Thinking Allowed

blood orange by Derek Purdy on flickr

For this lab you are going to test a range of fruits (lemon, orange, mango, tomato) and determine their vitamin C content.  Here’s how:

Vitamin C is an antioxidant.  It changes DCPIP (a dye) from blue to colourless. 

1. Use a pipette to add some of the vitamin C solution, drop by drop to 2cm3 of DCPIP in a test tube.
2. Shake the tube gently after the addition of each drop.
3. Continue until the solution is decolourised.
4. Record the exact volume of vitamin C added.  Repeat and average results.
5. Calculate the mass of vitamin C required to decolourise 2cm3 of DCPIP, knowing that the vitamin C solution was made to contain 1mg of vitamin C in 1.0cm3 of water.
6. Using a similar technique, compare the vitamin C contents of several different fruits.
7. To determine the volume of the fruit, place it in a beaker and cover with water.
8. Mark the level of the meniscus on the outside of the beaker.
9. Remove the fruit, make the water up to the mark with water from a measuring cylinder.  The volume of water added is equivalent to the volume of the fruit.

This comes from Practical Advanced Biology by King, Reiss and Roberts.

When you write up your lab report, include the data collected and the processing of it, though I will not award this a separate grade (as I have told you how to do it).  State your conclusions and write a detailed evaluation.  I will grade this according to the IB rubric. Conclusion and evaluation rubric

Here are a some questions for consideration:

• Vitamin C is derived from a 6-carbon sugar.  Suggest why it is so abundant in fruits and what functions it may serve.
• A typical adult requires about 10mg of vitamin C per day, though governments recommend between 30 and 60 mg.  To what extent can these needs be met by a single piece of fruit?
• Can you find out what effect storing or cooking has on the vitamin C content of foods?

Due date for this is Tuesday 19th January If you would like me to take a look at your draft then get it to me by 7.30am Monday, the day before.

ReactionTimeStepTwo from www.csiro.au

This next lab looks at measuring reaction times.  There are several ways we could do this, but we are going to keep it simple and use the old, tried and tested method of catching a ruler.  Here’s what to do:-

1. Find a partner.
2. One person rests their elbow on a table with their hand extended over the edge.
3. The partner should hold a meter ruler between the subject’s thumb and forefinger, ensuring it is at the 0cm mark.
4. As soon as the ruler is released, the subject must try and catch it.  The distance the ruler falls can be used as a measure of reaction time.
5. You will need to repeat this a suitable number of times to ensure the reliability of your data.
6. Try investigating different variables, such as left-hand vs right-hand, using one eye or two eyes, sound or touch stimuli instead of sight.  THINK ABOUT CONTROL OF VARIABLES – it is very important here.
7. Record your data in a suitable way, process it and present it appropriately.  Draw relevant conclusions.  Evaluate your results and the procedure used.  Suggest realistic improvements.

This lab will assessed for data collection and processing, and for conclusion and evaluation.

 DUE DATE:  Tuesday 17th November

We will be doing a lab comparing the properties of ionic and covalent compounds, and trying to answer this question:

How are the properties of substances explained by theories of structure and bonding?

Read the instruction sheet for full details: LAB – How are the properties of substances explained by theories of bonding and structure

Here is a really useful presentation, thanks to Mr Hobbins. How your Heart beats

Please also continue to work on your heart rate labs.  See the rubric below.  Due on OCTOBER 1st.

Listed below are some of the finer points that are often the difference between a ‘c’ and a ’p’ grade in an aspect. You should be able to answer ‘yes’ to each of the questions.

DP Biology Lab Report Format

Please follow this format for each practical investigation – it will help us see that you have covered all of the aspects that are needed to be marked ‘Complete’.

1. Research question or aim:  Clear and to the point. State the dependent and independent variables and species name [e.g. Apis mellifera] in the research question

2. Hypothesis: Predictions with reasons based on scientific theory or published data. What do you think is going to happen with reasons based on scientific theory or published data. This is then stated as a prediction as what you think will happen in your experiment. IF (independent variable) THEN (dependent variable) BECAUSE..”

3. Variables: Independent, Dependent, Controlled (a list here is enough).

4. List apparatus and materials (with amounts/sizes/quantities).

5. Method to control variables: Keep at least 3 factors constant to reduce experimental error.  Give a reason for each one.

6. Method for collection of raw data: What are you changing? How? What are you measuring? How? What units? How many data points will you produce? State them clearly. What will you do with the data collected?

7. Large, clear diagram or photo of set-up, clearly labeled.

8. Collect and record raw data, giving units and uncertainties.  e.g. using a mm ruler, error is +/- 1mm

9. Present the raw data in a large, clear, self-designed table. Give an informative title.  i.e. – ‘table of results’ is not descriptive enough.

10. Process raw data: Choose an appropriate graph/ chart/ statistical test.  Perform it correctly, giving a worked example for all calculations used.

11. Present processed data: Make table or graph large, clear and well labeled.  Include units and an informative title.

12. Draw conclusions: What do your results tell you?  What does this mean? Explain using scientific theory.  Does it agree with your hypothesis?  Compare collected data with published (literature) data if possible. Reference it appropriately.

13. Evaluate procedures and results: Identify (min 3) weaknesses, limitations and errors in the results and the method.

14. Improve the investigation: Suggest realistic methods to improve on each of the weaknesses mentioned above.

15. References.

Use this checklist, thanks to Mr. Hobbins, to help you with your heart rate lab.

Listed below are some of the finer points that are often the difference between a ‘c’ and a ’p’ grade in an aspect. You should be able to answer ‘yes’ to each of the questions.

DP Biology Lab Report Format

Please follow this format for each practical investigation – it will help us see that you have covered all of the aspects that are needed to be marked ‘Complete’.

1. Research question or aim:  Clear and to the point. State the dependent and independent variables and species name [e.g. Apis mellifera] in the research question

2. Hypothesis: Predictions with reasons based on scientific theory or published data. What do you think is going to happen with reasons based on scientific theory or published data. This is then stated as a prediction as what you think will happen in your experiment. IF (independent variable) THEN (dependent variable) BECAUSE..”

3. Variables: Independent, Dependent, Controlled (a list here is enough).

4. List apparatus and materials (with amounts/sizes/quantities).

5. Method to control variables: Keep at least 3 factors constant to reduce experimental error.  Give a reason for each one.

6. Method for collection of raw data: What are you changing? How? What are you measuring? How? What units? How many data points will you produce? State them clearly. What will you do with the data collected?

7. Large, clear diagram or photo of set-up, clearly labeled.

8. Collect and record raw data, giving units and uncertainties.  e.g. using a mm ruler, error is +/- 1mm

9. Present the raw data in a large, clear, self-designed table. Give an informative title.  i.e. – ‘table of results’ is not descriptive enough.

10. Process raw data: Choose an appropriate graph/ chart/ statistical test.  Perform it correctly, giving a worked example for all calculations used.

11. Present processed data: Make table or graph large, clear and well labeled.  Include units and an informative title.

12. Draw conclusions: What do your results tell you?  What does this mean? Explain using scientific theory.  Does it agree with your hypothesis?  Compare collected data with published (literature) data if possible. Reference it appropriately.

13. Evaluate procedures and results: Identify (min 3) weaknesses, limitations and errors in the results and the method.

14. Improve the investigation: Suggest realistic methods to improve on each of the weaknesses mentioned above.

15. References.

Here is the instruction sheet for this lab, along with the rubric.  Lab – Demonstrating Absorption You will be assessed on conclusion and evaluation only for this lab.  You need to submit the following by Tues 15th Sept – either soft or hard copy.

A copy of the lab sheet.  Your hypothesis, including justification. Your data tables. Your conclusion and evaluation.

maximum heart rate 214 by Laurel Fan on flickr

In class this week and next we will be working on a lab dealing with factors affecting heart rate.  Your task is simple – to design, carry out and write up your findings on how a particular factor affects heart rate. 

Begin by listing all the factors you can think of that might influence how fast or slow your heart beats.  Decide on one independent variable to test, and write it in the form of a research question.  Next write a hypothesis, including justification.  Then plan an experiment to test your hypothesis, remembering to state clearly how you will control all the variables you mentioned earlier. 

Then comes the fun part – performing your plan.  You may need to ask, beg, bribe some of your classmates or family members to participate.  Once you have your data, process it and present it appropriately, explain your findings, and evaluate both your results and your method.  Suggest improvements for next time. 

Phew!  That should take a while…. This is a great opportunity for you to boost your IA scores and gain complete on the various aspects of lab grading.  Here is the  IA rubric.

For this first lab report on Murphy’s law, we are taking it nice and slow, and working together in class for much of the time.  In the future, you will be expected to write up the experiments more independently.  Here is the rubric, or something very similar,  that will be used to assess your work.  Integrated Science Rubric for assessing Lab Investigations.

You are in the process of writing up a lab report on demonstrating absorption and digestion.  Block B students have already had a lesson on this and are due to submit their final version to me, either electronically or on paper, by THURSDAY 27th AUGUST.  Block F students have until FRIDAY 28th AUGUST (We will spend next Tuesday on this so don’t panic!).  Please make sure you see me during tutorials if you need help.  Our next unit will be on the transport system (the heart, blood and blood vessels), so read your textbook if you want to get a head start on this.