PAG 9.3 - OCR

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