1. Unit 3 – Lecture 2

2. Levels of Organization – review Atom Molecule Biomolecule [aka macro- molecule] Organelle Cell Tissue Organ Organ system Organism

3. Molecules Molecule – composed of two or more atoms can be made of a single element or multiple elements has no overall charge example: H 2 – two atoms of hydrogen

4. Molecules – cont’d Compound – a molecule made of two or more elements my abbreviation = cmpd(s) MUST have more than one element present Ex: H 2 O [2 atoms of hydrogen, 1 atom of oxygen] ionic compounds have a positive or negative charge Ex: NH 4+

5. Molecules – cont’d Types of Bonds Covalent Bonds formed when atoms share valence electrons “co” – together valence electron – electron in the outermost shell of an atom a strong bond Ex: H 2 O

6. Molecules – cont’d Types of Bonds Ionic Bonds formed when atoms gain or lose electrons by transfer weaker than a covalent bond Ex: NaCl

7. Properties of Water Approximately 2/3 of your body is water…so apparently it’s quite important… What makes water so important??

8. Water is a Polar Molecule Polar Molecule: has no overall charge [hence… “molecule”] but has a side that is more electronegative electronegativity – the ability of an atom to attract electrons to itself uneven distribution of electrons leads to a negative pull on one side

9. Water is a Polar Molecule The oxygen side of the molecule is much more electronegative than the hydrogen side

10. Water is a Polar Molecule It is the “Universal Solvent” water given this term because it is able to dissolve many substances this is because of its polarity solvent: a substance that is used to dissolve a solute. solute: a substance that is dissolved by the solvent Ex: water [solvent] dissolves sugar [solute]

11. Water is a Polar Molecule Polar is aka Hydrophilic hydrophilic: literally, “water-loving” “hydro” = water “philos / phil / philia” = to love dissolve easily in water [like sugar] hydrophobic: literally, “water- fearing” “phobia / phobic / phobos” = to fear aka non-polar do not dissolve or mix easily in water [like lipids]

12. Water Performs H-Bonding Hydrogen Bond: bond formed between a H and a more electronegative atom is very weak is not a true “bond” but an attraction usually takes place between oxygen [O], nitrogen [N], or fluorine [F]

13. Water Performs H-Bonding Adhesion – the ability of water to form H-bonds with other molecules [to “stick” to other things ] think “adhesive” ex: straw in water water climbs above the surface level aka capillary action major way blood flows through the capillaries in your body and through the roots of plants.

14. Water Performs H-Bonding Cohesion – the ability of water to form H-bonds with other water molecules causes surface tension Ex: water drops form small spheres, can overfill a glass, some bugs can walk on water

15. Water Expands when Freezing is less dense when frozen; most substances are more dense allows it to float on water when frozen if ice sunk, lakes & ponds would freeze solid in winter

16. Water has a High Specific Heat Specific Heat – amount of energy it takes for the temperature of a substance to increase or decrease makes homeostasis MUCH easier

17. Mixtures Mixture – a combination of multiple substances that… can be physically separated are not combined chemically can be homogenous or heterogenous

18. Mixtures – cont’d Mixtures can be homogenous or heterogeneous homogenous – appearance and consistency are the same throughout “genous” – type typically called solutions heterogeneous – appearance & consistency are different throughout Ex: …?

19. Mixtures – cont’d Solution – a mixture that… is homogenous is in a single phase solid, liquid, or gas can have different phases dissolved in one another gas in liquid [carbonated water] solid in solid [alloys – carbon/iron = steel; copper/zinc = brass] solid in liquid [sugar water] etc.

20. Mixtures – cont’d uses the term “solute” & “solvent” solubility – the ability of a substance to dissolve in another