1. Molecules & More
Unit 3 – Lecture 2

2. Discuss
Put the 9 levels of organization in order from smallest [atom] to largest [organism]

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

4. Molecules Molecule – composed of two or more atoms
can be made of a single element
or multiple elements
has no overall charge
example: H2 – two atoms of hydrogen
write this in: covalent bonding

5. Molecules – cont’d Compound – a molecule made of two or more elements
my abbreviation = cmpd(s)
MUST have more than one element present
Ex: H2O [2 atoms of hydrogen, 1 atom of oxygen]
ionic compounds have a positive or negative charge
Ex: NH4+
write this in: ionic or covalent bonding

6. What are the TWO major differences between a molecule and a compound?
Discuss
What are the TWO major differences between a molecule and a compound?

7. 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: H2O

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

9. Discuss
What is the major difference between a covalent bond and an ionic bond? [hint: it has to do with the electrons…]

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

11. 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

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

13. 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]

14. 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]

15. Discuss Explain the difference between: solute & solvent
hydrophilic & hydrophobic

16. 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]

17. 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.

18. 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

19. 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

20. 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

21. polar molecule [universal solvent]
Discuss
What four properties of water make it very important to living things? [answers below]
polar molecule [universal solvent]
high specific heat
hydrogen bonding
expands when frozen

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

23. 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: …?

24. 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.

25. Mixtures – cont’d Solution – a mixture that…
uses the term “solute” & “solvent”
solubility – the ability of a substance to dissolve in another

26. Discuss
Explain the difference between homogenous and heterogeneous mixtures.
Which type of mixture is a solution?

27. Homework Complete the first side of the Osmosis & Diffusion w/s
Finish the organelles worksheet – will be collected tomorrow.