DEMONSTRATION in Molarity. Last updated August 22, 2019.
In this demonstration, students will determine the molarity of several different solutions demonstrated by the teacher.
By the end of this lesson, students should be able to
- determine the molarity of several different solutions.
This lesson supports students’ understanding of
- Mole concept
Teacher Preparation: 5 minutes
Lesson: 20 minutes
- One of each of the following:
- 2000-mL beaker
- 1000-mL beaker
- 500-mL beaker
- 250-mL beaker
- 100-mL beaker
- 3 plastic cutouts of moles
- There are no special safety considerations for this lab.
- Before the demonstration:
- Gather beakers all supplies listed above.
- You may also use stuffed moles or plastic moles instead of paper cutouts.
- Have students finish the prelab questions and discuss the answers.
- For the demonstration:
- Demonstrate the mole concept by placing one mole in the one liter beaker and add water to the 1L mark. Indicate that this is a 1 Molar solution.
- Then move the mole into each of the other beakers filled with water and ask the students what the molarity of the new solution is.
- I repeat for the 2 mole situation by asking first which size beaker would be needed in order to create a 1 molar solution using 2 moles of solute. Then complete the process for that row.
- Repeat this process again for the 3 mole row. Begin again by asking what size beaker would be needed in order to create a 1 molar solution using 3 moles of solute.
- Finally rip one mole in half and repeat the process by placing the half mole in each of the beakers.
- Optional: Demonstrate making a 1 molar solution of salt using the correct technique in a volumetric flask.
For the Student
- What is a mole? ____________________________________________________________
- What is the mass of a mole of oxygen atoms? _________________________________
- What is the mass of a mole of water molecules? _______________________________
- A 1 molar solution is one in which ____ mole of any substance is dissolved in enough water to make up a total of ____ liter of solution.
- Molarity is defined as “a unit of concentration used in chemistry to indicate how strong or weak a solution is”. Its symbol is ______ and its units are ____________________________________.
As you watch the demonstration, fill in the molarity of each solution when either 1, 2, 3, or ½ moles is added to each beaker.
# of Moles
- Circle the correct answer within the ( ) for each statement below.
- The higher the molarity, the (more concentrated … less concentrated) the solution.
- The lower the molarity, the (fewer … greater) the number of particles the solution.
- Describe two ways to make a 0.5 molar solution.