Properties of Water for Pre-AP Biology

Cohesion

Attraction between water molecules due to hydrogen bonding (leads to surface tension, water droplets)

Adhesion

Attraction between water molecules and other substances (helps plants move up xylem)

High Specific Heat

Water absorbs/releases heat slowly →stabilizes climate and body temperature

High Heat of Vaporization

Takes a lot of energy to change liquid water into vapor →cooling effect (sweating, transpiration)

Density of Ice

Ice is less dense than liquid water → floats and insulates aquatic ecosystems.

Universal Solvent

Dissolves many substances (nutrients, gases, water) due to polarity

Melting and Freezing

Important in seasonal changes, affects organisms in lakes and soil

Evaporation

Removes heat energy, drives the water cycle

Condensation

Releases heat energy, forms clouds and precipitation

Sublimation and Deposition

Less common, but part of the cycle (ice→ vapor or vapor→ice)

;Biological Link: These changes regulate temperature and energy transfer in ecosystems and organisms.

Polarity

Water is a polar molecule → oxygen has a slight negative charge, hydrogens have a slight positive charge.

Polarity

Allows water molecules to form hydrogen bonds with each other and polar substances

Hydrologic (Water) Cycle

Processes:

Evaporation: (liquid → gas) from oceans, lakes, and soils.

Transpiration: Evaporation of water from plants.

Condensation: Water vapor → clouds

Precipitation: Rain, snow, hail returns water to Earth.

Runoff and Infiltration: Water moves into rivers, lakes, or groundwater

Biotic/Abiotic Cycling:

Biotic → water taken in by plants, animals, and microbes

Abiotic → lakes, rivers, glaciers, and atmosphere

Water moves between living things and the environment, transpiring nutrients and waste.

Biological Importance of Water

Solvent for Life: Dissolves salts, sugars, gases → allows chemical reactions in cells.

Nutrient Transport: In blood (animals) and sap (plants).

Temperature Regulation: Perspiration, transpiration, heat buffering.

Habitat: Aquatic ecosystems support life.

Key Vocabulary

Polar Molecule

Hydrogen Bond

Cohesion/Adhesion

Specific Heat

Heat of Vaporization

Hydrologic Cycle

Evaporation/Transpiration

Condensation/Precipitation

Solvent