Biology 102 A

1
Biology 102 A

• Properties of Water
• And
• Acids/Bases

2
Warm Up

• Your best friend thinks that fire is a living
  thing because it moves, needs oxygen and responds
  to wind.
• State your belief and give three reasons to
  support it.

3
. Living Things Use Need Energy a.)
energy comes from food, used to maintain body
b.) AUTOTROPH produce own food
c.) HETEROTROPH must consume food
d.) DECOMPOSER breaks down dead
material for food
4
. Living things respond to their surroundings
a.) they react to a stimulus b.) an action
causes a reaction c. ) reaction is called
a response d.) this involves one individual
5
Describe the properties of water that make it
important to living things.

• Water is polar it has an uneven distribution of
  electrons between the hydrogen and oxygen atoms
• One side of water is positive and the other is
  negative

6
Water properties

• Water is cohesive
• Cohesion attraction between same molecules,
  causes molecules to draw inward at surface
• Ex allows some insects spiders can walk on
  the surface
• Water is adhesive
• Adhesion attraction between different molecules,
  causes water to bend at the surface
• Ex capillary action-pulls column of water up to
  the top of a plant

7
Water properties

• Water is called Universal solvent dissolves
  many other substances due to polarity
• Differences in charges pulls/pushes substances
  apart
• Water exhibits evaporative cooling removes heat
  when it evaporates from a surface
• Ex sweating cools skin
• Water expands during freezing expands into
  crystal formation releasing heat
• Ex rocks broken up by ice creating soil ice
  layer protects fruit from freezing

8
Acids, Bases and the pH scale

• The pH scale measures the concentration of H
  ions (how acidic something is)
• Ranges from 0-14
• At 7 H ions and OH- ions are equal so it is
  neutral
• 0-7 acidic, has more H ions
• 7-14 basic, has more OH- ions

9

• ACIDS release H when mixed with water
• Sour, corrosive
• Ex HCl, H2SO4
• Always have H at front of formula
• BASES release OH- when mixed with water
• Bitter, slippery, usually in cleaners
• NaOH, CaOH
• Always have OH at end of formula

10
What is a buffer?

• Buffers are weak acids or bases that react with
  strong acids and bases to prevent sharp changes
  in pH
• Helps to neutralize
• Help to control pH in blood, digestive tract,
  etc. to maintain homeostasis

11
Reinforcement

• Your saliva measures 7 on the pH scale, it is
  a(n) ___ solution?
• a. acidic b. basic
  c. neutral
• The ___ property of water helps in the formation
  of soil.
• a. capillary action b. expansion during
  freezing c. evaporative cooling
• Laundry detergent typically has a pH of 3 which
  indicates a(n) ___ solution?
• a. acidic b. basic
  c. neutral
• The use of ___ helps to maintain a certain pH in
  our bodies maintaining homeostasis.
• a. buffers b. bases c.
  acids
• The ___ property of water removes heat helping to
  cool your skin through sweating.
• a. capillary action b. evaporation c.
  cohesion