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What's in Our Food?

This worksheet will explain the chemical tests that can be used to identify different things in our foods.

Key stage:  KS 3

Curriculum topic:  Biology: Structure and Function of Living Organisms

Curriculum subtopic:  Nutrition and Digestion

Difficulty level:  

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QUESTION 1 of 10

Food provides us with the energy to grow and move and helps keep all the parts of our body working properly.   

 

 

Marathon runners often have a meal high in carbohydrates the night before a race to provide them with the slow releasing energy they need to run.

 

It is important for us to know then exactly what is in our foods so we can ensure we are getting the balanced diet that our bodies need. Below are a few tests that can be used to show if fats, proteins, starch or sugars are present in the foods we eat.

 

The Chemical Tests for Carbohydrates

There are two types of carbohydrate. One is starch and the other is sugars.

The test for starch is using a chemical called iodine. When added to something containing starch, iodine will turn from a red/brown colour to a blue/black colour.

The test for sugars is using a chemical called benedict’s solution. When added to something containing sugars, benedict’s solution will turn from blue to orange.  

 

The Chemical Test for Proteins

The test for protein is using a chemical called Biuret solution. When added to something containing protein, Biuret solution will turn from a blue colour to a pink/purple colour.  

 

The Chemical Test for Fats 

The test for fats is not quite as simple as the tests for carbohydrates and protein. It requires 2 steps:

Firstly, add the food to be tested to a small amount of ethanol and let it dissolve (the solution may need to be heated in order for it to dissolve fully. DO NOT USE A BUNSEN BURNER OR A NAKED FLAME, ethanol is highly flammable therefore a water bath should be used.) 

If the solution remains colourless, there are no fats present. If a layer of cloudy white emulsion forms at the top, then there is fat in this type of food.  

Complete the following sentence by writing the missing word in the box below:

 

There are two types of carbohydrates, starch and ____________ .

What chemical(s) would you use to test for carbohydrates? 

Iodine

Benedict's

Biuret

Ethanol

The presence of sugars will cause Benedict's solution will change from blue to what colour?

The night before a race, marathon runners normally have a meal high in which food group to provide them with the slow releasing energy that they need to run?  

protein

fat

carbohydrates

vitamins

Match up the correct food type with the chemical used to test for it.   

Column A

Column B

starch
Biuret
protein
Benedict's
sugars
Iodine

Which of the following solutions is used to test for proteins?

Iodine

Benedict's

Biuret

Ethanol

Ethanol is used in the 2 step process of testing for fats. The food substance being tested must be added to a small amount of ethanol and the ethanol must then be heated to allow the food to dissolve.  

 

Why must a Bunsen burner not be used to heat the ethanol?

The Bunsen burner will not heat the ethanol to a high enough temperature.

Ethanol is highly flammable.

Ethanol is a gas at room temperature.

Which of the following chemical solutions will change from red/brown to blue/black in the presence of starch.  

Iodine

Benedict's

Biuret

Ethanol

In the chemical test for fats, which of the following will indicate that presence of fat in the food being tested? 

a colour change from blue to orange

a colour change from blue to pink/purple

a colour change from red/brown to blue/black

the formation of a milk like emulsion

A student wants to find out what food types are present in a sample of food. They test the sample with different chemicals and get the following results.  

 

Chemical Observation
Iodine no change
Benedict's solution Benedict's solution changed from blue to orange
Biuret solution no change
Ethanol A white (milk-like) emulsion formed 

 

From the above results, what food types are present in the food sample?

fats

proteins

starch

sugars

  • Question 1

Complete the following sentence by writing the missing word in the box below:

 

There are two types of carbohydrates, starch and ____________ .

CORRECT ANSWER
sugars
sugar
  • Question 2

What chemical(s) would you use to test for carbohydrates? 

CORRECT ANSWER
Iodine
Benedict's
EDDIE SAYS
Iodine is used to test for starch. It will turn from red/brown to blue/black.
Benedict's solution is used to test for sugars. It will turn from blue to orange.
  • Question 3

The presence of sugars will cause Benedict's solution will change from blue to what colour?

CORRECT ANSWER
orange
EDDIE SAYS
Benedict's solution will change from blue to orange in the presence of sugars.
  • Question 4

The night before a race, marathon runners normally have a meal high in which food group to provide them with the slow releasing energy that they need to run?  

CORRECT ANSWER
carbohydrates
EDDIE SAYS
Carbohydrates will provide long distance runners with slow releasing energy throughout the race.
  • Question 5

Match up the correct food type with the chemical used to test for it.   

CORRECT ANSWER

Column A

Column B

starch
Iodine
protein
Biuret
sugars
Benedict's
  • Question 6

Which of the following solutions is used to test for proteins?

CORRECT ANSWER
Biuret
EDDIE SAYS
Biuret solution will change from blue to pink/purple in the presence of proteins.
  • Question 7

Ethanol is used in the 2 step process of testing for fats. The food substance being tested must be added to a small amount of ethanol and the ethanol must then be heated to allow the food to dissolve.  

 

Why must a Bunsen burner not be used to heat the ethanol?

CORRECT ANSWER
Ethanol is highly flammable.
EDDIE SAYS
Ethanol is highly flammable so must never be used near a naked flame.
  • Question 8

Which of the following chemical solutions will change from red/brown to blue/black in the presence of starch.  

CORRECT ANSWER
Iodine
  • Question 9

In the chemical test for fats, which of the following will indicate that presence of fat in the food being tested? 

CORRECT ANSWER
the formation of a milk like emulsion
  • Question 10

A student wants to find out what food types are present in a sample of food. They test the sample with different chemicals and get the following results.  

 

Chemical Observation
Iodine no change
Benedict's solution Benedict's solution changed from blue to orange
Biuret solution no change
Ethanol A white (milk-like) emulsion formed 

 

From the above results, what food types are present in the food sample?

CORRECT ANSWER
fats
sugars
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