Part 2-Lesson 1

The Importance of water as a Solvent in Biological SystemsPart 2-Lesson 1ReviewThe GWB refers to the total distribution of water in all its forms and reservoirs on Earth. This distribution is uneven due to the following reasons:TopographyLatitudeClimate Earths systems are very complex and interconnected. A change to one system can impact others.Positive feedback amplifies a change to a system and cause it to increase in a snowball effect.Negative feedback cancels out changes in a system and promotes stable conditions.Water as a SolventWater is a simple chemical which make it crucial to all life. One of its important properties is its role as a solvent. A solvent (from the Latin solvere, "loosen") is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature. (http://en.wikipedia.org/wiki/Solvent)

Water as a solventThis property of water allows biological processes (diffusion) to occur rapidly in solutions.

For example, water carries nutrients and oxygen to calls where they are needed and transports carbon dioxide and other wastes away. All living things depend on this.

Water as a SolventWater is a good solvent because of its polarity. The water molecule forms an angle, with hydrogen atoms at the tips and oxygen at the vertex. Since oxygen has a higher electronegativity than hydrogen, the side of the molecule with the oxygen atom has a partial negative charge. (http://www.worldofmolecules.com/)Water as a SolventA molecule with such a charge difference is called a dipole. The charge differences cause water molecules to be attracted to each other (the relatively positive areas being attracted to the relatively negative areas) and to other polar molecules. This attraction is known as hydrogen bonding. (http://www.worldofmolecules.com/)

Water as a SolventWhen an ionic or polar compound enters water, it is surrounded by water molecules. The relatively small size of water molecules typically allows many water molecules to surround one molecule of solute. The partially negative dipoles of the water are attracted to positively charged components of the solute, and vice versa for the positive dipoles. (http://www.worldofmolecules.com/)

Water as a SolventIn general, ionic and polar substances such as acids, alcohols, and salts are easily soluble in water, and nonpolar substances such as fats and oils are not. Nonpolar molecules stay together in water because it is energetically more favourable for the water molecules to hydrogen bond to each other than to engage in van der Waals interactions with nonpolar molecules. (http://www.worldofmolecules.com/)

Water as a SolventAn example of an ionic solute is table salt; the sodium chloride, NaCl, separates into Na+ cations and Cl- anions, each being surrounded by water molecules. The ions are then easily transported away from their crystalline lattice into solution. (http://www.worldofmolecules.com/)

Water as a SolventWater as a solvent in biological systems is important because is allows for soluble substances to diffuse across a cell membrane. This allows cells to obtain essential nutrients and minerals and allows remove waste substances.

Relative solubility of Oxygen and Carbon Dioxide in WaterThe solubility of a gas in water varies with temperature. Both oxygen and carbon dioxide are soluble in water however water is capable of dissolving far more carbon dioxide than oxygen at any given temperature.

What might our planet be like if water did not have this ability to dissolve Carbon Dioxide?

Relative solubility of Oxygen and Carbon Dioxide in WaterThe Ability of water to dissolve both Carbon Dioxide and Oxygen decreases as the temperature of the water increases. The concentrations of Carbon Dioxide decreases more rapidly.

Solubility of oxygen and carbon dioxideOxygen and carbon dioxide are the two most vital gases for living things on Earth. The availability of these gases in an environment greatly affects the distribution and diversity of organisms that can live in that environment.

Solubility of oxygen and carbon dioxideAll organisms are classified as autotrophs (self feeders) or heterotrophs (other feeders). Autotrophs require carbon dioxide to make food by photosynthesis. All heterotrophs obtain their energy from the food chain, therefore they also depend on carbon dioxide.Solubility of oxygen and carbon dioxideMost of life on Earth respire aerobically: Oxygen is needed to for their cells to produce energy and carbon dioxide is produced as a waste product. Terrestrial organisms obtain the gases from the air. Aquatic organisms exchange oxygen and carbon dioxide through gills.

Solubility of oxygen and carbon dioxideTemperature is the most important factor affecting solubility of oxygen and carbon dioxide in water. The cooler the water the, the less the atoms vibrate resulting in larger spaces between the molecules. Its within these spaces which the gases are held. Because of this cold water can hold more dissolved oxygen and carbon dioxide than an equal volume of hot water.ActivityComplete DOT Points 2.1-2.2ReviewWater is a simple chemical which make it crucial to all life. One of its important properties is its role as a solvent. This property of water allows biological processes (diffusion) to occur rapidly in solutions. The solubility of a gas in water varies with temperature. Both oxygen and carbon dioxide are soluble in water however water is capable of dissolving far more carbon dioxide than oxygen at any given temperature. The Ability of water to dissolve both Carbon Dioxide and Oxygen decreases as the temperature of the water increases. The cooler the water the, the less the atoms vibrate resulting in larger spaces between the molecules.

HomeworkRead pages 90-95 Prelim Spotlight TextUpdate electronic vocabularyComplete DOT Point 2.1-2.2The Importance of water as a Solvent in Biological Systems

Part 2-Lesson 2Water SalinityThe majority of Earths water is in the oceans which are highly saline. This accounts for 97.3% of the water on Earth.

Water SalinityOf the remaining 2.7% which is classified as fresh, is in the form of ice, soil moisture, ground water and water vapour. This water that we classify as fresh is a scarce resource.

Water SalinityWe also must consider that the term fresh we use to describe some water does not mean pure. Because water is such a good solvent, water always contains dissolved minerals.

Water SalinitySome sources of fresh water contain so much dissolved minerals like salt that they are not suitable for drinking. Would you drink the river water? What minerals do you think it contains?

Water SalinityRivers like the Darling are classified as an inland river. These inland rivers of Australia are subject to periods of flood and drought. How do you think this affects the mineral contents of the water? Think about salt.

Water SalinityThe mineral content and salinity of Australias fresh water rivers vary considerably. Inland rivers naturally contain some salt washed into them from surrounding rocks and soil.

Water SalinityWhen the salt washed into the rivers is diluted by large volumes of water during floods, the salinity of the river is at its lowest. But after prolonged droughts, water levels drop and the ratio of salt to water rises.

Water SalinityThe first European explorers to reach the Darling River found it was to salty to drink! What do you think they would say today? What effects do you think this would have on the environment?

Water SalinityThe range of salinity native fish and aquatic plants can tolerate is unknown. Scientists have performed tests and taken samples of these organisms and know that species native to inland rivers are very salt-tolerant.

Water SalinityNative organisms survive unaffected when river salinity is at its highest. If fish from rivers with more consistent salinity levels were placed in saline water like this most would die.

ReviewThe majority of Earths water is in the oceans which are highly saline. This accounts for 97.3% of the water on EarthBecause water is such a good solvent, water always contains dissolved minerals.The mineral content and salinity of Australias fresh water rivers vary considerably.When the salt washed into the rivers is diluted by large volumes of water during floods, the salinity of the river is at its lowest. But after prolonged droughts, water levels drop and the ratio of salt to water rises.

HomeworkRead Page 92 Prelim Spotlight TextUpdate electronic vocabularyComplete DOT Point 2.3The Importance of water as a Solvent in Biological Systems

Part 2-Lesson 3ReviewThe majority of Earths water is in the oceans which are highly saline. This accounts for 97.3% of the water on EarthBecause water is such a good solvent, water always contains dissolved minerals.The mineral content and salinity of Australias fresh water rivers vary considerably.When the salt washed into the rivers is diluted by large volumes of water during floods, the salinity of the river is at its lowest. But after prolonged droughts, water levels drop and the ratio of salt to water rises.

Effects of Evaporation on SalinityComplete Practical pg 92 Prelim Spotlight TextThe Importance of water as a Solvent in Biological Systems

Part 2-Lesson 4EutrophicationThis is a process where nutrients become concentrated in waterways, causing an explosion in the population of surface dwelling algae (Algal Bloom).

EutrophicationThese blooms are a natural periodic process however human activities make them more serious, more frequent and more widespread than naturally. So what causes these algal blooms and what are their effects?

EutrophicationPlant growth is boosted by nutrients. When there are excess nutrients dissolved in waterways, plant populations can explode. Algae benefit the most because they live on or near the surface.

EutrophicationAs the algae population explodes it forms a green, blue-green, purple or red surface scum. This scum prevents most light from penetrating into the water cutting off light and killing bottom dwelling plants.

EutrophicationWithin a few days of the surface scum being established, decaying algae and vegetation use up most of the oxygen dissolved in the water and organisms living in the water suffocate and die.

EutrophicationThis algae generally remains in the waterway until rains replenish the system and flush away the surface scum.

EutrophicationIn NSW the type of algae bloom which is the worst problem is blue-green algae (cyanobacteria). This flourishes at times of low flow in inland waterways which are enriched by run-off carrying fertilisers.

EutrophicationBlue-green algae gives the water an unpleasant appearance and smell but also the cyanobacteria actively produce toxins that can kill humans and livestock that drink it. Bathing in this water can lead to rashes and skin problems. This presents a huge problem to rural communities that rely on such rivers to water their stock. How do you think it affects native animals?

ReviewEutrophication is a process where nutrients become concentrated in waterways, causing an explosion in the population of surface dwelling algae (Algal Bloom). These blooms are a natural periodic process however human activities make them more serious, more frequent and more widespread than naturally.Blooms block light from bottom dwelling plants and use up oxygen present in the water suffocating organismsBlue-green algae is toxic and can kill animals that drink the water

HomeworkRead Page 94 Prelim Spotlight TextUpdate electronic vocabularyComplete DOT Point 2.5Complete To Think About pg 95 Prelim Spotlight Text