2.1 The Role of Water in the Cycles of Matter (pages 34 – 40)

Water is: an excellent carrier of dissolved minerals and other materials. an effective medium for transferring energy. a universal solvent.

Water has: has a lower density when it is a solid a relatively high boiling point and melting point. special adhesive and cohesive properties. a high heat capacity.

Water is an excellent carrier of dissolved minerals and other materials: As water moves from place to place it carries a variety of other substances. for example: water in the soil may contain nitrogen and phosphorus or toxins like methylmercury.

Water is an effective medium for transferring energy: Water vapour that rises at the equator rises and moves towards the poles, releasing heat as it expands and cools. Liquid water transfers heat in ocean currents from warm regions to cooler regions. The warm air over the water can moderate the temperature over nearby land.

Water is a universal solvent: A water molecule consists of two hydrogen atoms that are covalently bonded to one oxygen atom. the hydrogen end of the molecule has a slightly positive charge and the oxygen end has a slightly negative charge, making water a polar molecule. This polarity allows a water molecule to form hydrogen bonds between the hydrogen of one molecule and the oxygen of a nearby molecule.

Water has a lower density when it is a solid: Ice floats on top of liquid water because it is less dense. When water cools, molecules of water slow down and allow for all of the possible hydrogen bonds to form; individual molecules are held at equal distances from each other resulting in a lower density.

Water has a high boiling and melting point: Hydrogen bonding explains why water remains liquid over a large temperature range. An individual hydrogen is weak; hydrogen bonds break and re-form frequently. Many hydrogen bonds together are strong; require a large amount of energy to break them.

Water will only change phase from a liquid to a solid (boil) when the many hydrogen bonds are broken; therefore, water has a high boiling point. Water will only change phases from a solid to a liquid (melt) when the many hydrogen bonds are broken; therefore, water has a high melting point.

Water has special adhesive and cohesive properties Hydrogen bonding causes cohesion, the attraction of water molecules to each other. Cohesion is responsible for surface tension, the reason many insects can walk on water.

Adhesion is the attraction of water molecules to the molecules of other substances. Adhesion is responsible for water sticking to the sides of a test tube or a tree’s xylem vessels – allowing water to move against the pull of gravity.

Water has a high specific heat capacity Heat capacity is the amount of heat a substance can absorb or release for a given change in temperature. Water requires a large amount of energy to affect a small amount of change in temperature. Water takes a long time to heat and cool. Bodies of water such as oceans and lakes have a moderating effect on the air temperatures of nearby land.

Today’s Surface Temperatures

Answer the questions Question 1. Water is a polar molecule, what does this mean? Question 2. How does water’s polarity affect the process of transpiration?

The Hydrological Cycle Biogeochemical Cycle: the cyclical route that water or other chemical nutrients take through the biotic and abiotic components of the biosphere.

The hydrologic cycle is a cycle of evaporation and condensation that determines the circulation of water through the atmosphere and biosphere. The Water Cycle

As water travels through the biotic and abiotic components of the biosphere, it carries much material with it, including chemical nutrients. This links the hydrologic cycle with the biogeochemical cycles, through which nutrients travel.

Societal Uses of Water Alberta has rich supplies of fresh water from rivers, lakes, wetlands, and undergrounds sources. Population growth and increases agricultural and industrial uses has increased the demand for water in the province and on a global scale. Water that cannot be cleaned of toxic chemicals and pathogens in no longer useful. If it is released into the environment, it can cause great harm to the ecosystem.

Question 3. Based on the pie chart of water use in Alberta, which sector of water use should be decreased? Justify your response.

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