Catalyst

1. Describe how dispersion forces are created2. What intermolecular forces does HF contain?3. What intermolecular forces does NCl3

contain?

End

When is the last time you helped

someone?

Every day is a collaborative day!

Does it Dissolve?

Justify – TPS• Why do some things dissolve in water, but

other things do not?

Lecture 4.3 – The Dissolving Process and the Rate of Dissolving

Today’s Learning Targets• LT 4.1 – I can discuss how ionic solids dissolve due to the

random molecular motion of the water molecules. • LT 4.3 – I can compare and contrast various intermolecular

forces and relate them to the dissolving process of a solid. • LT 4.4 – I can hypothesize how surface area, temperature,

and pressure impact the dissolving process of a solid.

Why do substances dissolve?

I. 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.

II. Like Dissolves Like

• Like substances dissolve like substances • If something has a charge, then it will not be

able to dissolve something that does not have a charge.

Summarize

Sugar Cube Investigation• We can make statements

about what we think is the answer to a question, but a good scientist experiments

• You are going to be doing an investigation with your group to determine how surface area and temperature impact the rate at which something dissolves.

Lab Conduct• Follow the procedure that has been given to

you• Respect the equipment. It costs a lot of money

to replace this stuff• Use the chemicals in a responsible and safe

way• Clean up the space when you are done• Read the steps, they will tell you what to do.

Lab Work Time

Lab Debrief• What happens to the rate at which the sugar

dissolved as you increased the temperature?• What happens to the rate at which the sugar

dissolved as you increased the surface area?• Why?!?!?!

A Problem

Cools down to room

temperature

Gross!

Justify – TPS• Why does this solid appear at cold

temperatures, but it wasnt present when the cider was hot?

How does temperature, pressure, and surface area impact rate of dissolving?

I. Dissolving• We can alter the rate at which the solute

dissolves by:1. Changing the temperature2. Changing the surface area of the

solute3. Changing the pressure of the solution.

II. 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.

Remember What Dissolving Looks Like?

Temperature and Dissolving Rate

Cold liquid Hot liquid

III. 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

Making a Carbonated Beverage

Justify – TPS

• Why does your soda become carbonated when you open it? What is happening?

IV. 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. • Gases can dissolve into liquids.

IV. Pressure and Dissolving• 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.

Summarize

Mind Maps• We will be making mind maps

to understand the connections between concentration calculations and solution chemistry

• In the center of our mind map will be the term “Solution Chemistry”

• You will have branches coming up for all the terms that you think are important for the idea of solution chemistry

Mind Map Work Time• Your mind map must contain the following words/terms/Ideas:

– Molarity - Hydrogen Bonding– Percent Composition - Dipole-Dipole Forces– Crystal Lattice - Dispersion Forces– Intermolecular Forces - How atoms are – Solvent arranged in solids/– Solute liquids/gases– How dissolving occurs -How pressure, volume at the

molecular level and temperature influence dissolving

• Put as many things as you know! USE NOTES!• Use colors!

Closing TimeClosing Time• Lab Report Methods/Results due Tuesday!