Methane (CH4) Hydrogen (H2) Assist students who are having trouble building the Once you have completed your models, determine which molecules from the chemical formulas. molecule has a structure most similar to the sodium Students should identify potassium chloride as having a chloride. similar structure (linear composed of two different atoms) Mix the nuts and bolts in a small bowl. The nuts represent chlorine atoms, the bolts represent sodium atoms and the Facilitate group or class discussions which lead to an buttons represent water molecules. understanding of how the model for crystallization works. Discuss with your group how this model could be used to Students should understand that as water molecules show the crystallization of salt form during evaporation. (blue buttons) evaporated (removed) the chlorine atoms Use modeling clay and sticks to create a model of a large (nuts) and sodium atoms (bolts) move closer together. As salt crystal formed by evaporating salt water. they move closer together, they join to form crystals. As more water molecules are removed, more sodium and Sketch your model in the student lab sheets on page XX chlorine atoms join causing the crystals to grow. NOTE: Remind students that the shape of the sodium chloride crystal remains cubic no matter how big or small the crystal is. This is due to the atomic structure of the sodium chloride molecule. (This next portion will engage students in the Practice of Constructing explanations and designing solutions2) Ask students: Do you think it is possible to use this crystallization model for other compounds? Guide the student discussion to recognize that the model for potassium chloride has a similar number of atoms and has the similar linear shape, therefore it may have similar characteristics or properties as sodium chloride. As a result, students should recognize that this same process might be used in models that are similar in composition to sodium chloride such as potassium chloride.
Methane (CH4) Hydrogen (H2) Once you have completed your models, determine which molecule has a structure most similar to the sodium chloride. Mix the nuts and bolts in a small bowl. The nuts represent chlorine atoms, the bolts represent sodium atoms and the buttons represent water molecules. Discuss with your group how this model could be used to show the crystallization of salt form during evaporation. Use modeling clay and sticks to create a model of a large salt crystal formed by evaporating salt water. Sketch your model in the student lab sheets on page XX Assist students who are having trouble building the molecules from the chemical formulas. Students should identify potassium chloride as having a similar structure (linear composed of two different atoms) Facilitate group or class discussions which lead to an understanding of how the model for crystallization works. Students should understand that as water molecules (blue buttons) evaporated (removed) the chlorine atoms (nuts) and sodium atoms (bolts) move closer together. As they move closer together, they join to form crystals. As more water molecules are removed, more sodium and chlorine atoms join causing the crystals to grow. NOTE: Remind students that the shape of the sodium chloride crystal remains cubic no matter how big or small the crystal is. This is due to the atomic structure of the sodium chloride molecule. (This next portion will engage students in the Practice of Constructing explanations and designing solutions2) Ask students: Do you think it is possible to use this crystallization model for other compounds? Guide the student discussion to recognize that the model for potassium chloride has a similar number of atoms and has the similar linear shape, therefore it may have similar characteristics or properties as sodium chloride. As a result, students should recognize that this same process might be used in models that are similar in composition to sodium chloride such as potassium chloride.
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