Catalyst End

Supersaturated sodium acetate tower

Lecture 4.9 – Solution Chemistry Loose Ends

Today’s Learning Targets LT 4.10 – I can compare and contrast the three types of intermolecular forces (Van der Waals, dispersion, and hydrogen bonding), identify the types in a given solution, and analyze chemical properties that result because of these forces. LT. 4.11 – I can express the concentration of a solution in terms of mass percentage, mole fraction, molarity, and molality.

Solute + Solvent  Solution Solution Saturation Solute + Solvent  Solution Based on the amount of solute in the solution, we can characterize a solutions saturation Saturated – A solution in equilibrium with solute. No more solute may be added. Unsaturated – Less solute than is needed to achieve saturation is contained in the solution. Supersaturated – The solution contains more solute than can be dissolved.

The Dissolving Process The dissolving process is facilitated by motion of liquid molecules and intermolecular forces. Liquid molecules are moving in random motion. When a molecule is dissolved in water, water molecules hydrogen bond with one another to form a cage to dissolve.

How does salt dissolve water? clip

Dissolving We can alter the rate at which the solute dissolves by: 1. Changing the temperature 2. Changing the surface area of the solute 3. Changing the pressure of the solution.

Temperature and Dissolving As you increase the temperature, molecules start moving faster. By moving faster, the molecules are better able to grab the solute, form the cages around them and pull them into the solution. Therefore, the faster molecules are moving, the faster something dissolves.

Temperature and Dissolving Rate Cold liquid Hot liquid

Surface Area and Dissolving As you increase the surface area, the rate at which the solute dissolves increases. As you increase the surface area of a substance, you are providing more sites for the solvent to interact with the solute.

Surface Area and Dissolving

Pressure and Dissolving As you increase the pressure, the rate at which the solute dissolves increases. The solubility and pressure relationship is clearly seen when a gas dissolves in a liquid. When a gas is above a liquid and the pressure is increased, the gas molecules collide more often with the wall of the liquid and this causes more gas to be pushed into the liquid.

Review Time Rate yourself on the LTs 4.1 – 4.12 Identify the areas that require the most practice and begin working on those stations first: Station 1 – Station 2 – Station 3 – Station 4 – Station 5 – Station 6 – Station 7 – Station 8 – Station 9 –

Closing Time Test this Thursday/Friday Stations uploaded to the website. You will have the first hour to review before the exam. NOTE – this is not enough time to review everything that you need to. Review packet contains extensive amount of problems.