Materials

■ safety goggles

■ disposable gloves

■ labeling tape

■ 10 mL graduated cylinder

■ Benedict's solution

■ 9 dropping pipets

■ glucose solution

■ unknown solution

■ distilled water

■ 9 glass stirring rods

■ tongs or test-tube holder

■ albumin solution

■ sodium hydroxide solution

■ copper sulfate solution

■ vegetable oil

■ Sudan III solution

Background

1. Carbohydrates, proteins, and lipids are nutrients that make up all living things. Some foods, such as table sugar, contain only one of these nutrients. Most foods, however, contain mixtures of proteins, carbohydrates, and lipids. You can confirm this fact by reading the information in the Nutrition Facts box found on any food label.

2. In this investigation, you will use chemical substances, called indicators, to identify the presence of specific nutrients in an unknown solution. By comparing the color change an indicator produces in the unknown food sample with the change it produces in a sample of known composition, you can determine whether specific organic compounds are present in the unknown sample.

3. Benedict's solution is used to determine the presence of monosaccharides, such as glucose. A mixture of sodium hydroxide and copper sulfate determines the presence of some proteins. This procedure is called the biuret test. Sudan III is used to determine the presence of lipids.

Procedure

CAUTION Put on a lab apron, safety goggles, and gloves. In this lab, you will be working with chemicals that can harm your skin and eyes or stain your skin and clothing. If you get a chemical on your skin or clothing, wash it off at the sink while calling to your teacher. If you get a chemical in your eyes, immediately flush it out at the eyewash station while calling to your teacher. As you perform each test, record your data in your lab report, organized in a table such as the one on the next page.

Test 1: Monosaccharides

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