M ORE S IXTH G RADE R EVIEW Water and its roles in the natural and human- made environment

W ATER Water is the only compound that commonly exists in all three states (solid, liquid, gas) on Earth. The unique properties of water are a major factor in the ability of our planet to sustain life. The addition of heat is responsible for water changing from the solid state to the liquid state and finally to the gaseous state. Removing heat will reverse the process.

W ATER ’ S DENSITY Liquid water has a density of 1.0 g/ml Cold water is denser than warm water From 4° to 0° ice expands about 9%, this accounts for the force of ice in nature C water is in the liquid phase Solid water is less dense that liquid water

ADHESIVE AND COHESIVE PROPERTIES OF WATER. Water is attracted to other water. This is called cohesion. Water can also be attracted to other materials. This is called adhesion. Surface tension is the cohesion of water molecules at the surface of a body of water.

W ATER M OLECULE When a water molecule is slightly negative and another water molecule is slightly positive they can stick to each other Individual water molecules, therefore, attract other water molecules like little magnets as the slightly positive portion of a water molecule is attracted to the slightly negative portion of an adjacent water molecule.

U NIVERSAL S OLVENT A large number of substances will “dissolve” in water. For this reason, water is often called the universal solvent.

W ATER AND ENERGY The ocean is the largest reserve of heat on the earth. Why?

O CEAN C LIMATE C OMPARISON How are the two cities different in climate? What causes the main difference?

O CEAN C LIMATE COMPARISON II Which city is near a big body of water? How can you tell?

O CEANS A FFECT ON W EATHER

W ATER AND CLIMATE Large bodies of water act to moderate the climate of surrounding areas by absorbing heat in summer and slowly releasing that heat in the winter. The climate near large bodies of water has less drastic changes. Example: our summer/winter compared to Richmond/Williamsburg.

W ATERS CHANGING STATES

G LOBAL W ARMING The earth NATURALLY goes through warming and cooling cycles (global warming and ice ages). Humans do not cause this, however; we do not want to add to the cycle either to avoid the ‘pendulum swing’ from being severe.

W ATER ’ S AFFECT ON THE ENVIRONMENT Water (rain, ice, snow) has shaped our environment by physically and chemically weathering rock and soil and transporting sediments

W EATHERING Freezing water can break rock without changing any minerals that make the rock (Physical weathering) makes sand. Water with dissolved gases and other chemicals causes the minerals in rocks to change (chemical weathering).

T HE EARTH ’ S WATER Most of Earth’s water is salt water in the oceans (97 percent). Fresh water makes up 3% and with most of it being frozen, less than 1 percent of the water on Earth is useable drinking water.

W HERE IS ALL THE EARTH ’ S WATER Water occurs on Earth in oceans, lakes, rivers, streams, and in rock layers underground called aquifers

A LARGE AMOUNT OF WATER IS ALSO FOUND IN THE BODIES OF LIVING THINGS.

W ATER IS ESSENTIAL FOR AGRICULTURE. C ROPS WATERED BY RELIABLE IRRIGATION SYSTEMS ARE MORE PRODUCTIVE, AND HARVESTS MORE DEPENDABLE.

M AKING OF ELECTRICITY WITH WATER

W ATER T REATMENT Advances in water treatment and sanitary sewers have helped eliminate diseases associated with human waste.

E COSYSTEMS Abiotic = NOT LIVING Abiotic factors determine ecosystem type and its distribution of plants and animals as well as the usage of land by people. Abiotic factors include water supply, topography, landforms, geology, soils, sunlight, and air quality/O 2 availability.

A N ECOSYSTEM IS MADE UP OF THE LIVING COMMUNITY AND THE NONLIVING FACTORS THAT AFFECT IT. The health of an ecosystem is directly related to water quality.

H UMAN ACTIVITIES CAN ALTER ABIOTIC COMPONENTS AND THUS ACCELERATE OR DECELERATE NATURAL PROCESSES People can affect the rate of erosion. Plowing cropland can cause greater erosion, while planting trees/plants can help prevent it.

W ATERSHEDS A watershed is the land that water flows across or through on its way to a stream, lake, wetland, or other body of water. Areas of higher elevations, such as ridgelines and divides, separate watersheds.

V IRGINIA ’ S W ATERSHEDS The three major regional watersheds systems in Virginia lead to the Chesapeake Bay, the North Carolina sounds, or the Gulf of Mexico.

R IVER SYSTEMS River systems are made up of tributaries of smaller streams that join along their courses. The wide, flat, border areas on both sides of a river are called flood plains, where water has risen due to high levels of water.

D EPOSITION IN RIVERS Rivers and streams carry and deposit sediment. Faster water = more sediments in the load. Slower water drops out sediments as it slows down.

W ETLANDS Wetlands exist between dry land and bodies of water such as rivers, lakes, or bays. Wetlands’ purposes include regulating runoff by storing flood waters; reducing erosion by slowing down runoff; maintaining water quality by filtering sediments, trapping nutrients, and breaking down pollutants; and recharging groundwater.

ESTUARIES Estuaries are areas where salt water and fresh water mix. Ex. Chesapeake Bay (largest in world) and Back Bay Estuaries provide habitats for many organisms and serve as nurseries for their young.