Milk/Glue Lab Objectives: The objectives of this intermediate lab are to practice filtration and observe a precipitation reaction and a neutralization reaction. Materials Needed: Each group will need the following materials: 1. 3. 5. 7. 9. Skim milk, 125 mL 2. Beaker, 250 mL Acetic acid (Vinegar), 25 mL 4. Heat source (Hot plates) Sodium bicarbonate (Baking soda), 1g 6. Funnel and filter paper Stirring rod 8. Water, 30 mL Graduated cylinder, 125 mL 10. Goggles Strategy: 1. Place 125 mL of skim milk in a 250 mL beaker. 2. Add 25 mL of Acetic acid (vinegar), which is an acidic solution. 3. Gently heat milk and stir constantly until small lumps begin to form. 4. Remove beaker from heat and continue to stir until no more lumps form. 5. Allow lumps to settle. 6. Filter the solid (curds) from the liquid (whey) using a funnel. 7. Gently press the filter paper around the curds to squeeze out the excess liquid through the filter paper. Dump liquid down the drain and run the water. 8. Return the solid to the beaker 9. Add 30 mL of water to the solid and stir 10. Add 1/2 tsp. of Sodium bicarbonate (baking soda) to neutralize vinegar, bubbles should appear. Add a little more baking soda until no more bubbles appear. 11. The substance in the beaker is glue. Test the adhesive properties by placing the glue in between two pieces of paper. 12. CLEAN UP YOUR LAB STATION! Performance Assessment: Questions to answer in your lab report: 1. What is the purpose of the Acetic acid (vinegar) in making glue? What is the purpose of the heat? 2. How is the casein (protein) separated from the milk? 3. What is the purpose of the Sodium bicarbonate (baking soda)? Background Information Milk Composition: 87.7% Water 4.9% Lactose Up to 3.4% Fat 3.3% Protein 0.7% Minerals The difference between Skim Milk, 50% Fat Milk, and Whole Milk is the fat content! Vocabulary Words: Curd- The part of the milk that coagulates. Coagulate- The cause transformation of a liquid into a soft, semisolid, or solid mass. Whey-The liquid remaining after the milk has been curdled. Casein Protein-A phosphoprotein found in cow milk. As a food source, casein supplies amino acids, carbohydrates, calcium, and phosphorus.