 Everything in the universe is made up of matter. › Matter - anything occupying space and has mass.  Mass - amount of matter an object has.  Weight - force of gravity on a given mass. Q: Would your weight or mass change if you went to the moon?

 Elements - pure substances that cannot be broken down chemically into simpler kinds of matter. › 100+ elements have been discovered. › Less than 30 are important to living things. › Over 90% of the mass of living things consists of:  Carbon (C)  Hydrogen (H)  Oxygen (O)  Nitrogen (N)

 Periodic Table of Elements - lists information about each element including the element’s › Chemical symbol- 1-3 letters › Atomic number › Atomic mass

 Atom - simplest particle of an element that retains all of the properties of that element. Nucleus

 3 Subatomic Particles in Atoms › Proton - positively charged particle found in the atom’s nucleus. ATOMS OF AN ELEMENT ALWAYS HAVE THE SAME NUMBER OF PROTONS. › Neutron - Found within the nucleus and has no charge. › Electron - Small negatively charged particles with very little mass.  Move in orbitals found outside of the nucleus.

 Nucleus › Most of the atom’s mass › Contains protons and neutrons  Atomic Number = # of protons  Mass Number = # of protons + # of neutrons Q: How can you determine the number of neutrons an atom has? A: Mass number – Atomic number = # of neutrons

 Atoms have a net charge of ZERO. › # of Protons (+) = # of electrons (-)  Ex: (-2) + (+2) = 0  Orbital - region around nucleus telling us the probable location of an e- › Combination of all orbitals  electron cloud

 Orbitals and energy levels: › Each energy level relates to certain orbitals that can hold a set number of electrons.  1st energy level has 1 orbital- holds maximum of 2 e-  2nd energy level: 4 orbitals that hold 2 e- each (total of 8).

 Isotopes - Atoms of an element with a different number of neutrons (number of protons DOES NOT change). › Changes atomic mass

 media.discoveryeducation.com/videos/ Discovering the Elements/sec2941_300k.asf media.discoveryeducation.com/videos/ Discovering the Elements/sec2941_300k.asf

 Atoms of most elements readily combine with the same/different atoms or elements to make compounds.  Compound- atoms of 2+ elements in fixed proportions. › Ex: Water (H 2 O)

 Chemical and physical properties differ between compounds and the elements making them up.  Number and arrangement of e- determines how elements combine and form compounds. › Atoms are stable/less reactive when highest energy level is full. Ex: Noble gases

 Attractive forces holding atoms together. › Covalent Bond › Ionic Bond › Hydrogen bond

 Formed when 2 atoms SHARE one or more pairs of valence electrons.  Molecules - groups of atoms held together by covalent bonds.

 Transfer of e- from a metal atom to a nonmetal atom. › More stability for the atoms involved. › Creates ions (charged atoms that have gained/lost e-)

1. HCl 2. CO 2 3. Cl 4. Li 5. H 2 O HCl, CO 2, and H 2 O- compounds Cl and Li- elements

2.2

 1. water’s density enables life to exist under a layer of ice in freezing temperatures because ice floats. Water’s ability to absorb and retain heat helps moderate temperatures near large bodies of water. Water’s cohesive properties reduce its evaporation rate. Water’s adhesive properties enable it to overcome the force of gravity and travel upward (helpful in plants).

 2. Compounds that increase the concentration of hydronium ions in a solution are acids. Compounds that reduce the concentration of hydronium ions in a solution is a base. Acids have a pH less than 7. Bases have a pH above 7.

 3. Living things must maintain a stable pH. A buffer reacts with acids and bases to help keep pH stable in living things.  4. An organism’s internal temperature would likely change more abruptly and drastically in response to environmental temperature changes.

 5. The buffer reduces the acidity of the aspirin, which makes aspirin less irritating to the stomach.

 6. Each consecutive value on the pH scale represents a factor of 10. The lower the pH, the more acidic, and therefore the higher the concentration of hydronium ions. Therefore the concentration of hydronium ions in solution A is 100 times greater than the concentration in solution B.

 True or False: All solids will sink when dropped into a liquid.