Properties of Water

Earth has been called the “blue planet” From space, its surface appears to be mostly oceans of liquid water Water vapour is found in Earth’s atmosphere Frozen water occurs on mountaintops and at the North and South Poles The bodies of animals and plants consist mainly of water

Water is not only plentiful, it is also always on the move It moves in and out of our bodies It flows from ice cubes melting in a drinking glass It evaporates into the air from wet clothes or from oceans, lakes or rivers Evaporation explains why puddles disappears and streets dry out after a rain shower

Water also falls from clouds as different types of precipitation Examples: rain, snow The best way to understand the Earth’s water supply is to study it as a system Water constantly moves around between the sea, sky, land, and life

Water Cycle The water cycle is the process in which nearly all water on Earth moves continuously between the oceans, land, and atmosphere Liquid water is transformed into water vapour by evaporation, and water vapour is transformed into liquid water by condensation

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Water is truly a remarkable substance Water is truly a remarkable substance. It is the only substance that is found abundantly in all three states on the earth’s surface. Many of its unusual properties are produced by strong hydrogen bonds that cause water molecules to “stick” to each other and to “stick” to many other compounds. What most of us consider normal behaviour for water is most unusual for nearly all other substances.

Note: If a molecule of water were the size of a baseball; a drop of water would be the size of the earth! WOW! Other amazing properties: Water has an unusually high freezing point and boiling point for its molecular mass. Water is a liquid at room temperature, where similar compounds are gaseous. Water has the highest heat capacity of all substances. Water can absorb tremendous amounts of heat without raising its own temperature very much. In contrast, sand has a very low heat capacity.

Water is known as the universal solvent because it can dissolve large quantities of many different kinds of substances. Water has the highest surface tension of all liquids. Pure water has its maximum density at 4°C. Nearly all substances contract when they freeze; water expands 9% when it changes from water to ice.

Except for ammonia, water has the highest latent heat of fusion (melting or freezing). Water has the highest latent heat of evaporation. Water has a low viscosity (it flows easily). In contrast, cold molasses is very viscous. Water is very transparent for a liquid.

QUESTIONS If water froze like other liquids, how would this affect: skating on a pond? Plants and animals living in a lake during the summer? Glaciers are often called “river of ice” because compressed blocks of snow flows down the solid glacial ice. Why do glaciers flow?

Why is the temperature of the water near the bottom of a very deep, ice-covered lake as warm as 4˚C? Many small aquatic insects are able to walk on water. How? The temperature of inland regions fluctuates greatly from day to night, but the temperature stays about the same in coastal regions. Why?

On a very hot summer day, the sand at the beach feels very hot on your bare feet, while shallow pools feel much cooler. Why? Power outages in the winter often results in many homes having ruptured water pipes. Why?

Seawater contains almost every element or chemical found on earth. Why? Some major ocean surface currents can attain a speed of 5 knots (almost 10km/hr). In what ways do these major currents affect our lives on a daily basis?