Atoms and Molecules Caffeine molecule Macromolecule –a Protein

The atom –Neutral in charge. –Composed of nucleus with protons (+) and neutrons. –Electrons (-) found in energy levels around the nucleus. –Atoms are most stable when outer energy level is filled. Lithium: Atomic # = 3, Atomic mass = 6 Pair share: why are atoms neutral in charge if they are made of charged particles?

Compounds –Composed of atoms of two or more elements. –Held together by chemical bonds. – Chemical bonds require energy to form. –Chemical bonds result from outer electrons (valence electrons) interacting. Methane gas molecule CH 4 Remember: elements are specific types of atoms. The atomic # (# of protons) determines the identify of an atom. i.e. Hydrogen has 1 proton.

Types of bonds Covalent bondsCovalent bonds –Two or more atoms share electrons. –Covalent bonds form molecules. –Example: water Ionic bondsIonic bonds –Formed when electrons are transferred. –Atoms become charged (ions) –Opposite charged ions attract each other. –Example: salt Water: two hydrogen atoms plus an oxygen atom. Salt: one chlorine atom plus one sodium atom. Pair share: think of a memory device (mnemonic) to help you remember the difference between the 2 types of bonds.

Water: a special molecule Water is the most common molecule on Earth & in living organisms.Water is the most common molecule on Earth & in living organisms. Chemistry of living organisms takes place water.Chemistry of living organisms takes place water.

Structure of Water The Molecule H 2 0 is polar: it has a negative end and a positive end.H 2 0 is polar: it has a negative end and a positive end. –Oxygen is negative –Hydrogen is positive –Polarity makes water a good solvent.

Hydrogen Bonds Water molecules are attracted to each other.Water molecules are attracted to each other. (-) oxygen is attracted to (+) hydrogen.(-) oxygen is attracted to (+) hydrogen. The attraction is called a hydrogen bond.The attraction is called a hydrogen bond. Hydrogen bonds are very weak

Cohesion & adhesion Cohesion: Molecules of the same type are attracted to each other.Cohesion: Molecules of the same type are attracted to each other. –Surface tension is a result of cohesion. Adhesion: Molecules of different types are attracted to each other.Adhesion: Molecules of different types are attracted to each other. –Plants move water up stems in part due to adhesion. White board: why is this water bug not sinking?

High heat capacity of water Water must gain or lose a lot of energy for temperature to change.Water must gain or lose a lot of energy for temperature to change. Results in stable aquatic environment & the internal environment of cells.Results in stable aquatic environment & the internal environment of cells. Pair share: think about getting into a car on a hot day. Which part of the seatbelt do you grab ( the metal part or the cloth part)? Why? Remember the same about of energy is absorbed by both materials….

Energy –Ability to work or cause change. –Energy is never lost, it only changes form. –Different forms of energy. ChemicalChemical ThermalThermal MechanicalMechanical electricalelectrical Pair share: what type of energy do plants take in? How do they transform it?

Chemical Reactions Reactions have:Reactions have: –Reactants – starting chemicals –Products – ending chemicals 2 H 2 O 2 ---> 2 H 2 O + O 22 H 2 O 2 ---> 2 H 2 O + O 2 Photosynthesis Respiration

Reduction-Oxidation Reactions Don’t Panic!Don’t Panic! This is a fancy way to talk about electron transfers between products and reactantsThis is a fancy way to talk about electron transfers between products and reactants Oxidation: A substance gives up an electron and becomes more positiveOxidation: A substance gives up an electron and becomes more positive Reduction: A substance gains an electron and becomes more negativeReduction: A substance gains an electron and becomes more negative

White board Review 1.What is heat capacity? 2.What are the 3 particles that make up and atom? 3.What are the 2 types of chemical bonds.