STAGE 2 BIOLOGY PHOTOSYNTHESIS TASK SHEET BASIC METHOD

Transcription

1 STAGE 2 BIOLOGY PHOTOSYNTHESIS TASK SHEET BASIC METHOD Materials: Fresh green leaves (e.g. Ivy) 50mL plastic syringe 50mL measuring cylinder 2x100mL glass beaker distilled water 6% sodium bicarbonate solution (source of CO 2 ) Cork borer or a hole punch Overhead projector stopwatch Method: 1. Cut 10 leaf discs using the cork borer or hole punch. Transfer these discs into a 100mL beaker containing distilled water. 2. Leave the beaker in a refrigerator overnight this should assist in extracting most air from the leaf discs. 3. Transfer the discs, along with 20mL of distilled water, into a 50mL plastic syringe. Expel the air. 4. Either place a rubber stopper or a finger over the hole. Vigorously pull the plunger in and out. You should notice gas forming on the inside of the syringe, expel the air. You have successfully de-gassed the leaf discs when the discs sink to the bottom of the syringe. 5. Extract the discs from the water by pouring the syringe contents into a sieve. Immediately transfer them into a 100mL beaker with 50mL of 6& sodium bicarbonate solution. 6. Turn the overhead projector on immediately and start the stopwatch. Record the time, in seconds, for each disc to rise. Take note of any discs that do not fit the pattern of discs rising. 7. Calculate the average of the time taken for the discs to rise. 8. To calculate the rate of photosynthesis calculate the reciprocal of the average time and then covert it to scientific notation. E.g. Average time taken for the discs to rise = 250 sec Rate of photosynthesis = sec -1 = 4.0 x10-3 sec -1

2 DESIGN Introduction: Aim: Hypothesis: Remember: a hypothesis is a prediction of the results of the investigation. Independent variable: Dependent variable: Constant variables: Identify how you plan on keeping the variable constant e.g. identify volumes used if that is something that will be kept constant. Safety: Relevant MSDSs checked and important things noted: Hazards identified and minimised:

3 Abstract: Aim/Hypothesis: Method (a two sentence summary): Summary of results: An abstract is a brief summary of the whole practical report. The headings only show what things you need to include. DO NOT include these headings in the abstract. Conclusion: Results: Create a suitable table here that includes your independent and dependent variables.

4 Discussion: (space for notes) Data: What kind of association is demonstrated in the graph? OR If there wasn t enough data for a trend, why not? Only use the Discussion heading. The other subheadings here are only a guide to assist you in writing your discussion. How does this relate to the hypothesis/aim? Are there any outliers? Why might they have occurred? (Ignore if there were none) General improvements: What could be improved about the method? There might be some general improvements that are not linked in with errors. You can include them. How did it affect the results/efficiency/safety/etc? How could it be improved?

5 Random Errors: What was the random error? How did it affect the results both generally and specifically? Explain things concisely. Don t use fancy words when simple words suffice. Remember: random error affects precision. How could you change the method to reduce the effect of this error, and hence improve the investigations? (You can suggest more than one thing) What was the random error? How did it affect the results both generally and specifically? How could you change the method to reduce the effect of this error, and hence improve the investigations? (You can suggest more than one thing)

6 What was the random error? How did it affect the results both generally and specifically? How could you change the method to reduce the effect of this error, and hence improve the investigations? (You can suggest more than one thing)

7 Systematic Errors: What was the systematic error? Remember: systematic error affects accuracy. How did it affect the results both generally and specifically? Explain how redoing the experiment with different equipment would help to identify a systematic error. Conclusion: Answers the aim/hypothesis.

8 SA:V RATIO - Practical Assessment Student s initials: Category Skills Checklist Comments Set up of work area Has all apparatus required Apparatus logically set out at work area No unnecessary hazards present Uses work area methodically Measurement of volumes Uses appropriate measuring apparatus Carefully measures volumes Meniscus touches graduation line for required volumes Uses the correct volumes as per the method Other Precise leaf discs are cut. All leaf discs sink to the bottom after gas extraction Time measured precisely Beaker labelled appropriately Area cleanliness Keeps work area logically set out for the entire investigation Does not put wet implements on bench space Careful when navigating around the work area Cleans up any spillages or breakages(as necessary) N/A Clean up Disposes of solutions appropriately Leaf discs disposed of appropriately Puts all used apparatus in the appropriate containers Is aware of hazards during cleanup