What could’ve gone wrong? These plants are the same species so why are they so different?

How does gas exchange happen in plants? Diffusion How does gas exchange happen in plants? Lesson Learning Outcomes: Define the term diffusion Carry out experiments into the rate of diffusion Describe how gases enter and leave a leaf Increasing Difficulty 2

Dictionary definition Diffusion: the movement of particles from a region of higher concentration to an area of lower concentration

Diffusion Experiments Copy the following table: Medium Distance/m Time/s Speed m/s Gas Liquid Solid Make a prediction, demo gas and solid, studnets carry out tea practical and work out liquid

Liquids Your task is to carry out diffusion in liquid Pour water into the beaker (about 200ml) Measure the distance from the bottom of the beaker to the top of the water line in the beaker using a ruler and record it in your table Put in the tea bag and push it to the bottom with the stirring rod Start the stop clock and time how long it takes for the water at the top to become tea coloured. Record this in your table then calculate the speed

Draw a storyboard Think about the tea, how did the tea get from the bottom to the top Try to describe the stages using the word diffusion Now exchange books and try to draw a molecular diagram to explain

Diffusion The particles are separate when first put together. They slowly start to mix due to their random motion. The particles are now nearly fully diffused. The particles are fully diffused. 7

Rate of diffusion Steep concentration gradient Diffusion increases if there is a steeper gradient… Steep concentration gradient Shallow concentration gradient 8

Plants... A leaf

Plants Many small pores, called stomata, mostly on the lower epidermis A stoma

Gas Exchange... In the light: Carbon dioxide diffuses into the leaf through the stomatal pore The carbon dioxide diffuses through the air space Then it diffuses into the cells

Gas Exchange... In the light: Oxygen diffuses out of the cells into the air space Then it diffuses out through the stomata to the surrounding air REMEMBER: diffusion relies on a concentration gradient!

Gas Exchange... In the dark: Oxygen diffuses into the leaf taking the same path as carbon dioxide in the light

Summarise Draw two pictures to show how carbon dioxide and oxygen are exchanged in leaves in the light and in the dark

To set up for next time... We are going to set up an experiment for next lesson. In pairs you have been given a sucrose concentration Use a core borer to cut a tube of potato Use the knife to cut the potato to 4cm Weigh the potato and record it in the back of your book Collect a test tube and write your initials on the test tube and the concentration you were given Put 30cm3 of your sucrose solution concentration into the tube Pop it on the side until next week