Matter & Energy


Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Physical Properties of Liquids

.
E. Capillary Action

Water will climb up a paper towel if the edge of the towel touches a puddle, and it will climb up a thin glass tube if the tube is dipped in water. Water behaves this way because of an effect called capillary action. Capillary action occurs when the attraction of a liquid’s molecules for themselves differs from their attraction for a solid that the liquid contacts. The water in the paper towel example climbs the towel because the water molecules are more attracted to the paper than they are to each other.

Chemistry students demonstrate capillary action using a glass tube called a capillary tube and a beaker of water. Water climbs the glass tube when it is dipped in the beaker because the water is more attracted to the glass than it is to itself. Several forces are acting on the water: the attraction of the water molecules to the glass tube, the weight of gravity pressing down on the water in the tube, and the attraction of the water molecules for each other. The water rises in the tube until all these forces balance. For some liquids, such as mercury, the attraction between the molecules of the liquid is stronger than their attraction to the glass tube. When a glass tube is dipped in a beaker of mercury, capillary action makes the level of mercury in the tube drop below the level of mercury in the beaker.