Molecules and Volume - Does 3 + 3 = 5? (Dave Farina)
Author
Carol Cao
Principle(s) Illustrated
Molecular Packing
Volume
Molecular Structures
Standards
Chemistry-Chemical Bonds
2f Students know how to predict the shape of simple molecules and their polarity from Lewis dot structures.
2d Students know the atoms and molecules in liquids move in a random pattern relative to one another because the intermolecular forces are too weak to hold the atoms or molecules in a solid form.
Questioning Script
Prior knowledge & experience:
Ionic and Covalent Bonds
Intermolecular Forces
Molecular Structures
Root question:
When two liquids of equal volume are added together, is the resulting volume equivalent to adding the two original volumes together? Will 50mL of one liquid + 50mL of another liquid equal 100mL?
Target response:
No. Adding two equal volumes of two different liquids does not have to be equal to simple addition. Different molecules of substances will molecularly pack differently and fill spaces that weren't there before. When you add 50mL of alcohol and 50mL of water, the resulting new volume will be less than 100mL.
Common Misconceptions:
One common misconception is that the volume will be 100mL because when you add 50mL to 50mL , then clearly that results in 100mL.