Download Chemical Properties of Water

Chemical Properties
of Water
& Water Analysis
Chemical Properties of Water

CHEMICAL: defined as…



[Princeton U.]
relating to or used in chemistry;
produced by or used in a reaction involving
changes in atoms or molecules
of or made from or using substances produced by
or used in reactions involving atomic or molecular
changes.
Chemical Properties of Water
5
Key Factors:
Oxygen
CO2
Temperature
pH
Hardness
OXYGEN (Dissolved O2)
 Dissolved
(DO):
Oxygen
The amount of free
(not chemically
combined) oxygen
dissolved in water
 Most aquatic
organisms depend on
DO as their O2
source

OXYGEN (Dissolved O2)

Sources:



From water turbulence
(waves, waterfalls,
splashing on rocks, etc.)
From plants & algae
(photosynthesis)
From diffusion from air
OXYGEN (Dissolved O2)

Solubility of Oxygen:

Depends on temperature of water 
the colder the water, the more O2 it can
dissolve (see figure 5.1 pg.85 Blue Book)
Temp oC
Solubility (μg/g)
0
5
10
15
20
25
30
14.6
12.7
11.3
10.1
9.1
8.3
7.5
OXYGEN (Dissolved O2)

The Need for O2:

Aquatic species require different amounts of DO
 Trout, whitefish & walleye = high DO
 Carp, sunfish & catfish
= low DO
 Knowing

what you know…
Where would you fish for carp? For trout?
OXYGEN (Dissolved O2)

Factors that Remove O2:



Thermal Pollution
Respiration (especially
bacteria)
Algal blooms
Fecal Bacteria
Carbon Dioxide (CO2)

Need for CO2:
- for photosynthesis

Source of CO2:
- from the air
- from respiration

Removed By:
- plants
- turbulence
Temperature
Directly related to DO levels
 Increase temp. = lower DO, higher algae
growth, etc. (eutrophication)

pH

pH Scale:

A measure of acidity (or alkalinity)
Range of 0-14 (0-7 Acidic, 7-14 basic)

6.7–8.6 is desirable for fish (see fig.5-4 text)

pH

Eutrophication & pH:


As a lake ages, its pH will change over time.
Acid rain, pollution & sewage can alter pH
Oligotrophic
Mesotrophic
Eutrophic
Slightly Acidic
or Basic
More acidic
More Basic
Hardness
Caused by minerals in the water (calcium
& magnesium)
 Importance:


Supports living things, affects human health,
economic concerns.
LAB: Water Analysis




You have obtained 3 samples of
water – from 3 very different
sources.
Using the test kits, test the
chemical properties of these
water samples  1 per group.
Fill in the chart to record data
from 3 groups.
Now hypothesize the source of
these samples!
Get to it – The End!!