Liquid Crystals and Electronic Calculators

different colors appear.

Liquid crystals are also used for the display in electronic calculators. When we press a button on the calculator, we send an electric current through the display. The electric current causes molecules in the liquid crystal to change their positions. More or less light passes through the crystal, and numbers either light up or go dark. The motion of the particles of matter is a function of the energy they contain. Suppose that we add heat, a form of energy, to a solid. That heat is used to increase the speed with which the solid particles are moving. If enough heat is added, the particles eventually move rapidly enough that the substance turns into a liquid: it melts.

One can distinguish among solids, liquids, and gases on two levels: the macroscopic and submicroscopic. The term macroscopic refers to properties that can be observed by the five human senses, aided or unaided. The term submicroscopic refers to properties that are too small to be seen even with the very best of microscopes. On the macroscopic level, solids, liquids, and gases can be distinguished from each other on the basis of shape and volume. That is, solids have both constant shape and constant volume. Liquids have constant volume but indefinite shape. Gases have neither constant volume nor constant shape. They take the size and shape of whatever container they are placed into.

These macroscopic differences among solids, liquids, and gases reflect properties of the particles of which they are made. In solids, those particles are moving very slowly and tend to exert strong forces of attraction on each other. Since they have little tendency to pull away from each other,