Diffusion and Osmosis Mini-Lab

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Cecilia Phelps
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1 Diffusion and Osmosis Mini-Lab In this lab, you will be conducting two pairs of mini experiments to look at the two processes in which cells allow materials to enter and exit their cellular membrane. A) Diffusion Experiment: Materials: Food colouring Water Ice cubes 60 ml Beakers x 3 Electronic tea kettle Thermometer Timer/Stopwatch Predictions: Before starting your experiment, read the Procedure below and predict what you think will happen to the food colouring droplet in each of the three water-filled beaker (1. Ice cold water; 2. Room temperature water; 3. Boiling hot water). Ask yourself, will there be any differences in the time it takes for the water to turn a uniform colour in each of the three beakers? Write your prediction below: 1

2 Procedure: 1) Boil two cups of water in an electronic tea kettle. 2) Label your three beakers as: Cold, Room Temperature and Hot. 3) Fill the first beaker with 40 ml of very cold tap water (place an ice cube or two into the water to make it even extra cold) 4) Fill the second beaker with 40 ml of room temperature water. 5) Fill the third beaker with 40 ml of boiling water from the kettle. 6) If possible, use a thermometer to determine the temperature of the water in each beaker. Record your temperature results in the table below under Observations. 7) At the same time, place three drops of food colouring into each beaker and start your timer/stopwatch. Record how long it takes for the water in each beaker to be a uniform colour throughout. Observations: Complete the table below with the recorded information you obtain from carrying out the procedures of your experiment. Beaker #1 Ice Cold Water #2 Room Temperature Water #3 Boiling Hot Water Water Temperature ( C) Time it takes for the water to turn a uniform colour throughout. Concluding Questions: 1. What cellular process was this experiment portraying? Explain why. 2

3 2. Compare your prediction to the results you obtained. Was your prediction correct/incorrect? Explain the differences below. 3. What can you conclude about the effect of water temperature on the time it takes for the dye to become a uniform colour throughout the water? 3

4 B) Osmosis Experiment: Materials: Two plates medium plates with a raised edge 1 small russet potato (cut in two halves lengthwise) Water Salt Tablespoon Predictions: Before starting your experiment, read the Procedure below. One potato half is soaking in a pool of freshwater, while the other potato half is soaking in a pool of salt water. What do you think will happen? Write your prediction below. Procedure: 1) Look at your two potato halves and describe, with as much detail as possible, what the potato looks like (only the raw interior of the potato). For example, look at things like colour, firmness, smoothness, and moisture level. Record your observations in the table below. 2) Lay out your two plates and fill them both with the same amount of water 3) Measure out two tablespoons of salt and sprinkle it into the water in only one of the dishes. 4) Make sure you label which dish has the salt, and which dish doesn t 5) Place one potato half with the flat side down onto one dish, and the other half down on the other dish. 6) Wait about 2 3 hours for the potatoes to soak in the water then record your observations in the table below (make note of what the interior of each potato slice now looks like). 4

5 Observations: Complete the table below with the recorded information you obtain from carrying out the procedures of your experiment. Note: Only make observations of the raw interior side of the potato. Some things to look for include: colour, firmness, smoothness, and moisture level. Observations Before Observations after of Potato in ONLY Water. Observations after of Potato in Water and SALT. Concluding Questions: 1. What cellular process was this experiment portraying? Explain why. 2. Compare your prediction to the results you obtained. Was your prediction correct/incorrect? Explain the differences below. 5

6 3. What can you conclude about the effect of immersing a potato in just water? Explain, biologically, what is occurring. Draw a diagram below to help visualize your explanation. 4. What can you conclude about the effect of immersing a potato in water and salt? Explain, biologically, what is occurring. Draw a diagram below to help visualize your explanation. 6

Part 1: Food Coloring & Water

Part 1: Food Coloring & Water Name: Hour: Biology Unit 3-Cells Diffusion & Osmosis Lab Activities Cells use various processes of diffusion and osmosis in order to transport particles throughout a cell and across the cell membrane.