misszara
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The older the berry, the sweeter the juice” is a quote from a film.
Design an experiment to test if this statement is true for blackberries, assuming that the juice contains GLUCOSE (not sucrose)

1. Introduction. Use scientific terminology to explain why the comments/observations in the first paragraph could be correct.

2. Experimental design – write an experimental plan as a list of simple and easy-to-follow instructions which includes how valid results could be collected. Could include a diagram to support.
Discussion and Evaluation – Discuss how confident you could be with any conclusions you might be able to draw from your experiment and the reasons why you are/are not confident. Suggest ways in which any aspect of your experiment could be improved to gain more accurate data.
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gordi..1
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hey..did you find help..if no let me know
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misszara
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(Original post by gordi..1)
hey..did you find help..if no let me know
No I haven’t yet
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izzy888
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Which exam board is this?! never seen a question like this before... All I can say is the test for glucose is Benedict's solution, which turns from blue to either green, yellow or brick-red depending on the strength. Sorry!
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misszara
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(Original post by izzy888)
Which exam board is this?! never seen a question like this before... All I can say is the test for glucose is Benedict's solution, which turns from blue to either green, yellow or brick-red depending on the strength. Sorry!
Hey, it’s not on the exam board, although I am doing AQA. Its like a use-your-knowledge question but I am so stuck! Thank you tho
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gordi..1
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(Original post by misszara)
Hey, it’s not on the exam board, although I am doing AQA. Its like a use-your-knowledge question but I am so stuck! Thank you tho
i texted several times u never replied...come we talk its all about agreement
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macpatgh-Sheldon
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misszara

Hi there!

I think Izzy has hit the nail on the head.

Basically experiment can be as follows:-
1. Introduction. Use scientific terminology to explain why the comments/observations in the first paragraph could be correct.

When a fruit is not so ripe, it is more likely to contain sour chemicals like citric acid (named after citrus fruit), and ascorbic acid [vitamin C], and we know that acids are sour. As a fruit ripens, pectinases break down pectins so it becomes softer, but also more glucose is stored within it. Glucose is also called simple sugar - it is a hexose [has six carbon atoms] but can also be called a reducing sugar, and the fruit is sweeter when ripe cos of this extra glucose [sugars are sweet].

2. Experimental design – write an experimental plan as a list of simple and easy-to-follow instructions which includes how valid results could be collected. Could include a diagram to support.
Discussion and Evaluation – Discuss how confident you could be with any conclusions you might be able to draw from your experiment and the reasons why you are/are not confident. Suggest ways in which any aspect of your experiment could be improved to gain more accurate data.

DESIGN:
---a) Take two lots of berries - one lot picked from a mature climber, and one from a climber grown a month later [young].
Make sure the temp remains the same for both.
---b) Weigh 100 g from each sample to use for experiment.
---c) Crush the berries, and filter off the juice using filter paper and a funnel.
---d) Take 30 cm3 of the juice from each sample.
---e) For each, [describe how you would test for glucose [or any reducing sugar] with Benedict's solution - use your book/notes].
---f) Using a simple colorimeter, check the density of red-brown colour produced.
---g) The greater the colour density, the higher the amount of glucose.


---h) Repeat the experiment once again from a) to g).

Discussion:
Confident: a) We used equal weights of berries for each sample then equal volumes of juice, so results may be reliable.
b) We kept temp constant for storing juice, so any decomposition of chemicals that might introduce an error are less likely.
c) We repeated the experiment to make results more reliable.

Not confident: a) We used only one colour density [single wavelength of light] to estimate colour density and hence glucose level. Yellow colour occurs with less glucose, which we did not allow for. We could use a different titration method e.g. the type of test used to measure glucose in the blood of patients with diabetes.
b) There may be other reducing sugars present e.g. fructose, which might give an overestimate of glucose levels. We could think of a more specific test for glucose alone [see a) above).
c) Other way round: we are testing for sweetness, which might be caused by non-reducing sugars in the fruit e.g. sucrose. We could heat the juice with sodium hydroxide before Benedict's test to break down sucrose into glucose + fructose to give separate values for different types of sugars.

Best of luck and be safe!
Sheldon.
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