Assessment

Formative

Lab 1: Making Mixtures

Materials: Beakers, sand, salt, sugar, water, marbles

Procedure: Students work in groups and perform a series of experiments to understand the difference between pure substances, solutions and mixtures.

Example: Mixing sand or marbles with water will create a mixture, mixing sugar or salt with water will create a solution and water, sugar or salt on their own represent pure substances. Prior to creating the different mixtures students will be asked to Predict what will happen and then Observe & Explain. (Loughran, 2010)

Conclusions: By completing the experiments, students are expected to learn visually with hands on experience how to classify a pure substance, mixture and solution.

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Lab 2: Separating Mixtures 

Materials: Beakers, sand, salt, water, bunsen burner, evaporating dish, filter paper

Procedure: Working in groups, students mix salt, sand and water together. They will then Predict, Observe & Explain (Loughran, 2010) what will happen when using filter paper and the evaporating dish with their mixture. They will use the filter paper and a beaker to filter the mixture (separating the sand from the heterogenous mixture) and then the evaporating dish (separating the salt from the homogenous mixture).

Conclusions: In this lab the students will learn different ways of separating mixtures and understanding that the mixture of water and salt cannot be performed using filtration, thus it was a solution. Water was the solvent and salt the solute.The sand water mixture was heterogenous and not a solution.

Summative

A formal lab report can be submitted and questions related to pure substances & solutions should be included on a test or exam that covers the solutions unit.

Example Questions: 

• List 3 differences between pure substances and solutions
• What kind of mixture is a solution?
• Is Gold a pure substance or a mixture? Air? Oxygen? Water?

To be unique and more interactive you could have a physical test in which examples of solids, liquids or a gases are placed on desks around the room and have students move from station to station and decide if the object they are observing is a solution or not.

Example:

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Describe the following in terms of a pure substance or mixture:

A Brass instrument represents a solid solution of Zinc and Copper