Lab - Law of Conservation of Mass (Day 2)

Learning Intentions

  • To understand the Law of Conservation of Mass
  • To understand sources of error in labs


Notes


  • Every group takes out their lab procedures and reads them over.
  • The teacher randomly creates pairs and trios of groups.
  • Each group reads their procedures to the other group(s).
  • The groups discuss the similarities and differences between their procedures.
  • The groups create a single set of procedures, combining the best elements of their procedures.
  • The groups discuss possible sources of error in their procedures.
  • The groups choose a spokesperson who will report the procedures and sources of error to the class.

As a class, we will discuss the pros and cons of the procedures that were generated. Every group will then be given the chance to change their procedures to incorporate the best ideas that they have heard.


Lab

Run the lab using the sodium bicarbonate and vinegar provided by the teacher.

At the end of the lab, be sure to clean all your equipment by rinsing with water. It is safe to dispose of down the drain. Leave your equipment to drain on the drying racks at the back of the class.


Questions

You will need to use the Internet to find the answers to some of these questions.

  1. What is the chemical formula for the sodium bicarbonate (baking soda)?
  2. What is the chemical formula for the vinegar (weak acetic acid)?
  3. The chemical reaction between baking soda and vinegar proceeds in 2 steps. What are the balanced chemical reactions for these two steps?
  4. For each of the 2 steps, what is the type of reaction?
  5. Watch the following video of burning steel wool. What do you think will happen to the mass as it burns? What actually happens? Why?

    Burning iron wool and change in mass (1:28)


Assessment


  • Required Parts
    • Questions
    • Lab Report
      • Hypothesis
      • Materials (as a list)
      • Procedure (as a numbered list)
      • Data and Results
      • Analysis
      • Conclusion
      • Future Work
  • Design
    • Properly controlled experiment
  • Analysis, Questions, Conclusion, and Future Work
    • Do you have a clear explanation for your results? Can you link the lab to the theory?
    • Are your sources of error well identified?
    • Do you answer the questions correctly?
    • Does your conclusion answer the hypothesis?

Required Parts
 Design
 Analysis, Questions,
Conclusion, and
Future Work
1. Beginning Most

2. Developing - Poorly
controlled
 Some mistakes,
Simple answers
3. Applying ✓ ✓
 ✓
4. Extending - Clever
 Perceptive
answers