Science Chemistry Unit
Review Lab safety and WHMIS symbols
Matter
is anything that has mass and occupies space.
Matter can be described using chemical and physical properties.
Light and heat energy is NOT matter because it is not made up of particles.
Physical properties
are those that can be observed or measured. For example, state, color, density.
Know the different physical properties in Table 1.1 on page 18.
Chemical properties
are whether a substance can react with another to form a new product. Know
the different chemical properties in Table 1.2 on page 19.
Theories vs Law
Laws
are descriptions of events or patterns that have been observed over and over
again. Laws do not provide explanations, they simply state what happens. Laws
are the same throughout time.
Theories
are explanations of observations that are supported by evidence. Theories can
change as new information become available.
Atomic Theory
All matter is composed of particles called atoms.
(Everything you learned about the particle theory holds true in the atomic
theory.)
What is an atom?
Atoms are composed of particles including protons, electrons and neutrons.
Atoms have a tiny positive nucleus made up of protons and neutrons.
Surrounding the nucleus are negatively charged electrons in specific energy
levels.
Development of the Atomic Theory
Dalton (John)
- Proposed matter was made of small, hard spheres that are different for
different elements. See Dalton’s Atomic Theory page 26
Thomson (J.J)
-
Discovered electrons
Proposed the “raison bun” model
Atoms were positive charged balls (like the bun) with negative charges
embedded in it (like the raisons)
Rutherford (Ernest)
-
Discovered the nucleus
Proposed that atoms were mostly “empty Space” with electrons moving
about the nucleus.
- He later proposed that the nucleus contained protons and neutrons.
(see text page 27 to review his famous gold foil experiment.)
Bohr (Niels)
-
Proposed that electrons surround the nucleus in specific energy levels or
electron shells.
Each electron has a particular amount of energy.
3 Subatomic Particles
Protons – positive charges found in the nucleus of the atom
Neutrons – neutral particles found in the nucleus.
Electrons – negative charged particles found in energy levels (shells)
surrounding the nucleus.
The nucleus contains the most mass in an atom. Electrons occupy the most
space (volume) in an atom.