water

Water is essential for life because of its unique chemical properties. Most environmental problems involving water come from:

·      Uneven distribution of freshwater

·      Overuse of groundwater and surface water

·      Pollution from human activities

·      Climate and population pressures

Water Molecule Basics

·      Water = H2O

·      Oxygen is more electronegative than hydrogen.

·      Water is a polar molecule:

o   Oxygen side = slightly negative

o   Hydrogen side = slightly positive

This polarity allows water molecules to attract each other.

Hydrogen Bonds

·      Weak attractions between the positive hydrogen of one molecule and the negative oxygen of another.

·      Individually weak, but collectively very important.

Why Hydrogen Bonding Matters

Hydrogen bonding gives water many special properties:

·      High specific heat

·      High heat of vaporization

·      Surface tension

·      Cohesion and adhesion

·      Ice floating on water

·      Excellent solvent ability

Possible Exam Questions

·      Why is water considered polar?

·      How does hydrogen bonding affect water properties?

·      Why does ice float

2. Phases of Water

Three Phases

·      Solid = ice

·      Liquid = water

·      Gas = water vapor

Phase Changes

·      Melting: solid → liquid

·      Freezing: liquid → solid

·      Evaporation: liquid → gas

·      Condensation: gas → liquid

·      Sublimation: solid → gas

Important Idea

Water absorbs or releases energy during phase changes.

3. Density of Water

Key Fact

·      Liquid water is denser than ice.

·      Ice floats because hydrogen bonds form a crystal structure that spreads molecules apart.

Why This Matters Environmentally

·      Lakes freeze from the top down.

·      Aquatic organisms can survive beneath surface ice.

Important Concept

Water reaches maximum density around 4°C.

4. Specific Heat & Heat of Vaporization

Specific Heat

Definition

The amount of energy required to raise temperature.

Water has a high specific heat.

Environmental Importance

·      Oceans moderate climate.

·      Coastal regions have less temperature variation.

·      Organisms maintain stable body temperatures.

Example

Land heats faster than water.

Heat of Vaporization

Definition

Amount of energy required to convert liquid water into vapor.

Water has a high heat of vaporization because hydrogen bonds must be broken.

Importance

·      Sweating cools the body.

·      Evaporation cools Earth’s surface.

5. Water as a Solvent

Why Water is Called the “Universal Solvent”

Because its polarity allows it to dissolve many ionic and polar substances.

Example

Salt dissolves because water surrounds sodium and chloride ions.

Importance

·      Nutrient transport in organisms

·      Chemical weathering

·      Pollution transport in water systems

Vocabulary

·      Solute = substance dissolved

·      Solvent = dissolving medium

·      Solution = mixture formed

6. Solutions and Solubility

Solubility

The amount of a substance that dissolves in a solvent.

Factors Affecting Solubility

·      Temperature

·      Pressure

·      Polarity

Important Idea

“Like dissolves like”

·      Polar substances dissolve in water.

·      Nonpolar substances do not dissolve well.

Environmental Relevance

Some pollutants dissolve easily and spread through groundwater.

7. Cohesion, Adhesion & Surface Tension

Cohesion

Water molecules stick to each other.

Cause: hydrogen bonding

Example

Water droplets forming.

Adhesion

Water sticks to other substances.

Example

Water climbing plant roots or paper towels.

Surface Tension

Strong cohesive forces at water’s surface.

Example

Water striders walking on water.

Importance

Helps water move through plants (capillary action).

8. Distribution of Water on Earth

Major Distribution

·      ~97% saltwater (oceans)

·      ~3% freshwater

Of freshwater:

·      Most is trapped in glaciers and ice caps

·      Much is groundwater

·      Very little is accessible surface water

Important Takeaway

Usable freshwater is extremely limited.

9. Water Use

Main Categories of Water Use

·      Agriculture (largest global use)

·      Industry

·      Domestic/municipal use

Consumptive Use

Water removed and not returned immediately.

Examples

·      Irrigation

·      Manufacturing

·      Household use

Problems from Overuse

·      Aquifer depletion

·      River depletion

·      Habitat destruction

WEEK 14 — HYDROLOGIC CYCLE & WATER ISSUES

10. Hydrologic (Water) Cycle

Definition

Continuous movement of water through Earth systems.

Main Processes

Evaporation

Liquid water → water vapor

Driven by solar energy.

Transpiration

Water released from plant leaves.

Evapotranspiration

Combined evaporation + transpiration.

Condensation

Water vapor cools and forms clouds.

Precipitation

Water falls as:

·      Rain

·      Snow

·      Sleet

·      Hail

Surface Runoff

Water flowing over land into rivers/lakes/oceans.

Infiltration

Water soaking into the ground.

Groundwater Flow

Water stored underground in soil and rock.

Important Concept

The hydrologic cycle redistributes water but does not create new water.

11. Surface Water

Definition

Water found above ground:

·      Rivers

·      Lakes

·      Streams

·      Wetlands

Problems

·      Pollution

·      Overwithdrawal

·      Habitat destruction

12. Groundwater

Definition

Water stored underground in pores and rock fractures.

Aquifer

Underground layer that stores/transmits water.

Recharge

Process where water infiltrates and refills aquifers.

Problems

·      Overpumping

·      Saltwater intrusion

·      Land subsidence

·      Contamination

Important Concept

Groundwater recharges slowly.

13. Water Scarcity & Shortage

Water Scarcity

Not enough accessible freshwater to meet demand.

Causes

·      Population growth

·      Climate change

·      Pollution

·      Overuse

·      Unequal distribution

Physical Water Scarcity

There is physically not enough water available.

Example

Arid regions with overuse of rivers and aquifers.

Economic Water Scarcity

Water exists but infrastructure/access is lacking.

Causes

·      Poverty

·      Poor management

·      Lack of technology

Important Difference

·      Physical scarcity = not enough water exists

·      Economic scarcity = water exists but people cannot access it

14. Water Withdrawals

Water Withdrawal

Removal of water from surface or groundwater sources.

Main Uses

·      Agriculture

·      Power generation

·      Industry

·      Municipal use

Agriculture

Largest freshwater withdrawal globally.

Irrigation Problems

·      Salinization

·      Wasteful water loss

·      Aquifer depletion

15. Global Water Use

Global Trends

·      Increasing population increases water demand.

·      Agriculture dominates freshwater use.

·      Some regions experience severe shortages.

Key Point

Freshwater availability is unevenly distributed.

WATER POLLUTION

16. Water Pollution Basics

Definition

Any contamination that degrades water quality.

Major Categories

·      Chemical

·      Biological

·      Physical

17. Chemical Pollution

Examples

·      Heavy metals (lead, mercury)

·      Fertilizers

·      Pesticides

·      Oil

·      Industrial chemicals

Effects

·      Toxicity

·      Bioaccumulation

·      Ecosystem damage

Nutrient Pollution

Excess nitrogen and phosphorus cause algal blooms.

Eutrophication

Nutrient enrichment leading to oxygen depletion.

Consequences

·      Fish kills

·      Dead zones

18. Biological Pollution

Examples

·      Bacteria

·      Viruses

·      Parasites

Sources

·      Sewage

·      Animal waste

Effects

·      Waterborne disease

·      Unsafe drinking water

Examples of Diseases

·      Cholera

·      Dysentery

19. Physical Pollution

Examples

·      Sediment

·      Trash/plastics

·      Thermal pollution

Thermal Pollution

Temperature increase from industrial discharge.

Effects

·      Lower dissolved oxygen

·      Stress on aquatic organisms

20. Natural vs Anthropogenic Sources

Natural Sources

·      Volcanic activity

·      Sediment erosion

·      Natural oil seepage

Anthropogenic (Human-Caused) Sources

·      Industry

·      Agriculture

·      Urban runoff

·      Sewage discharge

·      Mining

Important Exam Point

Most severe modern water pollution problems are anthropogenic.

WATER MANAGEMENT

21. Watershed Management

Watershed Definition

Land area draining into a common water body.

Goal of Watershed Management

Protect water quality across an entire drainage basin.

Strategies

·      Reduce runoff

·      Prevent erosion

·      Protect wetlands

·      Limit pollutants

22. Regulations & Water Protection

Goals of Water Regulations

·      Protect drinking water

·      Reduce pollution

·      Improve ecosystem health

Examples of Approaches

·      Wastewater treatment

·      Pollution limits

·      Monitoring programs

·      Conservation policies

23. Water Solubility (Possible Essay Topic)

Key Concepts to Explain

·      Water is polar.

·      Polar water molecules dissolve ionic/polar substances.

·      Water surrounds ions and separates them.

Why It Matters

·      Nutrient transport

·      Biological processes

·      Pollutant movement in groundwater and rivers

Strong Short-Answer Example

“Water is an excellent solvent because it is polar. The partially negative oxygen and partially positive hydrogens attract ions and polar molecules, allowing many substances to dissolve. This is important because it allows nutrients and pollutants to move through ecosystems and living organisms.”

24. Bangladesh Water Crisis

Main Issue

Groundwater contamination with arsenic.

Cause

Tube wells drilled to avoid pathogen-contaminated surface water tapped arsenic-rich groundwater.

Effects

·      Arsenic poisoning

·      Skin lesions

·      Cancer

·      Long-term health problems

Important Lesson

A solution to one environmental problem can create another.

25. East Palestine (Ohio Train Derailment)

Main Issue

Chemical contamination after hazardous train derailment.

Concerns

·      Toxic chemicals entering waterways and soil

·      Air and water contamination

·      Long-term ecosystem and health impacts

Important Themes

·      Industrial accidents

·      Water contamination risks

·      Emergency response challenges

26. Chesapeake Bay

Main Problem

Nutrient pollution causing eutrophication.

Sources

·      Agricultural runoff

·      Fertilizers

·      Sewage

Effects

·      Algal blooms

·      Hypoxia (low oxygen)

·      Dead zones

·      Fish and crab population decline

Solutions

·      Reduce nutrient runoff

·      Better wastewater treatment

·      Watershed management

27. Cuyahoga River

Historical Significance

River became heavily polluted from industrial waste.

Famous Event

River caught fire multiple times due to oil and pollution.

Importance

Helped inspire stronger environmental regulations in the United States.

Lessons

·      Industrial pollution can severely damage waterways.

·      Public awareness can drive environmental policy change.

HIGH-YIELD COMPARISONS

Cohesion vs Adhesion

Physical vs Economic Water Scarcity

Surface Water vs Groundwater

Chemical vs Biological vs Physical Pollution

Must Know Definitions

·      Hydrogen bond

·      Solubility

·      Specific heat

·      Heat of vaporization

·      Cohesion

·      Adhesion

·      Surface tension

·      Aquifer

·      Water scarcity

·      Eutrophication

·      Watershed

Must Know Concepts

·      Why water is polar

·      Why ice floats

·      Why water moderates climate

·      Difference between physical and economic water scarcity

·      How eutrophication happens

·      Difference between surface water and groundwater

·      Human causes of water pollution

RAPID REVIEW QUESTIONS

1.        Why does water have high surface tension?

2.        Why is water an effective solvent?

3.        Why does ice float?

4.        What is the difference between cohesion and adhesion?

5.        What is an aquifer?

6.        What causes eutrophication?

7.        Difference between physical and economic water scarcity?

8.        Why is groundwater depletion a problem?

9.        What are major sources of water pollution?

10.  Why is agriculture such a large user of freshwater?