Around the house
The chemistry and electric forces behind washing, deposits and changing surfaces.
- Why does sugar stop dissolving in tea? At a given temperature, a fixed amount of water can hold only so much dissolved sugar at equilibrium. Once the solution is saturated, extra sugar can remain as crystals.
- How does soap remove grease? Soap molecules have regions that interact differently with water and grease. This structure helps loosen and disperse oily material so that rinsing can carry it away.
- Why does a kettle develop a white crust? Heating hard water can cause dissolved substances to form solid calcium carbonate deposits. Water can look completely clear before those mineral deposits appear.
- Why can scratched paint lead to rust? A scratch exposes iron to water and oxygen. Electrochemical reactions then transform some of the metal into rust.
- Why does a rubbed balloon attract paper? Rubbing can leave a balloon electrically charged. Its charge slightly shifts the distribution of charges in nearby neutral paper, allowing attraction to outweigh repulsion.