water molecules. Additional emphasis should be placed Leave the beaker of salt on a window sill in in some place on how this process forms a homogeneous mixture that where maximum evaporation will occur for approximately 3 is impure substance. days. Explain to students that you will continue with the experiment in three to four days depending on when the water has evaporated. (This next portion will engage students in the Practice of Analyzing and Interpreting Data1) After 3 days, observe the contents of the beaker. You may After 3 or 4 days allow students to look at the contents of use a microscope or a hand lens to get a better view of the the beaker. They may use a microscope or hands lens to substance in the beaker. examine the crystals that have formed, or they may Record your observations in Table 1 of Student Lab Sheet. simply use the naked eye. Use the molecular model kits to build both the salt and the This next portion will engage students in the Practice of water molecules Developing and Using Models4) Instruct students to use the molecular model kits to build Sketch the salt and water molecules in the final column of salt and water molecules. They should then sketch the the Student Lab Sheet. molecules in the final column of Table 1 in their Student Lab Sheet. Emphasize that these sketches are types of Your teacher will lead a class discussion of the question models that help us to visualize the differences between found in the Student Lab Sheet. molecules (which are extremely small)of the two different pure substances. How did you make models that describe the composition of Engage students in a discussion about how molecular salt and water molecules? models were developed to describe the composition of the salt and water molecules. This will help them answer Write your answer to the question on the sheet based on to the question on page 1 of the Student Lab Sheet: the class discussion. How did you make models that describe the composition of salt and water molecules? Explain to students in Part 2 they will construct models of other pure substances to determine if they are similar to sodium chloride. They will also use a model to show how evaporation leads to the formation and growth of sodium chloride crystals.
Leave the beaker of salt on a window sill in in some place where maximum evaporation will occur for approximately 3 days. After 3 days, observe the contents of the beaker. You may use a microscope or a hand lens to get a better view of the substance in the beaker. Record your observations in Table 1 of Student Lab Sheet. Use the molecular model kits to build both the salt and the water molecules Sketch the salt and water molecules in the final column of the Student Lab Sheet. Your teacher will lead a class discussion of the question found in the Student Lab Sheet. How did you make models that describe the composition of salt and water molecules? Write your answer to the question on the sheet based on the class discussion. water molecules. Additional emphasis should be placed on how this process forms a homogeneous mixture that is impure substance. Explain to students that you will continue with the experiment in three to four days depending on when the water has evaporated. (This next portion will engage students in the Practice of Analyzing and Interpreting Data1) After 3 or 4 days allow students to look at the contents of the beaker. They may use a microscope or hands lens to examine the crystals that have formed, or they may simply use the naked eye. This next portion will engage students in the Practice of Developing and Using Models4) Instruct students to use the molecular model kits to build salt and water molecules. They should then sketch the molecules in the final column of Table 1 in their Student Lab Sheet. Emphasize that these sketches are types of models that help us to visualize the differences between molecules (which are extremely small)of the two different pure substances. Engage students in a discussion about how molecular models were developed to describe the composition of the salt and water molecules. This will help them answer to the question on page 1 of the Student Lab Sheet: How did you make models that describe the composition of salt and water molecules? Explain to students in Part 2 they will construct models of other pure substances to determine if they are similar to sodium chloride. They will also use a model to show how evaporation leads to the formation and growth of sodium chloride crystals.
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