Scientific Experiments. In Biology

Transcription

1 Scientific Experiments In Biology

2 In biology, some scientific experiments are done to study the factors affecting biological processes. For example, what are the factors that affect the rate (speed) at which osmosis occurs across a semipermeable membrane? First, you have to know what osmosis is!

3 Osmosis It is the movement of water molecules from an area of high water potential to an area of low water potential Check out the next slides to see this in practice

4 Osmosis Corn Syrup 1. Hypertonic High Water Potential 2. Low Water Potential De-shelled Egg

5 Osmosis Distilled Water 1. Hypotonic Low Water Potential 2. High Water Potential De-shelled Egg

6 What are some factors that affect the rate (speed) of osmosis 1. Concentration of solute in a solution 10% glucose 30 % glucose 60 % glucose. 2. Type of solute in a solution Glucose Sucrose Salt 3. Size of tissue used (Surface Area) 4. Temperature

7 Factors affecting the rate of osmosis

8 Concentration of solute in a solution In this experiment, different concentrations of sucrose are used to investigate the rate of osmosis. Controlled Variables Independent Variables Type of tissue: Size of tissue: Potato 2cm Potato strips Sucrose solutions with different concentrations Volume of solution: 10ml of solution Time: 30 minutes Dependent Variables Mass of potato strips

9 Setup Suitable equipment must be chosen Weighing plates Cork borer Knife Sieve Droppers Marker Test tubes Graduated cylinders Potato Stop Watch Beaker Forceps

10 Setup Suitable equipment must be chosen Sucrose Solutions with different concentrations

11 Setup A paper to record your data Mass before (g) Mass after (g) 0% % Sucrose % Sucrose % Sucrose % Sucrose 1 2

12 Step 1 Label the test tubes IMPORTANT!! - Label the test tubes according to the concentrations being used.

13 Step 2 measure 10mL of each solution 10 ml of each solution are measured

14 Step 2 measure 10mL of each solution 10 ml of each solution are measured Use a dropper to adjust the volume WARNING: USE DIFFERENT DROPPERS FOR DIFFERENT CONCENTRATIONS

15 Step 2 measure 10mL of each solution 10 ml of each solution are measured Use a dropper to adjust the volume WARNING: USE DIFFERENT DROPPERS FOR DIFFERENT CONCENTRATIONS Meniscus make sure the meniscus is at the 10mL mark.

16 Step 3 Filling the test tubes Pour the 10mL of the measured solution INTO THE LABELED TEST TUBE When you measure 10mL of 30% sucrose solution, pour them into the test tube labeled 30%.

17 Step 3 Filling the test tubes 0% 10% 30% 50% 70%

18 Step 4 Sampling Cork Borer

19 Step 4 Sampling Measure the diameter of the cork borer Use the cork borer to punch a hole in the potato all the way through WARNING!! DO NOT HOLD THE POTATO IN YOUR HAND WHILE DOING THIS STEP. YOU MAY INJUR YOURSELF!

20 Step 4 Sampling Push the tissue sample out of the cork borer using the needle

21 Step 4 Sampling After collecting cylindrical samples, remove the skin from each end

22 Step 5 measuring the length of samples 1. Measure 2cm for each sample 2. WARNING!! MEASURE IN cm NOT INCHES!

23 Step 5 measuring the length of samples After cutting up 2 cm samples, place them in the following manner For this experiment, you need 10 samples

24 Step 6 Weighing the samples First, Place the weighing plate over the balance

25 Step 6 Weighing the samples Locate the TARE button Push it to bring the scale down to ZERO

26 Step 6 Weighing the samples Use the forceps to collect a sample Place the sample in the dish

27 Step 6 Weighing the samples Return the potato sample back to its original place and record its mass Do the same for all the samples and record their masses WARNING!! Make sure the samples are returned back to the correct places

28 Step 7 immersing samples into solutions Use the forceps to take each sample and place it in the labeled test tube WARNING!! MAKE SURE THE SAMPLES ARE PLACED INTO THE CORRECT TEST TUBES

29 Step 7 immersing samples into solutions Use the forceps to take each sample and place it in the labeled test tube WARNING!! MAKE SURE THE SAMPLES ARE PLACED INTO THE CORRECT TEST TUBES

30 Step 7 immersing samples into solutions Do the same for the rest of the potatoes WARNING!! MAKE SURE THE SAMPLES ARE PLACED INTO THE CORRECT TEST TUBES

31 Step 8 Timing Once the last sample has been placed in the test tube, start the stop watch for 30 minutes

32 Step 9 Clean up your mess!

33 Step 10 - Collecting samples and weighing them 1. Take the first test tube Test tube 1 0% conc. WARNING!! DO NOT COLLECT MORE THAN ONE SAMPLE AT ONCE!

34 Step 10 - Collecting samples and weighing them 1. Take the first test tube 2. Pour the sample into the sieve

35 Step 10 - Collecting samples and weighing them 1. Take the first test tube 2. Pour the sample into the sieve 3. Use the forceps to collect the sample

36 Step 10 - Collecting samples and weighing them 1. Take the first test tube 2. Pour the sample into the sieve 3. Use the forceps to collect the sample 4. Use a towel paper to remove excess water

37 Step 10 - Collecting samples and weighing them 1. Take the first test tube 2. Pour the sample into the sieve 3. Use the forceps to collect the sample 4. Use a towel paper to remove excess water 5. Measure the mass of the sample Make sure the balance reads 0 before weighing your sample.

38 Step 10 - Collecting samples and weighing them 1. Take the first test tube 2. Pour the sample into the sieve 3. Use the forceps to collect the sample 4. Use a towel paper to remove excess water 5. Measure the mass of the sample Make sure the balance reads 0 before weighing your sample. 6. Return the sample back on the paper and record its mass after

39 Step 10 - Collecting samples and weighing them Repeat the same steps for each sample

40 Step 10 - Collecting samples and weighing them Repeat the same steps for each sample

41 Data Processing

42 DATA INPUT Use Microsoft Excel to input your collected data