Introduction to Chemistry, and Water

What are atoms?What are they made of?How do they interact with each other?

Water: How does it behave?Why does it behave so?

Why do we care?

chapter 2.1, 2.2, p 36-43

Hierarchy of Life

Atom, ← Molecule, ←

Organelle, Cell,

Tissue, Organ,

Organ system, Organism,

Population, Community,

Ecosystem, Biosphere.

Now we will start looking at these.

chapter

<Periodic Table Follows!>

DO NOT PANICThis is a pre-assessment. Please work alone.

For the elements chosen, name the subatomic particles,* how many of each there are, what charge they have, and what kind of atom you would have

if you added one more of each particle.*

(You will be handing this in.)

* The answers to these parts should be viewed asunderlined and emboldened.

This portion of the periodic tableshows the electrons, and their respective orbitals.

ELECTRONS

Major elements in living things:

- O, C, H, N and P together comprise 97% of your mass.

← notice these trace elements down here.

Covalent bonds

Two atoms are sharingelectrons, in order to establish full, morestable outer orbitals.

Ionic bonds:One atom gives up an electron to have its outermost orbital full

(resulting in a positive charge),And another gains an electron for the same reason

(resulting in a negative ion).As you know, opposites attract….

Emergent properties of compounds:

When two or more types of atoms join,the properties of the resultant compoundmay be entirely unlike those of the initial elements:

Below, sodium metal, poisonous chloride gas, and tasty sodium chloride.

What others come immediately to mind?

Properties of Water Atomic structure:

- Covalent bonds.- “Mickey Mouse” model of H2O: slightly positive at the “ears”,

and slightly negative at the “chin”.- Water molecules form weak hydrogen bonds due to this polarity….

> adhesionwater molecules ‘stick’ to other things

> cohesion water molecules ‘stick together’

> thermal propertieshigh specific heat (maritime effect in climate, cooling)

> expands on freezingmolecules less densely arranged in crystals than in fluid

> solubility‘like dissolves like’, means ionic solutes (salt)

and polar solutes (sugar) dissolve in polar solvent (water), and non-polar molecules (lipids) don’t,

[but will dissolve or suspend in non-polar solvent (alcohol)].

What is the biologic significance of each of these characteristics of water?

cohesion →← adhesion

combine to enablecapillary action ↓

← solubility → ↓

Biological Significance (cont.)

Hydrophobic oil in hydrophilic water:Relates to membrane structure…

Many solutes are transported in blood.

Even things like largeproteins can be dissolved.

thermal properties ↑↓

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Biological Significance (cont.)

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Acids and BasesFor our purposes,

an acid can form H+ in solution,while a base donates OH-,,

to make water.e.g.: 2NaOH + H2SO4 ↔ 2 H2O + Na2SO4

note: the arrow goes both ways…This is an equilibrium reaction.

pHThe pH scale indicates the relative amount of H+.

i.e., in neutral, distilled water,the concentration of dissociated H+ is 10-7 Molar(essentially one in 10-7 water molecules is H+ and OH- ),and the positive of the exponent is the “pH”,

or in this case, pH 7.If a base is reacting with those H+,

there will be fewer of them,and the pH goes… UP.

Think about it.

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note: - A high pH is a low H+ concentration.A high pH is a high OH- concentration.e.g. 10-4 [H+] solution has 10-10 [OH-].

- The scale reflects orders of magnitudei.e., pH 3 has 100 times the [H+] as pH 5.

Why do we care about acids and bases?

1. pH is an important influence on virtually all of your chemical reactions.e.g., Enzymes only work in a specific pH range.

2. Your blood pH tells your brain to make you breath.

3. Very strong stomach acids break down much of your food,then your intestines need to neutralize the acid.

4. Because pH is such an important part of homeostasis,you have weak acids and bases to buffer your system,

generally to pH 6.5 to 7.5.

Compare and contrast:covalent vs. ionic bonds

Compare and contrast:base vs. acid

What is an emergent property?Describe the chief emergent property of water,

and 5 effects that result therefrom.

Pick an element from a periodic table:Provide the number of each subatomic particle.Predict what type of bond it might form, and with what, and why?

Benchmark SC.912.L.18.12

Discuss the special properties of waterthat contribute to Earth’s sustainabilityas an environment for life:

cohesive behaviorability to moderate temperature,

expansion upon freezing,and versatility as a solvent.

Enduring Understandings

Essential Questions

How does water enable you to survive?

Water is an essentialcomponent of lifeas we know it

element hydrogen bond

proton polarity

neutron adhesion

electron cohesion

isotope thermal property

ion freezing

O (oxygen) solubility

C (carbon) capillary action

H (hydrogen) solute

N (nitrogen) hydrophobic

trace element hydrophilic

covalent bond acid

ionic bond base

emergent property equilibrium

compound buffer

adhesionmoleculecohesioncovalent bondhydrogen bondacidbasepHsolubility