Do Now & Announcements Tear off HW and hand it in Answer the questions based on the vapor pressure graph Friday: Lab & Review Monday 3/23: Unit 8 Test

Label the following diagram indicating vapor pressure (VP) and air pressure (AP):

By putting ice on top of the flask Temp of air inside flask: Pressure of air inside flask: **Explain, in terms of temperature change, atmospheric pressure, and vapor pressure, what happened in the demonstration

Polarity Polar Molecules- Nonpolar Molecules non-symmetric, unequal distribution of charge in a molecule Water is considered a polar solvent Polar molecules can form attractive forces with water molecules Nonpolar Molecules symmetric distribution of charge in a molecule

Polarity and Solubility Demo “Like Dissolves Like”

Polarity and Solubility: “Like dissolves like” Polar substances do not dissolve in nonpolar substances Ex: water and oil Polar substances dissolve in polar solvents Ex: water and alcohol Nonpolar substances are dissolve in nonpolar substances Ex: oil and soap

Covalent (Molecular) Compounds Properties of Solids Ionic Compounds Covalent (Molecular) Compounds Metals Made up of…   Electrons are…. Physical Properties: ________ melting point & boiling point Solids ______________ conduct electricity When dissolved in water: _______ conduct electricity Solids _____________ conduct electricity When dissolved in water: _____ conduct electricity _______ melting point & boiling point Solids _____ conduct electricity

Ionic Compounds Metal + Nonmetal Electrons are transferred HIGH melting point & HIGH boiling point Solids DO NOT conduct electricity Ionic compounds dissolved in water DO conduct electricity (electrolytes)

Covalent Compounds 2 or more Nonmetals Electrons are shared LOW melting point & LOW boiling point Solids DO NOT conduct electricity Covalent compounds dissolved in water DO NOT conduct electricity (nonelectrolytes)

Metals Made up several atoms of the same metal Electrons are constantly moving HIGH melting point and HIGH boiling point Solids DO conduct electricity

Note Metals are found to the left of the “staircase” on the periodic table Nonmetals are found to the right of the “staircase” on the periodic table

Definitions Kinetic Energy=the energy associated with moving particles (i.e. atoms) Temperature=measure of the average kinetic energy of a sample of a substance. Heat=is measured as the energy that is transferred from one object to another because of a difference in temperature. The direction of heat flow is always from the hotter object to the colder object.

Demo

Specific Heat Capacity: The amount of energy needed to raise the temperature of 1 gram of a substance by 1°C Heat = Energy transferred due to a difference in temperatures. The amount of heat absorbed or released in a physical or chemical reaction can be calculated using the equation q = mCΔT

Example How much heat is required to raise the temperature of 5 grams of water from 20°C to 100°C? The specific heat of water is 4.18 J/g°C.

Answer “practice 1” and “practice 2” questions

Answer questions 1-7 based on the “Heating Curve”

1. During which 3 line segments does the temperature of the substance increase? 2. During which 2 line segments does the temperature of the substance remain the same?   3. At which point do the molecules of the substance have the lowest average kinetic energy? The highest?   AB, CD, and EF BC and DE Lowest average KE: A Highest average KE: F

4. Which phases of matter are present during segment BC?   5. Which phases of matter are present during segment DE? 6. Even though heat is being added to the substance the entire time, why do you think there is no change in temperature during segments BC and DE? Where do you think the heat energy is going or being used for?    7. Comparing segments B–C and D–E, what information is conveyed by the observation that segment D–E is longer? Solid and liquid Liquid and gas The heat is being used to melt the substance (BC) or boil it (DE) It takes more heat energy to boil the substance than it does to melt it

Kinetic vs. Potential Energy Kinetic Energy=the energy associated with moving particles; related to temperature. Potential Energy=the energy associated with the spaces between the atoms It is NOT related to temperature; it is related with phase change

*Heat energy is being transferred to either KE or PE *When KE is changing, PE remains constant *When PE is changing, KE remains constant ↑ ↑ None (molecules still pretty close together) None None ↑ (Molecules are getting further apart as solid changes into liquid) None ↑ ↑ (molecules still loosely together) None None ↑ (Molecules are getting further apart as liquid changes into gas) ↑ ↑ None (molecules still far apart)

gas condensation liquid freezing solid We can also apply the same concepts to a cooling curve, in which a substance is cooled (or heat is removed from a substance) over time. ↓ ↓ None (molecules still far apart) None None ↓ (Molecules are getting closer together as gas changes into liquid) ↓ ↓ None (molecules still loosely together) ↓ (Molecules are getting closer together as liquid changes into solid) None None ↓ ↓ None (molecules still pretty close together)