1. Phases and Phase Changes

2. Solid
Has a definite shape and volume. Particles that make up a solid are packed together in relatively fixed positions and are held together by strong attractive forces between them.

3. Liquid
Has a definite volume but an indefinite shape (it assumes the shape of its container). Particles are close together but can move past one another. They move more rapidly than in a solid. This allows them to temporarily overcome the attractive forces and allows liquid to flow

4. Gas
Has neither a definite shape or volume. It will fill its container. Particles move very rapidly and are at great distances from each other. Attractive forces become very weak.

5. Physical Properties
Characteristics that can be observed or measured without changing the identity of the substance. They describe the substance.
Ex: Boiling point, Melting point

6. Physical Change
It does not involve a change in the identity of the substance.
Ex: Grinding, cutting, melting, boiling

7. Chemical Properties
Relates to a substance’s ability to undergo changes that transform it into different substances.
Easiest to see when substances react to form new substances.
Ex: Iron’s ability to rust, silver can tarnish when combined with sulfur

8. Chemical Change Also known as a chemical reaction
A change in which one or more substances are converted into different substances.

9. Drawing of Physical Change
Solid CO2 -> gaseous CO2

10. Drawing of Chemical Change
FeO2 -> Fe + O2

11. Density
Density depends on how tightly the atoms/molecules are packed together

12. Gas – low density
The molecules are far apart; therefore, lots of volume

13. Liquid – higher density
Molecules are closer together, so density is higher

14. Solutions – higher density
Water molecules have other molecules “fitting” into spaces, increasing the mass for the same volume
This is why sugar and salt water are more dense than pure water

15. Phase Changes Melting – changing from a solid to a liquid
Freezing – changing from a liquid to a solid
Evaporating – changing from a liquid to a gas
Condensing – changing from a gas to a liquid
Sublimation – changing from a solid to a gas
Deposition – changing from a gas to solid