Download Grade 8 Science

Grade 8 Science
Unit 1:
Water Systems on Earth
Chapter 1
How do you use water?
House Hold Use
Personal Use
Recreational Activities
Water Distribution
 Only
3% of the Earth’s water is
fresh water (no salt).
 2/3 of this water is frozen in ice
sheets.
 Therefore only 1% of the fresh
water on Earth is available.
Lithosphere: the solid rocky
ground of the Earth’s crust.
Atmosphere: the
environment surrounding
the Earth.
Hydrosphere: All water on
Earth. Including that in the
lithosphere and atmosphere.
Why do we not run out
of water?
The Water Cycle...
The
constant cycling of
water through the
processes of evaporation
and condensation
Water is constantly
changing form
(gas
liquid)
Driven by the sun’s energy
Ocean Water vs. Fresh Water
Three ways in which fresh
water differs from ocean
water are:
Salinity
Density
Freezing point
1. Salinity
The
amount of salt
dissolved in a specific
amount of water.
* salt comes from
dissolved solids in the
ground and volcanoes.
2. Density
The
amount of mass of a
substance in a certain unit
volume.
How tightly packed
together the material is in a
substance.
The Dead Sea
3. Freezing Point
The
temperature at which a
liquid freezes.
Table
Fresh Water Salt Water
Salinity
Less salt
More salt
Density
Less dense
More dense
Freezing point Higher
(0˚C)
Lower
(-1.9˚C)
Scientists who study water...
1. Hydrologist:
A person
who studies Earth’s water
systems and helps to find
solutions to problems of
water quality and quantity.
2. Oceanographer: A
person who studies all
aspects of the ocean. They
are concerned with the
biology, geology, physics, and
mathematics of the ocean.
Sources of Fresh Water
Ground water
2. Glaciers
3. Drainage basins
1.
1. Ground water:
Precipitation that falls on
land and sinks out of sight.
Sinks
through
pores in rocks
until it reaches
bedrock where
it pools.
Drilling
to these pools
make wells.
Ground Water
2. Glaciers:
A
moving mass of
compressed snow and ice.
Found
in areas
where it is so
cold the snow
remains all
year.
Glaciers in
mountains and on
the continent of
Antarctica
 Glaciers
are reservoirs
(store fresh water)
 They
release the water during the
hot summer months.
 They
give us information about the
Earth’s past climates.
Water
trapped in
glacial ice
The Ice Age
Earth
has had at least 7.
 Most
recent:
120 000 years ago -11 000
years ago.
Covered from
the Arctic to as
far south as the
Great Lakes!
The environment was colder and a
lot of plants and animals went
extinct.
Glaciers and Global Warming
In
the last 100 years the
average surface temp. Has
increased by 0.5oC.
The world’s
glaciers are
melting at a
quicker
pace than
ever
before.
Receding Athabasca Glacier in Alberta
It has receded 1.5 km since 1843.
What does this mean?
Ocean
waters may rise
Flooding
3. Drainage Basins (aka. Watershed)
An
area of land from which
water drains into a body of
water (ex: river, pond, lake
or ocean).
 There
are
many small
drainage
basins within
a larger
basin.
Placemat Activity!
List or draw the species found in
freshwater environments
Freshwater
Environments:
 Lakes and ponds
 Wetlands
 Rivers and
streams
 Estuaries
P. 90-93
Saltwater
Environments:
Pelagic zone
(the water column)
 Benthic zone
(the ocean floor)

P. 94-95
Species examples
Vertebrates:
Invertebrates:
Microorganisms:
Plants:
Abiotic (non-living) factors that affect
plant and animal distribution:
1.
Temperature
Different species tolerate different
temperatures.
Lower temperature means better water
quality.
2.
Dissolved Oxygen
Colder water contains more dissolved
oxygen (better quality).
Dissolved oxygen levels should be at
least 5mg/L for good water quality.
3.
Phosphates
Essential nutrient for living things BUT too
much (from pollution) can be detrimental.
Phosphate levels should be less than 10μg/L
(micrograms/L) for good water quality.
4.
Increased acidity
Organisms have an acidity comfort-level and
can die if the water becomes too acidic.
pH should be
between 5 and 8.5
(on a scale of 1-14)
5. Turbidity – Cloudiness of the water
(how much dirt is stirred up) can affect fish's
ability to take up oxygen from the water. High
turbidity (very cloudy) means low water quality.
6.
Pollution
Point sources (specific source)
ex: landfill leak, factory waste
water
Non-point sources
(many sources)
ex: pesticides, runoff
from city streets
7.
Upwelling (marine only)
Vertical movement of water from the
ocean floor caused by wind on the
surface.
Stirs up nutrients
8.
Ocean Currents (marine only)
Currents affect on what lives where,
temperature, nutrients, and other factors.
9.
Salinity
The saltier the water is, the less plants and
animals will be able to survive in it. This
creates poor-quality ocean water (e.g. the
Dead Sea).