Adjust seating arrangement

1
Class Topics
Title Biology 9/27/07
Objectives

• To assess knowledge gained in chapter 2 test and
  begin learning about biochemistry

• Adjust seating arrangement
• Chapter 2 test
• There will be no potty breaks after the test
  PLAN ACCORDINGLY!
• Begin biochemistry!!!!!
• water
• If you make people think theyre thinking,
  theyll love you but if you really make them
  think, theyll hate you.
• Don Marquis

Handouts
Friday, November 06, 2009 727 AM
2
Class Assignments
By When
What

• Chapter 2 Test 9/27/07
• Binder Check 10/1/07
• All Chapter 2 homework corrections 10/1/07
• Read 49-51 10/1/07
• Due this class period
• Due next class period
• Due in the future

3
Move Desks

• Gather your materials in preparation to move to a
  new desk

4
Posttest activities

• Hand in the test in the appropriate tray
• Choose from the following
• Read 49-51
• Correct homework
• Read 49-51
• Read 49-51

5

• Water

• oxygen exerts a stronger pull on the shared
  electrons than hydrogen
• oxygen end
• slightly negative
• hydrogen end
• slightly positively
• Water is therefore a polar molecule

6
Nonpolar molecules

• No unequal sharing
• Do not dissolve in water
• Oils and fats

7
Characteristics

• Opposite charges attract
• This attraction forms hydrogen bonds
• Occurs with water and other molecules

Hydrogen bond
Figure 2.10A
8

• water exists in nature in all three physical
  states
• solid
• liquid
• a gas

Figure 2.10B
9

• Water in three different states

Figure 2.10Bx
10
Four Properties of Water

• Cohesion/Adhesion
• Ability to Stabilize Temperature
• Expansion Upon Freezing
• Versatility as a Solvent
• Video Clip The Shape of Water

11
Cohesion

• Cohesion
• Water molecules Stick together
• Water moves from a plants roots to its leaves
• surface tension
• Insects can walk on water
• Belly Flop!

Figure 2.11
12
Temperature moderation

• It takes a lot of energy to disrupt hydrogen
  bonds
• water is able to absorb a great deal of heat
  energy
• Small increase in temperature
• As water cools, a slight drop in temperature
  releases a large amount of heat

13

• A water molecule takes a large amount of energy
  with it when it evaporates

• This leads to evaporative cooling

14
Expansion upon freezing

• Ice is less dense than liquid water
• causes it to float
• What if ice sank?
• it would seldom have a chance to thaw
• Ponds, lakes, and oceans would eventually freeze
  solid
• Killing all living things

15

• Water, molecular model

Ice, molecular model
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Ice is less dense than liquid water

• Molecules in ice are farther apart than those in
  liquid water

Hydrogen bond
ICE Hydrogen bonds are stable
LIQUID WATER Hydrogen bonds constantly break and
re-form
Figure 2.13
17

• Ice fishing

Figure 2.13x1
18
Universal solvent

• Solutes whose charges or polarity allow them to
  stick to water molecules dissolve in water
• They form aqueous solutions

Na


Na


Cl
Cl





Ions in solution
Salt crystal
Figure 2.14
19
Review

• A compound that releases H ions in solution is
  an acid, and one that accepts H ions in solution
  is a base
• Acidity is measured on the pH scale
• 0-7 is acidic
• 8-14 is basic
• Pure water and solutions that are neither basic
  nor acidic are neutral, with a pH of 7

20
pH scale

• The pH scale

H
OH
Lemon juice gastric juice
Increasingly ACIDIC (Higher concentration of H)
Grapefruit juice
Acidic solution
Tomato juice
Urine
NEUTRAL H OH
PURE WATER
Human blood
Seawater
Neutral solution
Increasingly BASIC (Lower concentration of H)
Milk of magnesia
Household ammonia
Household bleach
Oven cleaner
Basic solution
Figure 2.15