Water

Water has a Unique Shape A negative charge on the Oxygen end Positive charge on the Hydrogen end You must know this model

Hydrogen Bonding Hydrogen Bonding is a inter-molecular attraction cause by different charges The H is attracted to the O because of the opposite charge

Solutions Solutions are a solute dissolved in a solvent In salt water; salt is the solute and water is the solvent Salt dissolves in water because water can separate the ions from each other The solute particles can not be filtered out of a solution

Solvation Solvation occurs when a solute dissolves Solvation is the process where molecules of the solvent surround the molecules of the solute http://www.youtube.com/watch?v=EBfGcTAJF4o

Kool-Aid Science What is the solute and the solvent in your Koo-Aid solution? Solute – the mix Solvent - the water How strong is your solution? Is it dilute or concentrated?

Concentration What does it mean when a solution is concentrated? It means that a lot of solute is dissolved in the solution

Dilute What does it mean when a solution is dilute? It means that there is not a lot of solute dissolved in the solvent

What the Problem? Concentrated and dilute are relative Think about coffee What is strong to one person is not strong to another These terms do not give a precise description of the solution We need a need new unit of measurement

Molarity Molarity is defined as Moles (that’s right moles again) divided by liters .5M means .5 moles per liter Molarity is the number of moles of solute dissolved in volume of solvent measured in liters Molarity can also be written in brackets [2.5] means 2.5 moles per liter The molarity is 2.5

Example What is the molarity of a solution that has 1 mole of salt dissolved in 500 ml of water First convert ml into liters 500 ml x 1L/1,000 ml = .5L Divide moles by liters 1mole/.5L = 2M

Another Example What is the molarity of a solution that has 31 grams of HNO3 in 250 ml of water. 31 x 1 mole/63 grams = .49 moles 250 ml x 1 liter/1,000 ml = .25 liters .49 moles/.25 liters = 1.96 M

What dissolves in What The rule is like dissolves in like, polar in polar and non-polar in non-polar Remember that water is polar, so a polar solid will dissolve in it. This is why non-polar oil will not dissolve in water.

Solubility SOLUBILITY is understood as a maximum amount of solute that dissolves in a solvent Miscible- The ability of a liquid to dissolve in another liquid Example water and vinegar, water and ethanol Immiscible – two liquids can not dissolve

Factors Affecting Solubility In general solids become more soluble at higher temperatures Think about making Jello In general gases become less soluble at higher temperatures but more soluble at higher pressure Why the rise in global temperature is adversely affecting the oceans

Factors Affecting Solubility Particle size In general, as particle size increases, solubility decreases Stirring Stirring increases solubility by increase contact of the solute and solvent particles If left alone sugar will dissolve, but stirring increase solubility

Degrees of Solubility You can pour as much solute as you want into a solvent, but only a set amount will dissolve Solubility is a physical property of a substance in given in grams of solute per 100 grams of solvent Ksp is the constant of solubility

Solubility Graphs Solubility graphs show the relationship between temperature and the amount of solute dissolved

Terms to know Saturated solution Unsaturated solution These solutions contain the maximum dissolved solute in the solvent Unsaturated solution These solution do not contain the maximum dissolved solute in solution – you can add more Supersaturated solution These solutions contain more than maximum due to heating of the solution – rock candy

Electrolytes Compounds that conduct electric current in solution Compounds that do not conduct a current are non-electrolytes A strong electrolytes have nearly all the solute exists as ions A weak electrolyte has only a fraction of the solute as ions

Suspensions and Colloids In a suspension the dissolved particles are large and will settle to the bottom Particles can be filtered out. Examples sand and water, salad dressing In a colloid the dissolved particles are intermediate size and exhibit the Tyndall effect In the Tyndall effect, light will both pass through the colloid and scatter Examples, milk, fog

Other Unique properties of water The density of water decreases at 0°C That is why ice floats The molecules of water in ice arrange themselves in a organized pattern The molecules in this pattern are more spread out than in the liquid state Ice takes up mores space than water at 2°C