Keys to writing a good discussion

• Remember you are writing the discussion assuming that the reader does not know the scientific theories, so when you make a statement you need to explain why it is a valid statement

•HAVE A PLAN: know what you want to cover in the discussion before you start writing it

•Don’t just say what happened. Tell me WHY!

• Don’t be overly brief, this is your chance to demonstrate your knowledge on the area of study and to explain the results you have collected

• Diagrams (particularly self created) are excellent ways of demonstrating your understanding

• Look for Trends / Patterns in your data (shows you have analytical skills)

•Don’t forget the error analysis section (discuss why there are some errors in the data you collected)

FORMAT OF THE DISCUSSION

1. Introduce the Key theory the experiment is based around, including an explanation of it, use diagrams, etc to help with clarity and depth

2. Draw attention to key pieces of data that demonstrate the scientific principal that your experiment is trying to prove (Fastest, Slowest, heaviest, lightest, highest, lowest, etc)

3. Identify any trends that can be found in the data (e.g. as the temp goes up, the reaction gets faster)

4. Discuss the data in the following way- Do the trends in the data match the outcome that scientific theory suggests should occur?- Refer back to the theory already stated, link your key data points to the theory -There will probably be a need to discuss parts of theory in more depth now to explain justify your results further

5.Draw attention to pieces of data the do not match the theory stated above. Discuss reasons / causes for possible errors in your data collection

KEY THEORY - PHOTOSYNTHESISPhotosynthesis is a chemical reaction occurring in plant cells which involves the

conversion of light energy from the sun into chemical energy in the form of Carbohydrates.

The Formula for photosynthesis is6CO2 + 6H20 C6H12O6 + 6H2O

The process is performed by all plant cells in an organelle called chloroplasts. The chloroplasts contain light absorbing pigments. There are several types of these pigments, the key pigments called Chlorophyll A & B.

Photosynthesis is essential for plant growth, as these carbohydrates are used to provide energy for the cell to perform mitosis (cell division)

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Key Pieces of DataThe plant covered with the clear Cellophane

demonstrated the most growth measuring an 11mm growth over the duration of the experiment, far more than the growth demonstrated by the plant under the Green Cellophane which showed only 2mm growth

It is also Notable that the Control plant (uncovered) also demonstrated high levels of growth showing a 10mm increase in height.

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TRENDS

• Trends: The general trend in the data collected shows that the plants continue to grow at a fairly constant rate, varying depending on the amount of light filtration they are exposed to.

It can be noted that this constant rate of growth is relatively consistent on all days of this experiment other than day 2 (refer to results table). All 5 test subjects displayed no growth on this day. It is possible that the cause of this change may have been due to lower light intensity on this day as a result of cloud cover. This decrease in light intensity would cause a decrease in the amount of light energy available for all plants to use for photosynthesis.

What

Why

Theory

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Discussing the data: Matching the Theory + Referrals to more theories

The results of the experiment indicated that plants grow better under un-filtered light than they do when exposed to a filter.

Of the filtered plants, the Red and Blue filtered plants showed similar growth of 7mm, with the Green filter showing only 2mm

These results are not unexpected as the filtering of light decreases light intensity, therefore is likely to decrease the amount of photosynthesis that will occur.

Of the Filtered plants, It was expected that the Green filter would show the least growth due to the tendency for the green coloured plant to reflect, not absorb the Green light getting through the filter.

Lead in statement, summary of the results

Brief statement about whether the results match the theories + Intro to the theories

Explaining the theoriesOn the previous slide, several more theories were brought up in order to justify the results, these include- The filtering of light- Reflection of light from coloured surfaces- Light intensities effect on photosynthesis- Chloroplast absorbance efficiency of varied colours of lights

It is now time to demonstrate your understanding of these laws/theories by explaining them and linking the explanations to the results

The use of Diagrams is also effective here.

*Note the an explanation is given, then highlighted in red, it is always made relevant by being linked back to this particular experiment

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ERRORS

The trend of data matches the scientific theory as predicted, however within the results were some anomalies.

It is notable that on Day 4 the plant under the green light actually recorded a loss of height.

This abnormality is most likely explained by an error in measurement during data collection as the method for measurement was not particularly sound.

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Filtering LightSunlight is known as white light, it is a combination of all visible light colours (refer to

diagram)

A filter acts as a light disperser, only allowing certain frequencies of light to pass through

When light is filtered, some energy is lost, therefore there is a decrease in light intensity. This explains why plants under filtered light do not show the same rate of growth as plants under unfiltered light.

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Reflection of Light from coloured surfaces

• Objects appeared coloured as a result of the frequency of light they reflect

A green object absorbs blue and red light, but reflects green light. This means that the majority of green light is reflected and does not enter the chloroplasts, therefore cannot be used for photosynthesis.

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Chloroplast Absorbance of Coloured Light

• Not all frequencies of light are as effective as one another for photosynthetic reactions (refer to graph below)

• Despite Green light being effectively usedby the chlorophyll, It has little effect in thiscase as the plant was green, thus the majorityof green light the plantwas exposed to was reflected before reachingthe chloroplasts.

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