Biology Extended Experimental

Investigation

Rebecca Tkal12 B

Miss Johnstone

Table of Contents

1. Abstract........................................................................................................3

Aim................................................................................................................3

Hypothesis....................................................................................................3

Materials.......................................................................................................3

Method..........................................................................................................3

2. Introduction...................................................................................................4

3. Results.........................................................................................................5

4. Experimental Design....................................................................................5

Design of research........................................................................................5

Controls, dependent and independent variables..........................................5

Diagrams and photos....................................................................................6

Safety requirements......................................................................................8

5. Discussion....................................................................................................8

6. Conclusion....................................................................................................9

1. Abstract

Aim

The aim of this EEI is to examine the effects of microwaving on the concentration of Ascorbic Acid in a sample.

Hypothesis Based on research there should theoretically be a lower concentration of Ascorbic Acid (Vitamin C) in the solution, post the solution being microwaved.

Materials2 x vitamin C tablets400ml distilled water1x bottle of 1% starch solution1 x burette 1 x stand1 x clamp1 x funnel 1x 250ml bottle of iodine solutionAccess to 1x microwave25 x 50 or 100 ml beakers1 x large (250ml+) waste beaker.

Method

1. Prepare Ascorbic Acid Standard Solution 1. Dissolve 2 vitamin C tablets in 200ml of distilled

water.2. Add enough distilled water to make a 400ml

solution.

2. Standardise your solution.1. Add 25ml of Ascorbic Acid Standard Solution to a

beaker 2. 10 drops of 1% starch solution must be added to

the Ascorbic Acid solution. 3. Rinse the burette through with a small amount of

iodine solution and then fill it and record the initial volume.

4. Titrate the solution with iodine solution until the end point is reached. The end point is reached when the blue colour persists for longer than 20 seconds while swirling the solution.

5. Record the final volume of the iodine solution. 6. Repeat the titration at lease twice. The results

should agree to within 0.1ml

3. Microwave samples.

1. Divide the ascorbic acid solution into 16 x 25ml samples

2. Microwave 4 of the samples for 2 mins on high.3. Microwave 4 of the samples for 2 mins on low4. Microwave 4 of the samples for 2 mins on med5. The 4 other samples are titrated straight away.

4. Titrating your samples both microwaved and non microwaved. (Exactly the same as standardising your solution.)

1. Take non microwaved samples and titrate these first.

2. Microwaved samples are then titrated3. Titrate until the endpoint is reached. With iodine

this will be until the colour lasts longer than 20 seconds.

4. Record you results.

2. Introduction.

Observations and questions were raised of the worlds around us. These observations and questions included:

Allegations that microwaving destroys nutrients. Does microwaving negatively affect food? Focusing on vitamin levels Where plants choose to live depending on environmental factors. How plants adapt or change due to where they live. How plants grow due to environmental factors.

Research was conducted to refine the experiment. According to research all food undergoes chemical and biological changes when heated (source 2) Microwaves work by exciting the water molecules in the food or solution and heating the molecules from the inside out hence cooking the food from the inside out as opposed to a conventional oven which cooks from the outside in. (source 8) Although food cooked in a microwave may not present a radiation risk the presence of water soluble vitamins in vegetables means that the water molecules in these vegetables are excited and this results in a lower concentration of vitamins such as B12 and C in vegetables. (Sources 3 & 4 & 6) Therefore due to the research gathered the testing of a water soluble vitamin such as Vitamin C (ascorbic acid) is being carried out.

The aim of this EEI is to examine the effects of microwaving on the concentration of Ascorbic Acid in a sample.Based on research there should theoretically be a lower concentration of Ascorbic Acid (Vitamin C) in the solution, post the solution being microwaved

3. Results A table of results is recorded below

Trial 1 was the baseline trial. This trial was not microwaved. Trials 2-4 were micowaved for 2 minutes at varying intensities; high (100 power),

medium (50 power) and low (10 power) respectively.

4. Experimental Design

Design of research Titrations were used to determine the concentration of vitamin C as opposed to pH strips because of the ease of reading the volume of indicator. Ascorbic acid was the preferred vitamin used for testing for its solubility.

Controls, dependent and independent variables Independent Dependent

Changing of power in microwave no power, high (100power), medium (50 power), low (10 power).

Concentration of Ascorbic acid in solution due to microwaving.

SampleTrial 1 2 3 4

1 10.7ml 10.7ml 10.6ml 26.4ml2 18.7ml 18.8ml 18.8ml 18.4ml3 18.4ml 18.4ml 18.0ml 18.3ml4 18.0ml 17.9ml 18.1ml 17.8ml

Titration Results

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

SampleV

olu

me (m

l)

Result

Diagrams and photos

Ascorbic acid solution microwaved on medium power.

Rinsing burette

Solutions.

Safety requirementsGloves – staining and excessive iodine exposureLab coat – staining and excessive iodine exposure.

5. Discussion.When the non microwaved trial is compared to the microwaved trials there is an obvious change in the concentration of vitamin C in the solution. Within the microwaved samples there is a much smaller difference however the difference is still present. Between microwaved and the closest non microwaved sample there is an 8ml difference in the indicator volume for a reaction, a rather large difference. Amid the microwaved samples there is a much smaller difference. An average difference of .6ml between trials 2 and 3, and an average difference of .3ml between trials 3 and 4.

Anomalies of data excluded averages of trials are as followsTrial 1 – 10.6ml 1 anomaly excluded 26.4 possible higher concentration of ascorbic acid, small amount not dissolved.Trial 2 – 18.6mlTrial 3 – 18.2ml Trial 4 – 17.9ml

Future investigations that would prove useful would be the ability to test the concentration of ascorbic acid when it is heated by other methods such as boiling on a hot plate to determine whether the

6. ConclusionIt can be concluded from the results of the Extended Experimental Investigation that there was a lower concentration of Ascorbic acid after the ascorbic acid samples had been microwaved, thus supporting the stated hypothesis. Despite one anomaly the results were consistent with the hypothesis, both between trials that were microwaved and those that were not. The difference between the trials that were microwaved and those that were not gave the biggest difference between results. Between the trials that were microwaved the results were much closer nevertheless the gradual drop in the amount of indicator required to obtain a reaction was present.