1. 5.3 Properties and Phases of Matter
Our goals for learning
What is the structure of matter?
What are the phases of matter
How is energy stored in atoms?

2. Elements All matter is made up of elements.
An element is a substance that cannot be broken down into a simpler form by ordinary chemical reactions.
Over 90 elements occur naturally in the Earth.

3. Two properties of matter:
Physical – properties that can be observed or measured without a chemical reaction (ex. density, color, hardness)
Chemical- these describe how substances interact with other substances, to observe them requires a chemical reaction (iron & oxygen form rust)

4. What is the structure of matter?
All elements consists of atoms.
An atom is the smallest unit of an element that has all the properties of that element
Atoms of one element are different than that of another element

5. Subatomic particles- the parts of an atom
Three main types: electrons (-) protons (+) neutrons (neutral)

6. Nucleus- center of atom, contains protons, & neutrons
Electron cloud- region of space around the nucleus, contains electrons

7. Within the electron cloud, electrons are arranged in energy levels

8. An atom is mostly empty space.
Electron
Cloud
Atom
Nucleus
Use this figure to define the nucleus; protons, neutrons, electrons; scale of atom and “electron cloud.”
An atom is mostly empty space.

9. Atomic Terminology Atomic Number = # of protons in nucleus
Atomic Mass Number = # of protons + neutrons

10. The # of protons = the # of electrons in a neutral atom
Ion = an atom that has lost or gained electrons

11. Isotope: same # of protons but different # of neutrons. (4He, 3He)

12. What are the phases of matter?

13. Phases of the same material behave differently because of differences in chemical bonds
These are the bonds that hold atoms and molecules together

14. Changes in Matter
Ionization: Stripping of electrons, changing atoms into plasma
Dissociation: Breaking of molecules into atoms
Evaporation: Breaking of flexible chemical bonds, changing liquid into gas
(Condensation)
Melting: Breaking of rigid chemical bonds, changing solid into liquid
(Freezing)

15. Phase Diagram for Water

16. Phases and Pressure
Phase of a substance depends on both temperature and pressure
Often more than one phase is present

17. How is energy stored in atoms?
Electrons are restricted to particular energy levels
The lowest energy level is called the ground state
Higher energy levels are called excited states

18. The energy is measured in electron-Volts. 1 eV = 1.6 x 10 – 19 J
Excited States
Ground State
The energy is measured in electron-Volts.
1 eV = 1.6 x 10 – 19 J

19. Energy Level Transitions
The only allowed energy changes are those corresponding to a transition between levels
Electrons gain energy (by absorbing light) and jump to a higher level
Electrons lose energy ( by emitting light) and drop to a lower level
Not Allowed
Allowed

20. What have we learned? What are the phases of matter?
Adding heat to a substance changes its phase by breaking chemical bonds.
As temperature rises, a substance transforms from a solid to a liquid to a gas, then the molecules can dissociate into atoms
Stripping of electrons from atoms (ionization) turns the substance into a plasma

21. What have we learned? How is energy stored in atoms?
The energies of electrons in atoms correspond to particular energy levels.
Atoms gain and lose energy only in amount corresponding to particular changes in energy levels.