WELCOME BACK u Pick up a Solutions Packet Open to the notes page & copy down the essential question EQ: How can solutions be classified? How do you read a solubility graph? u Turn in LATE Gas Packets u If you were absent for the Gas test you will be making it up IN CLASS TODAY

Intermolecular Forces u Hydrogen Bonding H bonded to N, O, F u Dipole – Dipole Polar: opposite charged ends –Polar ionic/Polar Covalent u London Dispersion Forces Unequal distribution of electrons around the nucleus.

Solutions

Recap….types of matter

Elements & Compounds are pure substances… Elements are substances that are composed of only one kind of atom. Elements cannot be broken down by chemical change. A compound is a pure substance made of different elements, chemically bonded together. ALWAYS in the same proportions.

Mixtures are NOT pure substances; their composition can vary. Mixture of elements, elements and compounds, or compounds! In each example above, there’s more than one thing there!

Back to the big picture… Note: A pure substance can be represented by a chemical formula Examples: Fe, H 2, NaCl, CO 2

Types of Mixtures u Heterogeneous Mixtures Mixture that does not have the same properties throughout the mixture. “Hetero” = different Individual substances remain distinct u Homogeneous Mixture Solutions Mixture with the same properties throughout. “Homo” = same

Solutions occur in all phases u Solid solution: steel An alloy is a solution where two or more solids are combined. A homogeneous mixture of metals u Gas solution: air u Liquid solutions: most common in chemistry, recognized by the symbol (aq)

Solution Vocabulary u The solvent does the dissolving: whatever you have more of. Water is the universal solvent u The solute is dissolved; it’s the thing you have less of. u Memory trick: “solvent” has more letters than “solute,” so it’s the thing you have more of. u Example Salt(solute) + Water(solvent) = Salt Water

Solutions homogenous mixture ~ Mixture: parts are not chemically combined ~ each component of the solution keeps its identity ~ Will NOT settle out solutesolvent composed of solute and solvent gets dissolved does the dissolving

Why does anything dissolve? Why doesn’t it just sit there? Solubility guideline: “Like dissolves like.” Polar solvents (Ex. water) dissolve polar things. Opposite ends. Non-polar solvents (Ex. oil) dissolve non-polar things. Same ends.

How does soap work? u Soap has a long non-polar “tail” and a polar “head” A drop of bacon grease in water Grease is non-polar Water is polar Soap lets you dissolve the non-polar in the polar.

Soap molecules tie the grease to the water, so when you rinse away the water, the grease goes along with it!.

Electrolytes u An electrolyte is a substance that, when dissolved in a solvent or melted, conducts an electrical current. Species such as HCl that completely ionize in water are called strong electrolytes Compounds that only partially ionize in water are called weak electrolytes. u A nonelectrolyte does not conduct a current when dissolved. Compounds that do NOT ionize in water.

Solubility u Solubility: the amount of a solute that will dissolve in a given solvent What factors affect solubility? –AMOUNT Temperature Pressure –RATE Particle Size: smaller increase rate of dissolving –More solute/solvent contact Stirring

Dissolving Gases u You can increase solubility, dissolve more, of a gas in a colder solvent. u Pressure affects the solubility (amount) of a gas that can dissolve in a liquid.

u If you increase the pressure, think of pressing the gas particles into the liquid. u Increasing pressure always increases the amount of gas that can be dissolved in a liquid.

Dissolving Solids u Higher temperature usually increases the solubility (amount) of a solid dissolved in a liquid. But not always! u We must read the effect of temperature from a graph of experimental data.

Which substance is most soluble at 40°C? How many grams of NH 4 Cl will dissolve at 50°C? What two substances have the same solubility at 24°C? How many grams of NaNO 3 will dissolve in 300.0g of water at 10.0°C? NaNO 3 ~ 50 grams KNO 3 and Yb 2 (SO 4 ) 3 ~ 240 grams (80 x 3)

Homework: Solutions WS and Solubility Graph Practice

Basic Concepts Phase: –A homogeneous region with distinct structure and physical properties –In principle, can be isolated –Can be solid, liquid or gas Phase Diagram –Representation of phases present under a set of conditions (P, T, V)

Concepts….. Phase transformation –Change from one phase to another –EX. L S, S G etc. –Occurs because energy change is negative/goes from high to low energy state Phase boundary –Boundary between phases in a phase diagram

Phase Diagrams A phase diagram shows the conditions at which the distinct phases of matter can occur at equilibrium.

Phase Diagram Vaporization CondensationSublimation Deposition Melting Freezing

Phase Diagram Critical Point:

Phase Diagrams Triple Point The triple point of a substance is the temperature and pressure at which gas, liquid, and solid coexist in thermodynamic equilibrium. Gas Liquid Solid

Phase Diagrams Triple Point For water, the combination of pressure and temperature are exactly °C and atm. At that point, the liquid can boil and freeze at the same time. Gas Liquid Solid

Phase Diagram According to the red line on the phase diagram, if we apply enough pressure to ice, it will melt into liquid water. What are the practical applications?

Normal Pressure occurs at 1 atm Solid Liquid Gas

What is the normal melting point of this substance? What is the normal vaporization point of this substance? Solid Liquid Gas