Properties of Water Unit 2

I. Water Is A SolventA. Solvent – substance doing the

dissolving

B. Solute – substance being dissolved

C. Major difference in freshwater and sea water is presence of salt (NaCl)

II. Structure of Water

A. Pure H2O – two hydrogen

and one oxygen.

B. Salt Water – Six elements

and compounds comprise about 99% of sea

salts.

III. pH of Water

A. H2O can separate into H+ and OH- ions.

B. The presence of these ions cause water to become acidic or basic.

C. pH of pure water – 7

“neutral”

IV. Dissolved Oxygen in Water

A. Oxygen is found in water even though it does not dissolved easily.

B. Dissolved oxygen is measured in parts per million (ppm).

C. Ocean water can hold from 1 to 12 ppm depending on the temperature of the water.

(oxygen in air is 200 ppm)

V. Sea Water

A. Ocean water is made up of about 96.5 percent water molecules and 3.5 percent NaCl (table salt).

B. Calcium Carbonate is also a common compound found is the seas.

A. Oceanic waters typically have 35g of salt dissolved in 1000g of water (3.5%).

B. Salts accumulate in the oceans as rain leach sediments from the land.

VI. Salinity

VII. Temperature

A. Ocean water temperatures vary between -2 to 30°C.

B. Temperatures below 0ºC arepossible because salt

water freezes at colder temperatures than pure water.

VIII. Pressure

A. Organisms on land experience atmospheric pressure.

B. Marine organisms experience water pressure and

atmospheric pressure.

C. Units of Pressure

1. Atmospheric pressure: atm

2. With each 10m (33ft) of increased depth, another atmosphere of pressure is added.

0m 10m

20m 30m

40m 50m

60m 70m

80m 90m

1atm 2 3 4 5 6 7 8 9

10atm

IX. Buoyancy -

an upward force exerted

by a fluid an object is in.

X. Density

A. Mass of a substance per unit of volume.

B. Formula: D= m/v

C. Unit: g/ml or g/cm3 (ml = cm3)

D. Density of Pure H2O = 1 g/ml

(impurities in water cause the density to increase)

E. Principle of Density

1. Objects of greater density than the fluid they are in – will sink in the fluid.

2. Objects of lesser density than the fluid they are in – will float in the fluid.