Download - chapter 10 testing for nutrients lab

CHAPTER 10 BLM 10–5

SCIENCE INQUIRY Data Collection Sheet:Testing for Nutrients

Name: & Date:

Use this chart to organize your observations. (30 marks- ½ mark for each box)

Use these symbols:X- No color change

√-color change

Benedicts Solution

Iodine Biuret Solution

Brown paper

Food Samples Tests for Glucose

Tests for Starch

Tests for Protein

Tests for Fat


SCIENCE INQUIRY Testing Foods for Nutrients

Name: & Date:

Purpose Determine which nutrients are present in various food samples.

Apparatus

You need these at your station for all of the tests:

10 test tubes

test tube rack

3 medicine droppers (one for

each solution)

hot plate

tongs

Materials 10 food samples

Obtain these only when you

need them!!!

Biuret solution

iodine solution

Benedict’s solution

10 pieces of brown paper cut in

o 10 x 10 cm squares

Procedure

1. Make a full-page observation chart like the one shown here. You need to leave enough space to record 10 foods.

2. Use the chart to record colour changes during each test. A colour change indicates that you have identified the presence of a specific nutrient in a food sample.

3. Obtain 10 food samples. Place a sample of each food in a different test tube. Label each test tube with the name of the food that it contains. Use the same test tube for the same food sample in each test.

4. For each food sample, predict the nutrients it contains. Write your predictions on an observation chart titled “Predictions” like the one shown here.

PREDICTIONS- (30 marks- ½ mark for each box)

You need to finish this table before you start any of the tests. Please show this to me when you are done!

Test 1: Biuret SolutionNote: This is the test for protein. Biuret solution will turn from blue to violet (light purple) if protein is present.

1. Add 4 drops of Biuret solution to each sample.

2. Observe the colour after about 30 seconds.

Food Sample Prediction of what it

contains.Protein, Starch, Glucose(sugar),

Fat

Test 1:Biuret

Solution — Test

for Protein

Test 2:Iodine

Solution — Test

for Starch

Test 3:Benedict’sSolution —

Testfor Glucose

Test 4:Brown

Paper — Testfor Fat

EXAMPLE“Pop rocks”

Glucose, and fat

No color change

No color change

Dark blue to yellow or dark red

Darker and transparent

3. Record your observations on your chart. Mark an “X” if there is no colour change. If there is a change, record it by using a √.

4. Clean the test tubes.***If this is your last test clean up your station completely. You need to wash you test tubes out with soap and water. Before you go back to class to work on the questions you need to show me your station is clean***











Test 2: Iodine SolutionNote: This is the test for starch. Iodine will turn from an orange/red color to blue-black if starch is present.

1. Place a sample of each food in a different test tube.

2. Add 4 drops of iodine solution to each sample.

3. Observe the color after about 30 seconds.

4. Record your observations. Mark an “X” if there is no color change. If there is a change, record it by using a √.


Test 2: Iodine SolutionNote: This is the test for starch. Iodine will turn from an orange/red colour to blue-black if starch is present.


7. Add 4 drops of iodine solution to each sample.


9. Record your observations. Mark an “X” if there is no colour change. If there is a change, record it by using a √.

10.Clean the test tubes.***If this is your last test clean up your station completely. You need to wash you test tubes out with soap and water. Before you go back to class to work on the questions you need to show me your station is clean***

Test 2: Iodine SolutionNote: This is the test for starch. Iodine will turn from an orange/red colour to blue-black if starch is present.

11.Place a sample of each food in a different test tube.

12.Add 4 drops of iodine solution to each sample.

13.Observe the colour after about 30 seconds.

14.Record your observations. Mark an “X” if there is no colour change. If there is a change, record it by using a √.

15.Clean the test tubes.***If this is your last test clean up your station completely. You need to wash you test tubes out with soap and water. Before you go back to class to work on the questions you need to show me your station is clean***

Test 3: Benedict’s SolutionNote: This is the test for glucose. Benedict’s solution will turn from blue to a colour ranging from yellow to red if glucose is present.


2. Add 10 drops of Benedict’s solution to each sample.

3. Heat a beaker of water to 80°C on a hot plate.

4. Use tongs to suspend test tube 1 in the hot water bath for 2 minutes. Maintain the water temperature so the proper reaction will occur.

5. At the end of 2 minutes, remove the test tube and place it in a test tube rack.


7. Repeat steps 4 to 6 for each test tube.

8. Clean the test tubes***If this is your last test clean up your station completely. You need to wash you test tubes out with soap and water. Before you go back to class to work on the questions you need to show me your station is clean***

Test 3: Benedict’s SolutionNote: This is the test for glucose. Benedict’s solution will turn from blue to a colour ranging from yellow to red if glucose is present.


10. Add 10 drops of Benedict’s solution to each sample.

11. Heat a beaker of water to 80°C on a hot plate.

12. Use tongs to suspend test tube 1 in the hot water bath for 2 minutes. Maintain the water temperature so the proper reaction will occur.

13. At the end of 2 minutes, remove the test tube and place it in a test tube rack.


15. Repeat steps 4 to 6 for each test tube.


Test 4: Brown PaperNote: This is the test for fat. A grease spot will remain on brown paper if fat is present in the food.

1. Obtain 10 pieces of brown paper. Place a small sample of each food on separate pieces of brown paper. You may need to rub the food onto the paper. Be sure to label each piece of paper with the name of the food you are testing.

2. Let the samples dry for a few minutes.

3. Hold each piece of paper up to the light and look for transparent stains.

4. Record your observations. Mark an “X” if there is no change. If there is a change, record it by using a √.


Test 4: Brown PaperNote: This is the test for fat. A grease spot will remain on brown paper if fat is present in the food.

6. Obtain 10 pieces of brown paper. Place a small sample of each food on separate pieces of brown paper. You may need to rub the food onto the paper. Be sure to label each piece of paper with the name of the food you are testing.

7. Let the samples dry for a few minutes.

8. Hold each piece of paper up to the light and look for transparent stains.

9. Record your observations. Mark an “X” if there is no change. If there is a change, record it by using a √.



SCIENCE INQUIRY Testing Foods for Nutrients

Answer these questions in full sentences to get full marksAnalyze

1. Which food(s) contained a lot of glucose?______________________________________________________________________________________________________________________________________________________________

2. Which food(s) contained a lot of starch?______________________________________________________________________________________________________________________________________________________________

3. Which food(s) contained a lot of protein?______________________________________________________________________________________________________________________________________________________________

4. Which food(s) contained a lot of fat?______________________________________________________________________________________________________________________________________________________________

Conclude and Apply

5. Why do you think eggs and cheese are called “meat alternatives”?_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

6. Why do you think it was more difficult to identify nutrients present in some foods than in other foods?

_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Teacher Notes:

Safety Precautions

Handle all chemicals with care. Use caution when handling Biuret solution. It can cause irritation to the

skin and eyes, and may discolour clothing.

Use caution when handling iodine solution. Iodine can cause irritation to the skin and eyes, and may discolour skin and clothing. The vapours can be toxic if inhaled in large amounts. Clean up any skills immediately.

Use caution when handling Benedict’s solution. It can cause irritation to the skin and eyes, and may discolour clothing.

Note: This activity involves four tests. Each test requires some different materials and some different procedures. Be sure to read the instructions carefully.

Purpose• Students determine which testing agent to use to check for the

presence of glucose, starch, protein, and fat.

Science Background• Scientists use a variety of procedures to investigate the nutrients that foods contain. The purpose of this lab is for students to use some of the tests that scientists employ to identify fat, glucose, protein, and starch in foods.

Hints and Helps• Clear gelatin works very well and is easier to handle than egg whites.

• To help students visualize the amounts of nutrients contained in popular foods, set up a display. Measure a mass of glucose, starch, protein, or fat that is equivalent to the amount contained in a few popular food items (e.g., fries, doughnuts, potato chips, pizza, hamburger, apple). Students will gain an appreciation of the amounts of nutrients in some foods they may eat.

You might want to consider using prepared baby food for this activity. Although it is a bit expensive, baby food is pre-blended, which will save you time getting the materials ready for this activity.

•Clean-up will take a while. Make sure to leave enough time in the class to clean all test tubes used during this activity. In addition, the Benedict’s test requires students to heat the test tube in a hot water

bath. Some food items may cook inside the test tube, which makes it a bit more difficult to clean the test tube.

This lab includes 4 tests involving different procedures and materials for each.

Demo the brown paper by rubbing the food sample onto the paper and then drying it with a hairdryer. If the paper starts to look transparent, just like a grease mark of a MacDonald’s bag then you know the food has fat present.

Analyze Answers1. Fat — Test 4: Brown paperGlucose — Test 3: Benedict’s solutionProtein — Test 1: Biuret solutionStarch — Test 2: Iodine solution

2. More than one nutrient may be present in a food being tested.Note: If students followed the given lab procedures carefully, only one test tube should change colour during each test. Poor cleaning between tests might account for students reporting more than one test tube changing colour during a test.

Conclude and Apply Answers3. Glucose and starch.4. Answers may vary. Look for a reasonable answer such as testing unknown

food samples for nutrient content.