Properties of water

1.

–-

Composed of 2 hydrogen and 1 oxygen atom bound extremely tight–covalent bonding

Oxygen- 8 electrons

Hydrogen- 1 electron

+

2. Polar molecule; partially negative charge develops on one side, partially positive on the other.

Promotes “hydrogen bonding”

· Each water molecule attracted to 4 adjacent molecules (cohesion)

· Adhesion, water molecules “stick” to other materials (eg, meniscus)

· Capillary rise

· Surface tension (round water drops)

3. Latent heat- requires much energy to change state; eg, to evaporate water (liquidà vapor) ~600 cal/gram

4. Specific heat≡ heat required to raise 1g of a substance 1°C.

(for water, » 1 cal/g/°C)

5. Density- for most substances, as they cool they contract and become denser, & solids more dense than liquids of same composition. For water, maximum density as 39°F (4°C)

6. Water, the “universal solvent”

· Some compounds, especially salts, can be disassociated by water

“Hydration” spheres surround Na⁺ & Cl^-, 6 H₂O’s each

-NaCl would be an example of “solute”

-NaCl dissolved in solvent water produce “solution”

-Water can be prolific solvent: 70 lbs of ammonium nitrate fertilizer in 1-gallon water!!

· Some polar compounds are dissolved by water (carbohydrates, proteins) but do not disassociate

· Some non-polar substances can be dissolved (gases such as O₂, CO₂, N₂)

-Increasing temperature generally promotes dissolution of salts and polar compounds.

-Increasing temperature reduces the dissolution of non-polar gases.

The dissolving capabilities of water are profound:

The water will even very slowly dissolve the glass that holds the water.

Human food dissolved in order for it to be distributed throughout the body.

Plant nutrients typically dissolved in water before taken up by roots.