10 Science Principles You See in Action Every Day

#8

Classical States Of Matter:

Four states of matter are observable in everyday life: solid, liquid, gas, and plasma. 

Each one is defined by major physical characteristics, determined in large part by the kinetic energy of molecules as well as attractive forces [source: Kurtus]. The temperature or energy determines which force wins. The higher the temperature of the molecules, the greater the kinetic energy and the faster the molecules will move.

You can see this in action by starting with a glass full of ice cubes, representing the solid state when the molecules are confined to vibrating either in place or in rotation. As the ice melts, the molecules gain enough kinetic energy to overcome the force until it becomes liquid.


If the water is boiling (or else in a very reduced pressure), the molecules are extremely energetic and their kinetic energy is greater than the attractive force between them. Thus, the water will become gas and spread beyond an open container [source: Kurtus]. The water will ultimately evaporate, though it evaporates more slowly at freezing point than boiling point because the energy required to break up the bonds holding water molecules together happens more quickly with the latter option [source: United States Geological Survey].

Terms:

solid:

A substance that retains its size and shape without a container; a substance whose molecules cannot move freely except to vibrate.

Liquid:

A substance that flows and keeps no definite shape because its molecules are loosely packed and constantly moving. It takes the shape of its container but maintains constant volume.

Gas:

A substance that can only be contained if it is fully surrounded by a container (or held together by gravitational pull); a substance whose molecules have few inter molecular bonds and can move freely.