasons for your answers

Leaf A will produce a positive/ negative because...........Leaf B will produce a positive/ negative because...........Leaf C will produce a positive/ negative because...........

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So, the word equation for photosynthesis is:

carbon dioxide + water starch sunlight energychlorophyll

Summary:

Leaves produce starch when they are exposed to light, water and carbon dioxide.

Or is there more?

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Plants also give out a gas when the photosynthesise

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Investigating gas production by plants

You are going to investigate how light affects the rate of gas production in pond weed.

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Sc1 Skills

What do we know about scientific method?

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Prediction Hypothesis

Fair test Apparatus

Method Safety

Results Conclusion

Evaluation

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Prediction: Should relate two factors and state what happens to one if the other is changed

Hypothesis: The science facts you know related to the topic

Fair test: How you make sure you only change one factor

Apparatus: What basic hardware you used

Method: Bullet points of what you did

Safety: Basic lab rules

Results: What you found out in a clearly presented way

Conclusion: What you results show, relating to any patterns

Evaluation: How you could do your investigation better

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Factors (also called variables)

Independent variables

Dependent variables

What do you understand by the following terms?

Thisisusuallywhatwechoosetotest

Thisiswhatchangesasaresultofuschangingtheindependentvariable

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Examples:Pendulum

Independent variables

Dependent variables

lengthofstring

timetakenforswing

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acid

water

sodium

thiosulphate

Rates of reaction

Dependent variables

Independent variables

1.concentrationofacid

2.temperatureofchemicals

timetakentoreact

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Prediction - linking dependent and independent variables

If .................... changes, then ................... will happen.

If independent variable changes, dependent variable will result

Think about the examples we have looked at. Now write a prediction for the pondweed.

Independent variable = light intensity

Dependent variable = gas production (bubbles of gas)

Examples:

If the length of the string increases, then the time taken for the swing will increase

If the concentration of the acid increases , then the time taken for reaction will decrease

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If the light intensity increases , then the time taken for gas to be produced will decrease

Check your prediction against mine:

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Hypothesis: This is your chance to shine!

What topics do you need to cover?How much detail?

Write a paragraph of 3 - 4 sentences that explains what you know about:

What food plants makeWhat things plants need to make their own foodHow we can test this food is present

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Example hypothesis:

Plants store their food as starch. In order to do this they need sunlight energy, water and carbon dioxide. The leaves absorb carbon dioxide and water and store the starch. We can test for the presence of starch by using iodine solution which will turn dark blue/ purple if it is present.

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Fair tests:

water

sodium

thiosulphate

temperature

concentration

surface area

stirring

volumes of

reagents

acid

What should we do to make a fair test?

How do we make this a fair test for the pondweed?

Change only one factor at a time

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Method: How much detail should you include?

Write 2 methods

Method 1 - short, 5 steps

Method 2 - detailed, 10 steps

How much do you really need to say?What is necessary in a method?

We all know how to make a sandwich. So, if I said to you that I wanted a method on how to make a cheese sandwich, how much detail would you use?

Take 2 slices of bread Butter the bread Add cheese Put the slices together Serve

Walk to the kitchen Wash hands Take bread Open bag Take out 2 slices Place on clean work surface Use 2g of butter for the bread Add 5 g cheese Put slices together Serve

Do I need all of these steps?Which ones are useful? Why?

Detailed methods are good but only if the right details are added

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Apparatus:

2-D neat diagrams, of a page.Use sharp pencil and a ruler

How much information should you include?

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Safety:

What are basic safety rules in the lab?

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Results:

What do want to show?What should a good results section contain? How many results do I need?Do I need repeats and average numbers?

How much information should I include?

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http://www.saddleworth.oldham.sch.uk/science/simulations/waterweed.htm

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dependent variable

independent variable

Light intensity

bubble count

x

y

0 100

35Hints for a good graph:

If you can't remember the axis labels. 'X' is a-cross, so put it on the axis that goes across

Start at 0 for each axis Use regular intervals for your scales Choose a scale that is easy to read Look where the independent variable goes Try to use the whole page to draw your graph

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Light intensity (units)

Bubble count

0 1 2 3 4 5 6 7 8 9 100

5

10

15

20

25

30

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Rate of photosynthesis

estimating missing values

What do you notice about my 'line of best fit'? Is it straigh