Chapter 12 · Liquids, Solids, and Intermolecular Forces
12.1Spherical Water
7 min · two checks
Predict
Why do small water drops pull themselves into spheres?
The idea
- Separate intermolecular forces from bonds.
- Connect surface tension to inward pull.
Inside a water molecule, O–H bonds are strong covalent bonds. Between water molecules, the attractions are weaker intermolecular forces. They are strong enough, in water, to hold a drop together and to make the surface behave like a stretched skin. Insects that walk on a pond are standing on that skin, not on a chemical bond stretched across the pond.
This chapter is about those between-molecule forces and the states of matter they produce. If the forces are very weak compared with the temperature’s kinetic energy, the substance is a gas. If they are comparable, it is a liquid. If they lock particles in place, it is a solid. Changing the temperature changes the contest; it does not change the formula.
Keep these
- Bonds are inside molecules. Intermolecular forces are between them.
- Surface tension comes from inward intermolecular pull.
- State is a balance between kinetic energy and attractions.