1. Today you will take a diagnostic pre-test for our next topic. Please remember that diagnostic tests do not contribute to your average BUT are very important because they help your teachers: (1) Understand how much you know about a topic before teaching begins. (2) Identify any misconceptions that you may have about a certain topic. (3) Assist you with setting learning goals. Please wait for Mr. Lastowski to give you directions for picking up your clicker and beginning the pre-test.

2. Chemistry Basics 1.Atomic Structure All things are made of atoms. The atom consists of a nucleus which contains protons, neutrons, and energy levels where the electrons are located. Please sketch the Bohr model of the carbon atom in your class notes: 2.Elements An element is a group of atoms with a distinct set of chemical and physical properties. More than 100 elements have been identified. The most important elements to living things are carbon, hydrogen, oxygen, and nitrogen. Information about the elements is summarized in the Periodic Table.

3. 3.Compounds When atoms of different elements share electrons they form a compound. A compound is made up of two or more elements that are chemically combined. A specific compound always has the same elements in the same proportion. For example, a water molecule always has two atoms of hydrogen and one atom of oxygen (water: H 2 O). COMMON COMPOUNDS NameMolecular Formula WaterH2OH2O AmmoniaNH 3 Carbon DioxideCO 2 Table SaltNaCl GlucoseC 6 H 12 O 6 Sucrose (table sugar)C 12 H 22 O 11

4. 4.Chemical Bonding Chemical bonding is the process by which compounds are formed. Bonding may be ionic (transfer of electrons) or covalent (sharing of electrons). Compounds formed by a covalent bond are called molecules. A molecule is the smallest part of a substance that has all the chemical properties of that substance.

5. Today you will take a safety test. As you walk in pick up your half sheet of paper you used yesterday and your clicker. Number the back of the paper from 1-20 and you will put your answers There and enter them in your clicker Please wait for Mr. Johnson to give you directions for picking up your clicker and beginning the pre-test.

6. P ROPERTIES OF W ATER 1.Water’s unique properties allow life to exist on Earth. 2.Water is a POLAR molecule.POLAR  POLAR molecules have slightly CHARGED regions.  Nonpolar molecules do not have charged regions.

7. 3.Hydrogen Bonds form betweenHydrogen Bonds slightly positive hydrogen atoms and slightly negative atoms. 4.Hydrogen bonds are responsible for several important properties of water:  High Specific Heat – hydrogen bonds require a high degree of heat before they break, minimizing temperature changes.  Cohesion – hydrogen bonds hold molecules of water together.Cohesiontogether  Adhesion – hydrogen bonds allow water molecules to “stick” toAdhesion other molecules.  Ice Formation – water molecules in an ice crystal are spaced relatively far apart because of hydrogen bonding. This explains why water expands as it freezes and why ice is less dense than liquid water.

8. 5.Many compounds dissolve in water. A solution is formed when one substance dissolves in another.  A solution is a homogeneous mixture (the same throughout).  Solvents (such as WATER) dissolve other substances.  Solutes (such as salt or sugar) dissolve in a solvent. 6.“Like dissolves like.”  Polar solvents dissolve polar solutes.  Nonpolar solvents dissolve nonpolar solutes.  Polar substances and nonpolar substances generally remain separate. Example: water and oil solution

10. The pH scale 1.pH is a measure of the hydrogen ions (H + ) in water. 2.An acid releases a hydrogen ion when it dissolves in water. Acids have a high H + concentration and a pH less than 7. 3.A base removes hydrogen ions from a solution. Bases have a low H + concentration and a pH greater than 7. 4.A neutral solution has a pH of 7.