Unit 8, Chapter 24

Integrated Science

Unit Eight: Water and the Environment

24.1 The Water Cycle

24.2 Water Quality

24.3 Acid Rain

24.4 Oceans

Chapter 24 Earth's Water Systems

Chapter 24 Learning Goals Describe the set of process through which water is

continuously recycled on Earth. Describe how water quality is analyzed. Understand the cause of acid rain. Understand the environmental effects of acid rain. Demonstrate the effect of acid on a natural ecosystem. Explain how the oceans were formed. Describe the composition of seawater. Explain how the oceans remove carbon dioxide from

the atmosphere. Discuss how toxic pollutants travel through marine

food chains.

Chapter 24 Vocabulary Terms precipitation producer reservoir salinity surface runoff surface water transpiration water cycle watershed

acid rain aquifer carnivore condensation evaporation food chain groundwater herbivore hydrosphere

24.1 The Water CycleThe amount of water on

Earth is about the same as it was during the age of the dinosaurs, 65 to 220 million years ago.

With about 70 percent of its surface covered with water, Earth is truly a water planet.

24.1 The Water Cycle Of the total amount of water on Earth, less than

1 percent is available for our consumption.Most is too salty or frozen as ice at the poles.

24.1 The Water Cycle

The four main processes of the water cycle are:— evaporation— transpiration— condensation— precipitation

24.1 The Water CycleAquifers contain groundwater.Groundwater that is not collected for our use will

continue to flow through sediments and eventually enter the ocean, thus continuing the water cycle.

24.1 Water ShedA watershed

is an area of land that catches all rain and snow and collects it one place like a river.

24.1 The Water CycleKey Question:

What is the quality of your local surface water?

*Read text section 24.1 BEFORE Investigation 24.1

24.2 Water QualityStandards are used to

judge water quality.

Water that meets these standards is safe for drinking, cooking, and other household activities.

24.2 Tap Water The variety and amount of ions in your tap water give

it a certain taste.

24.2 What's in your tap water?

24.2 Water Quality TestingTests that are performed:

— Water temperature— Dissolved oxygen test— Biological oxygen demand test— Turbidity test— Nitrate test— Phosphate test— pH test

24.2 Water QualityKey Question:

What is the quality of your tap water ?

*Read text section 24.2 BEFORE Investigation 24.2

24.3 Acid Rain

Any rain, snow, or fog that has a pH lower than 5.6 is called acid rain or acid precipitation.

24.3 Acid RainAcid rain is harmful

to natural environments because most life and life processes function in nearly neutral environments.

Acid rain reduces the amount of calcium in the soil.

24.3 Catalytic converterA catalytic converter

is a device that converts nitrogen oxide to nitrogen gas (N2) and oxygen (O2) before these emissions enter the atmosphere.

24.3 Acid RainKey Question:

What is acid rain?

*Read text section 24.3 BEFORE Investigation 24.3

24.4 Oceans

Oceans are part of the water layer of Earth’s surface, called the hydrosphere.

This layer covers much of its surface.

24.4 OceansEarth has five major oceans.

24.4 Six main ions in seawater

In addition, there are more than 70 additional trace elements that make seawater a very complex solution.

24.4 Salinity

The term salinity describes the “saltiness” of seawater.

Salinity describes how much salt is dissolved in one kilogram of water.

Salinity remains

constant.The salinity of the oceans has remained relatively constant for 600 million years because physical and chemical processes create a balance.

Calcium carbonate buffers the ocean.

More CO2 in the atmosphere could mean a more acidic ocean.

24.4 Carbon dioxide in the oceans

Energy and the Food ChainA food chain is a series of

steps through which energy and nutrients are transferred, from organism to organism, in an ecosystem.— Producers are plants and one-

celled organisms that concentrate energy from the sun through photosynthesis.

— Herbivores feed on producers.— Many carnivores, the next step

on a food chain, feed on herbivores.

A food chain can be represented as a pyramid, with producers forming the base, herbivores next, and carnivores at the top.

This arrangement represents how energy is lost in the food chain.

Decomposers recycle materials back to the food chain.

24.4 Energy loss in a food pyramid

As producers store energy, they also absorb small amounts of toxic pollutants in the water.

Next, herbivores eat large numbers of producers to obtain enough energy.

Top carnivores, who prey on other carnivores, can accumulate dangerous levels of toxic pollutants.

24.4 Toxins in pyramids

24.4 OceansKey Question:

How does carbon dioxide affect oceans?

*Read text section 24.4 BEFORE Investigation 24.4

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