Atomic Theory

“All things are made up of atoms.”

States of matter

Solid, liquid, gas, and plasma

State of Solids

  • Has definite shape and volume
  • High density and not very compressible
  • Does not depend on the shape of the container (doesn’t fill it in)

State of Liquids

  • Has a fixed volume
  • Takes the shape of container
  • Less dense than solids
  • Almost incompressible

State of Gases

  • Takes the shape of the container
  • Takes the volume of container (this means that the gas molecules can be spread out evenly in the container or compressed in a smaller container. The volume is when the molecules are evenly distributed.)
  • Can be compressed
  • Gases are in the gaseous state at room temperature
  • Gases have more energy than liquids, and solids.
  • Gases are less dense.

State of Plasma

Plasma is simply an ionized gas, where the gas is charged with free electrons and positive ions because of the amount of energy plasma contains.

Unit 1.4 – Heating and Cooling Curves

Heating and cooling curves are a graphical representation of the phase change of a substance. The heating curve of a substance can be determined by heating a solid slowly until it changes to the gas phase while a cooling curve of a substance can be determined by condensing a gas until a solid is formed.

The following curve is a heating curve for ice.
What do you notice?

heating curve

heating curve

Why is there a plateau?

  • In order for a solid to melt, energy is needed toovercome the intermolecular forces of attraction.
  • The heat that warms the ice is used to overcome these forces of attraction, rather than increasing temperature.
  • The temperature does not increase until all solid has disappeared.

What would happen if the temperature remained at the plateau?

  • There would be a constant change of states from liquid to solid and vice versa.
  • This is called dynamic equilibrium because there is an equal change.


Cooling curve of water

cooling curv

cooling curve energy