B4 05 OCR-H-gas exchange

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© Oxford University Press 2011

Learning OutcomesDescribe how molecules get into and out of leavesExplain the processes of diffusion

Gas exchange- diffusion

Keywords- diffusion, osmosis,

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What are the processes of living things?Write these on a whiteboard

Whiteboards-List the inputs and outputs needed by living things

diffusion is the way molecules get into and out of cells

How do these molecules move through the body tissues?

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So....what is diffusion?

Here is as example of diffusion in a gas

What is happening to the air freshenerSuggest an answer on a whiteboard

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Here is an example of diffusion in liquids

What happens to the tea colour?

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The tea molecules move from where they are highly concentrated into regions where they are less concentrated.

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After a few minutes the tea molecules spread evenly throughout the cup.

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Activity AB4.5.1 Diffusion with an investigation of diffusion in a gel.

How can we calculate the speed of diffusion?

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This swimmer’s cells need oxygen and glucose for respiration. They must get rid of carbon dioxide. These molecules move in and out of cells by diffusion.

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So diffusion is...The movement of molecules from where there are more or in high concentration to where there are fewer or in lower concentration.It is needed to allow molecules to move in and out of cells

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Looking at stomata

In this activity you used a microscope to look at the stomata on the under surface of a selection of different types of leaves

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Cross section of a leaf.

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suggest reasons for different speeds of diffusion in gels, liquids and gases. How is this related to particle theory and movement of molecules.

Suggest reasons for greater number of stomata on the lower surface of a leaf

how accurate are the experiments in determining the true value of diffusion rates and stomatal densities.

suggest why the measurements might not be true values

B4 05 OCR-H-gas exchange

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