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A-Level Biology PAG 9.3
Benedict’s reagent
A chemical solution used to test for reducing sugars by changing color in their presence.
pH paper
A tool used to measure the acidity or alkalinity of a solution, ensuring it is neutralized to pH 7.
Qualitative test
A test that determines the presence or absence of a substance, such as reducing sugars, without measuring quantity.
Semi-quantitative results
Results that provide an estimate of the concentration of a substance, often using color changes.
Calorimeter
An instrument used to measure the amount of light transmitted through a solution, aiding in quantitative analysis.
Why does eye protection need to be worn
Due to the presence of boiling water and acid
What is step one of both method 1 and 2
Label the boiling tubes and and 4cm³ of the corresponding samples using a fresh syringe each time
What is step 2 of method 1
Add 2cm³ of Benedict’s
What should you do after each stage
Record observations
How long should each sample spend in the water bath for method 1
4 minutes total
After how long should you remove a sample from the water bath and record observations
2 minutes
What is step 2 for method 2
Add 2cm³ of hydrochloric acid to each sample
What is the role of the sodium hydrogen carbonate
To neutralise the acid
What should stop once the acid is neutralised
Effervescence (Bubbling)
How can you test to make sure the acid has been neutralised
Add a small drop onto pH paper
What colour should a neutral solution be
Green
