Properties of H2O

per Ms. Jones lecture notes

H2O is Cohesive

Water molecules are attracted to each other due to hydrogen bonding, causing them to stick together and create surface tension

• allows organisms to move on water as it causes the water to resist an external force

H2O is Adhesive

The polar nature of water molecules and the resulting hydrogen bonds they form with other polar or charged molecules causes water to stick to other surfaces or substances.

• however, cannot stick to nonpolar or waxy surfaces/substances

H2O is used for photosynthesis

Plants use water and carbon dioxide to provide the earth food and oxygen, which is vital for life.

• vascular tissue (xylem) acts as a pipeline for water and mineral transport from the roots to the rest of the plant

• In narrow tubes like the xylem, the adhesive forces between water and the tube walls, combined with the cohesive forces between water molecules, can cause water to move upward against gravity towards the leaves (capillary action)

H2O has high heat capacity

Water can absorb a lot of heat before the temperature increases as it requires a lot of energy to change its temperature.

• This is due to the hydrogen bonds between water molecules, which require energy to break and reform

H2O has evaporative cooling

When water evaporates, heat energy is released, cooling the water left behind. This occurs because water molecules require heat to transition from a liquid to a gaseous state (evaporate).

• perspiration (sweating) and evaporation cools the body and regulate temperatures

H2O expands when it cools

When frozen, water spread out into crystals and insulates water below it, usually floating on top of the water surface as ice is less dense.

H2O is a universal solvent

Water dissolves more substances than any other liquid, due to its unique molecular structure and polarity. Anything polar or charged dissolves in H2O, whereas anything non polar or neutral cannot.