Environmental Science Test 1

Freshwater Textbook Sections 1 and 2

What atoms is a water molecule made of, and what charges do each of the atoms have?

2 hydrogen atoms and 1 oxygen atom. Hydrogen has a partial positive charge, oxygen has a partial negative charge.

Due to uneven electrical charge distribution between oxygen and hydrogen atoms…

Water is a polar molecule

What is the attraction between hydrogen of one molecule and oxygen of another?

This attraction is called a hydrogen bond.

Cohesion

Cohesion is the attraction between molecules of the same substance.

Adhesion

Adhesion is the attraction between molecules of different substances.

What causes surface tension?

Cohesion helps water stay connected, causing surface tension.

What is capillary action?

Adhesion draws water, pulling additional water molecules, allowing water to move against gravity.

Solvent

A substance capable of dissolving other substances.

Why is water an effective solvent?

Because of its polarity

How does water dissolve ionic compounds?

Water molecules attract and separate ions of an ionic compound, which makes it dissolve.

What does it mean to be hydrophilic, and what type of substances are usually hydrophilic?

Polar substances are usually hydrophilic, meaning that they quickly and willingly interact with water.

What does it mean to be hydrophobic, and what type of substances are hydrophobic?

Non polar substances are generally hydrophobic, meaning that they do not interact with water, such as oil.

Why is chemically pure natural water very rare?

When water moves, dissolved substances travel with it.

Why is water’s solid form less dense than its liquid form?

As water freezes, hydrogen bonds arrange the molecules into a structure that holds them farther apart.

What does density depend on?

The amount of mass in a given volume

Specific heat

The amount of energy required to change the temperature of a substance

Why does water have a relatively high specific heat?

Hydrogen bonds absorb energy as they break and release energy as they form, so added thermal energy is partially used to disrupt hydrogen bonds.

Does water tend to cool and heat slower or faster than other substances?

Slower, because of its high specific heat.

Reservoir

A location where water is stored within Earth’s system: the largest reservoir is an ocean, others include glaciers, groundwater, lakes, rivers, soil, the atmosphere, and even living organisms.

Evaporation

Liquid water from Earth’s surface to the atmosphere as water vapor

Transpiration

Water from soil to atmosphere through plants

Evapotranspiration

Combined movement of water to atmosphere through evaporation and transpiration

Advection

Water vapor moving horizontally through the atmosphere by moving air

Condensation

Water vapor turns into liquid droplets

Precipitation

Water from atmosphere returns to Earth’s surface

Sublimation

Solid water turns to water vapor, skipping over liquid

Deposition/Desublimation

Water vapor to solid water (ice)

Runoff

Precipitation reaches land, some water moves across surface

Infiltration

Precipitation reaches land, some water enters soil

Groundwater recharge

Water that moves downward enough to replenish groundwater

The water cycle

A network of reservoirs connected by processes that transfer water between them

Water molecules movement for solid ice

Molecules are held in an organized structure by hydrogen bonds, and molecules vibrate but are fixed in position.

Water molecules movement for liquid water

Molecules remain close but can move past each other; hydrogen bonds constantly form and break

Water molecule movement for water vapor

Molecules are farther apart and move freely

Are clouds made of water vapor entirely?

No! The visible portion of clouds is mostly billions of water droplets or ice crystals.

Adiabatic cooling

When rising air expands causing the air to cool

Dewpoint

Temperature at which water vapor begins to condense

How do condensation nuclei help form water droplets?

Water molecules collect on these airborne particles, forming water droplets

Orographic lifting

Air forced upwards over mountains

Ways air can rise

Air can rise from uneven heating, orographic lifting, or be lifted when air masses meet.

Cloud formation sequence

Air rises → air expands → air cools → water vapor condenses → cloud droplets form

Latent heat

Energy absorbed or released during a phase change

What phase changes absorb energy?

Evaporation, melting, and sublimation

What phase changes release energy?

Condensation, freezing, and deposition

Watershed

A watershed (drainage basin) is an area of land from which water drains towards a common outlet

Watershed divides generally follow…

Ridges and hills

Pathways for water entering a watershed

1. Precipitation → runoff → surface-water storage → evaporation or downstream flow

2. Precipitation → infiltration → soil-water storage → evaporation or plant uptake and transpiration

3. Precipitation → infiltration → percolation → groundwater recharge and storage → groundwater discharge

Water budget

Compares the amount of water entering and leaving a system

How to calculate water budget

Inputs - Outputs = Change in storage

Surplus

Inputs > outputs

Deficit

Outputs > inputs

Soil water budget

The water available in soil

Potential evapotranspiration (Ep)

The amount of water that could be transferred to the atmosphere through evapotranspiration if enough water were available

Actual evapotranspiration (Ea)

The amount of evapotranspiration that actually occurs

Recharge

Precipitation > water demand, so soil-water storage refills

Surplus

Soil-water storage reaches capacity, additional water available

Soil water usage

Depletion of stored soil water, precipitation does not provide enough water to meet plant and atmospheric demand

Deficit

Soil-water storage fully depleted, Ea < Ep

Soil water budget patterns in climates like Massachusetts

Recharge → surplus → usage → deficits → recharge

Permeable surface

A surface that allows water to infiltrate into the ground (usually soils and vegetated areas)

Impermeable surface

A surface that allows little or no infiltration (rooftops, paved surfaces)

What does more impermeable surfaces mean

More surface runoff, water reaches storm drains quickly

Stream discharge

Volume of flow per unit of time

Hydrographs

Hydrographs are graphs showing how stream discharge changes over time

When does stream discharge increase?

After a storm

Stream discharge in permeable lands

Stream discharge rises slower and reaches a lower peaks

Stream discharge in impermeable lands

Stream discharge rises quickly to a higher peak