Solubility of Solids, Solubility of Gases and Solution Concentration

T↑ S↑ Solubility of Solids Solubility is the maximum amount of a substance that will dissolve in a certain quantity of water at a specific temperature Solubility of solids is temperature dependent For solids: In other words, as the temperature goes up, so does the solubility. T↑ S↑

Solubility of Solids Factors that affect dissolving rate: Surface area of crystal Stirring/Agitation These only affect the rate at which a solute will dissolve, it does not influence the amount that will dissolve. Temperature affects both the rate and the amount that will dissolve Temperature affects different solutes differently

Solubility of Solids Types of Solutions Saturated – the maximum amount of a solute dissolved in a given amount of water at a certain temperature Unsaturated – less than the maximum amount of a solute dissolved at a certain temperature Supersaturated – more than the maximum amount of a solute dissolved at a certain temperature Occurs when a solution is heated, solute is added and then allowed to cool down ex: rock candy

Solubility Graph Any point on the line is saturated Any point above the line is supersaturated Any point below the line is unsaturated

Solubility Graph What amount of KNO3 will dissolve at 50°C? 80 grams •

Solubility Graph If 60 grams of KNO3 were dissolved at 80°C, what type of solution would be made? unsaturated •

Solubility Graph If 60 grams of KNO3 were dissolved at 30°C, what type of solution would be made? supersaturated •

Solubility Graph If 60 grams of KNO3 were put in a solution at 30°C, what type of solution would be made? saturated Think about putting sugar in cereal

Dissolving Ionic Compounds Dissolving is like a tug of war Solids will dissolve if strongly attracted to water molecules To dissolve, the attractive forces between ions must be overcome Dissolving occurs at the surface of the crystal 10

Dissolving Ionic Compounds The water molecule is attracted to the ions “Like dissolves Like” Polar will dissolve polar and ionic 11

Dissolving Ionic Compounds 12

T↑ S↓ Solubility of Gases The solubility of gases is quite different For gases: So, for gases, as the temperature goes up, the solubility goes down Think about an opened pop or one that gets warmer T↑ S↓ 13

Solubility of Gases Please notice that the solubility of gases is far less soluble in water than solids

Solubility of Gases The solubility of gases is directly proportional to the gas pressure on the liquid If the pressure doubles, the amount of gas dissolved would double Open up a pop – what happens? The pop will “go flat” even though there is still CO2 in the pop The pressure of CO2 in the pop will try to equal the atmospheric pressure of CO2

Solution Concentration Solution Concentration is the quantity of solute dissolved in a quantity of solution (solute + solvent) What is the concentration of a solution made from 20 g of sugar in 80 g of water? g of solute × 100 g of solution 20 g sugar × 100 = 20% 100 g solution

Solution Concentration Some common concentration units: pph – parts per hundred (also referred to as percent) ppt – parts per thousand ppm – parts per million ppb – parts per billion

Solution Concentration A 5% (pph) salt solution is how many ppm? Cross multiply and divide : 5 × 1000000 ÷ 100 and you should get an answer of 50,000 ppm 5 X = 100 1000000

Oxygen – Supply and Demand All animals need oxygen gas (O2) to survive Aquatic organisms need a continuous supply of dissolved oxygen (DO) Ways that oxygen gets into water Dissolved directly from the air above the water Aeration Photosynthesis

Aeration Aeration – air is forced into water by a dam, by rapids in a river or stream or by the waves on a beach

Photosynthesis Photosynthesis – the production of oxygen by green plants through a chemical reaction Energy(sun) + 6 CO2 + 6 H2O → C6H12O6 + 6 O2

Oxygen – Supply and Demand Aerobic Bacteria, oxygen consuming bacteria, also need oxygen to survive Live off of biodegradable substances which they break down More biodegradable substances = more aerobic bacteria More aerobic bacteria = greater struggle for fish

Oxygen – Supply and Demand Most fish require a minimum of 4 ppm (0.004 g/1L) of DO Less than that and fish will either migrate or die

Bibliography http://www.whfreeman.com/Chemcom/ http://grapevine.net.au/~grunwald/une/KLAs/science/irrigation-photosynthesis.gif