1. The document provides instructions for students to make bioplastic from milk through a chemical reaction with vinegar. It involves mixing milk and vinegar, which will separate into two phases - casein and serum. The casein phase is filtered and dried to produce the bioplastic. 2. The procedure involves mixing heated milk with vinegar and monitoring the pH at various steps. The mixture will separate into curds (casein) and whey (serum) due to acidification. 3. Advantages of bioplastics over conventional plastics are discussed such as biodegradability and renewable sourcing. Disadvantages may include limited applications and higher costs compared to petroleum-based plastics.

1. BIOPLASTICS
TECHNOLOGY 3º ESO
NAME : _______________________________
MEMBERS OF THE TEAM: ___________________________________________________________________
OBJECTIVES
 Make bioplastic from milk
 Understand the chemical reaction
 Measurement of pH
 Discuss about advantages and disadvantages of using bioplastics
QUESTION: WHAT HAPPENS WHEN MILK AND VINEGAR ARE MIXED?
HYPOTHESIS:
MATERIALS:
 250 cc whole milk
 _________
 ___________
 Vinegar
 ___________
PROCEDURE AND RESULTS (please, fill in the table while doing the experiment)
1. Pour 250 cc of milk in the beaker
2. Measure the pH of the milk using the strips
3. Heat the milk (avoid boiling! 60ºC-65ºC aprox) teachers will do it
4. If you want to colour your plastic, you can add a few drops of food colouring before this step.
5. Pour 40-50 ml of vinegar in the graduated cylinder.
6. Measure the pH of the vinegar using a new pH strip.
7. Pour the vinegar over the milk and stir the mixture during 1 minute, aprox. As you stir, you should
notice that clumps will start to form. If no clumps form, the milk was probably not hot enough for
the reaction to occur.
8. Measure the pH of the mixture.
9. When you observe 2 parts, separate them by filtration (using the strainer or the lab paper)
10. Remove the water from the solid part, as much as possible
11. Pour the plastic onto a smooth surface covered with foil or film. If you want to mould the plastic
into a specific shape, you will need to do it during this step.
12. Dry out during 1-2 days
Volume of the milk
Milk pH
Milk temperature after heating
Vinegar pH
Mixture pH
Time needed to dry
Mass of bioplastic
DATE ________
SCORE
 2 pH measurement strips
 ___________________
 Stirring rod
 Cloth strainer or filter lab paper
 ___________
 Colouring food (optional)

2. QUESTIONS
1. Make sure that you have filled the hypothesis box. Make sure that you have filled in the gaps
that appear in material. Fill in the table above.
2. Why two phases appear?
3. One phase is called serum (suero) and the other casein (caseína). From which part bioplastic
is obtained?
4. Make a list of the words that appear underlined in procedure and translate them or explain
the meaning.
5. The final product is a type of plastic. BIOPLASTIC. Make a list of the main differences
between this plastic and the industrial types we have studied before, for example PET or
number 1.
6. Make a drawing that represents the experiment. Label each scene (make an infographic)
7. What have you learned by doing this activity?