Lab Book

Question 1

Calibration of a microscope:
What are the three steps to calibrate a microscope (before sums)?

Answer 1

Line up the zero of the eyepiece graticule and the zero of the stage micrometer

Make sure the scales are parallel

Look at the scales and see where they are in line again

Question 2

Sum : add in later!

Question 3

Sum

Question 4

Sum

Question 5

Food tests:
Specification reference?

Answer 5

Spec ref: 1.1
Chemical elements are joined together to form biological compounds

Question 6

Food tests:
What are the five tests you need to know and understand how to use?

Answer 6

Reducing sugars
Non-reducing sugars
Proteins
Starch
Fats and oils

Question 7

Food tests:
Reducing sugars

What’s the method?
What test solution in used?

Answer 7

1. Mix 2cm^3 of the test solution (glucose) with an equal volume of Benedict’s reagent
2. Heat the mixture in a water bath between 70 and 90 degrees C for 5 minutes
   (Tip: remember to put Ben in the bath)
3. Record your observations

Question 8

Food tests:
Reducing sugars

What will you observe?

Answer 8

Starting colour = blue

No glucose present = no colour changes

Glucose present = any change away from blue, the difference in colour indicates the amount of glucose present

Blue —> green —> yellow —> brown —> orange —> brick red

Question 9

Food tests:
Non-reducing sugars

What’s the method?
What test solution is used?

Answer 9

1. Mix 2cm^3 of the test solution (sucrose) with an equal volume of Benedict’s reagent.
2. Heat the mixture in a water bath to between 70 °C and 90°C.
3. Observe and record colour change.
4. Put another 2cm^3 of the test solution into a boiling tube, add 2 drops of hydrochloric acid and heat in a water bath to 70 °C and 90 °C for 2 minutes.
5. Add 2 drops of sodium hydroxide/ small spatula of sodium bicarbonate.
6. Add 2 cm^3 Benedict’s reagent.
7. Heat the mixture in a water bath to between 70°C and 90°C for 5 minutes.
8. Record your observations.

Question 10

Food tests:
Non-reducing sugars

Why do you add acid?
What will you observe?
What is used to see if it is acidic or neutralised?

Answer 10

You add acid to break sucrose down to glucose and fructose

Observation: blue —> brick red

Acidic or neutralised? Litmus paper

Question 11

Food tests:
Proteins

What’s the method?
What test solution in used?

Answer 11

Method:

1. Mix 2cm^3 of the test solution (albumin/ egg white) with 2cm^3 of Biuret reagent in a boiling tube
2. Cover the top of the boiling tube and invert it once
3. Record your observations

Question 12

Food tests:
Proteins

What will you observe?

Answer 12

Biuret reagent =
light blue —> purple

Question 13

Food tests:
Starch

What’s the method?
What test solution in used?

Answer 13

1. Mix 2cm^3 of the test solution (starch) with 2 drops of iodine in potassium-iodine solution
2. Record the colour change

Question 14

Food tests:
Starch

What is the colour change?

Answer 14

Yellow/brown —> blue/black

Question 15

Food tests:
Fats and Oils

What’s the method?
What test solution in used?

Answer 15

1. Mix the fat or oil with 5 cm^3 of absolute alcohol (ethanol) in a boiling tube.
2. Shake the tube.
3. Pour the mixture into another boiling tube half full of cold water.
4. Record your observations.

Question 16

Food tests:
Fats and oils

What’s another name for the test?
What will you observe?
Why?

Answer 16

Emulsion test is another name

The fat separated and sits on top to create a milky suspension of the lipid. This is because alcohol breaks down the fat