Chapter 16 – Solutions Mr.Yeung

Objectives Solutions –Types How some solutions mix and some don’t Polarity Electronegativity

Solutions What are solutions? –What is in a solution? Solute and solvent Solute – dissolved particles in a solution. Ex: sugar Solvent – dissolving medium in a solution Ex: Water –What if you are mixing two liquids? Which one is the solute? Solvent? Dominant one becomes solvent

Types of solutions How many types of solutions do you think we have?

9 types of solutions Solid in solid –Ex: copper in silver, coins (penny) Solid in liquid –Ex: Salt in water, sugar water Solid in gas –Ex: Microscopic particulates in air Gas in Solid –Marshmellow Gas in Liquid –CO2 in drinks (Coke), Oxygen in water Gas in Gas –Oxygen in air Liquid in gas –Water vapour in air Liquid in solid –Cheese, jelly Liquid in liquid –Alcohol in alcoholic drinks –Methanol in water (gas line antifreeze)

So what happens if you mix oil and water? How come they do not mix? They do not mix due to polarity. What is polarity? –Where else have you heard of the term ‘polar’?

Polar molecules A polar molecule is one that has their electrons unevenly distributed. The molecule may have more electrons on one side of the molecule. –Other polar molecules – NH3, SO2, H2S

Non-polar molecules A non-polar molecule is one that the electrons are distributed more symmetrically and thus does not have an abundance of charges at the opposite sides. The charges all cancel out each other. Ex. H2, C2H4, CH4, O2,

Polarity of water Water is a polar molecule There is an uneven distribution of electron density Partial negative charge near the oxygen and positive near the hydrogen atoms Polarity allows salt to dissolve in water

Polarity in solutions Liquid in a liquid –Ex. Both alcohol and water are polar molecules, therefore they mix with each other Gas in a liquid –Ammonia is polar gas and water is polar. They mix to form a solution Gas in a gas –The major gases in air, Nitrogen (N2), Oxygen (O2) and Carbon Dioxide (CO2) are non-polar molecules and thus will combine to form a solution. –Air is a solution where molecules are evenly spread throughout.

Rules for mixing solutions Polar molecules form solutions with other polar molecules Non-polar molecules form solutions with other non-polar molecules Water is a polar molecule and oil is a non- polar molecule. Thus they won't form a solution. On the other hand, since alcohol is a polar molecule, it will form a solution with water.

–Electronegativity is the tendency of an atom to attract electrons to itself. –Metals tend to lose electrons and non metals tend to gain electrons –As we move from left to right, electronegativity increases because the outer electron shell is closer to be filled –Bigger atoms have lower electronegativity cause they are bigger, more ‘outer shells’ in the atom What is Electronegativity?

Electronegativity Can predict the types of bonds involved –Covalent –Ionic Know the trends of electronegativity!

Journal questions What happens when you mix oil and water? Why? Explain in your own words in a ‘chemistry’ sense. Generate your own examples for the following –Solid in liquid –Solid in solid –Solid in gas –Liquid in solid –Gas in liquid –Gas in gas Comments/Questions: