Chemistry CHAPTERS 11-12

Know the direction of heat flow (11)

• Heat always flows from the object of higher temperature to the object with lower temperature, until they reach thermal equilibrium (same temperature).

Know the main statements of the kinetic theory of matter (11)

1. All matter is made of incredibly small particles (atoms, molecules, and ions) and these particles have mass.

2. These particles experience constant random motion.

3. When particles collide, the collisions are perfectly elastic.

4. The energy of the particles is directly related to its temperature. The particle's actual motion will depend on its energy and its mass.

Determine the difference between a system and its surroundings (11)

1. A system is anything you wish to study, and the surroundings are everything else.

2. If you want to study Earth, and how it moves through space. The Earth would be the system, and the rest of the universe is the surroundings.

3. If you want to study the forces acting on a water molecule in a solution. The water molecule would be the system, and the surroundings would be the rest of the solution, the container it is in, the table it sits on, the air around it, etc.

Define temperature and heat (11)

1. Temperature - The average kinetic energy of a system (Kinetic energy = energy in motion.)

2. Heat - The flow of energy between two substances due to their initial difference in temperature.

Describe heat flow based on the idea that heat lost = heat gained (11)

1. If you have a cold ice cube in your hand, the heat FROM your hand transfers to the ice cube. Your hand loses heat energy to the ice cube and your brain interprets this loss of energy as feeling cold.

2. If your hand touches a hot cup of coffee in a thin china cup, the heat from the hot coffee will flow to your hand, thus signaling your brain that the cup is hot.

Describe how a liquid thermometer works (11)

• A liquid thermometer measures on thermal expansion. When in hot liquid, heat is transferred to the liquid inside the thermometer. When in cold liquid, heat flows out of the liquid.

List and describe 4 different types of thermometers (11)

• Alcohol, mercury, bimetallic strip (oven thermometer), and digital.

Know the pros and cons of a mercury alcohol thermometer (11)

1. Alcohol thermometer: Safe, but not exactly accurate in its reading.

2. Mercury thermometer: Toxic/dangerous if shattered, but has an accurate reading.

Name three temperature scales and states what the scales are based on (11)

• Fahrenheit, Celsius, and kelvin.

Define absolute zero (11)

1. 0 in Kelvin, -273.15 in celsius, and -459 in fahrenheit. 

2. Absolute zero is when particles have no thermal energy left to give. Matter disappears and particle motions stop moving.

3. All molecular motion stops = zero kinetic energy of particles.

Define specific heat (11)

1. It refers to the amount of energy a substance has to transfer to change its temperature.

2. It is the amount of energy required to raise the temperature of a unit mass of that substance (usually 1 gram) by 1 CELSIUS or 1 KELVIN.

Describe the difference between an exothermic and endothermic reactions in terms of direction of heat flow, how it feels, and.. (the triangle next to an H.) (11)

1. Exothermic - Heat is given off from a system to the surroundings in this type of reaction. (Exo means out) This reaction feels WARM. The change in heat energy is released by the system, is negative, and loses heat energy (gets cooler).

2. Endothermic - Heat is absorbed in this reaction. This reaction feels COLD. The change in heat energy is absorbed, positive, and gains heat energy (gets warmer).

Define an activation energy (11)

• It is the MINIMUM additional amount of energy that must be absorbed before a reaction may begin.

Describe the heat energy flow that occurs when you put a room temperature metal spoon into a pot of boiling water (11)

• It is ENDOTHERMIC because heat is flowing FROM the boiling water INTO the metal spoon. Heat always moves away from high temperature to low temperature until both are equal equilibrium (same temperature).

How is the digital thermometer different from a bimetallic strip thermometer? When would each be used? (11)

1. A digital thermometer uses electronic sensors to detect temperature and later convert to a digital reading, while a bimetallic strip thermometer uses two different metals bonded together that will expand at different rates when heated. Eventually causing the metal to bend.

2. Digital - Body temperature, medical, and cooking.

3. Bimetallic - Ovens, thermostats, and industrial equipment.

What is the Kelvin scale based on? Fully describe this point. (11)

• It is based on absolute zero/-273.25 Celsius, lowest temperature possible in space, and to the point where all motion stops. Meaning no kinetic energy.

What is the difference between conductivity and specific heat? (11)

1. Conductivity - the ability for heat energy to flow through a substance.

2. Specific heat - the amount of energy required to raise the temperature of a unit mass of a substance by 1 Celsius or 1 kelvin.

A metal has a low specific heat. Water has a high specific heat. What does this mean? (11)

1. Metal heats up quicker with LITTLE heat energy and cools down quicker too.

2. Water takes a lot of energy to change its temperature, heat up, and retains heat longer.

3. Low specific heat = heats/cools fast.

4. High specific heat = heat/cools slow.

In what type of reaction is heat energy absorbed to make the reaction proceed? (11)

Endothermic.

In what type of reaction is heat energy written on the left of the equation? (11)

Endothermic.

In what type of reaction is heat energy written on the right of the equation? (11)

Exothermic.

Bond breaking (requires or releases) heat energy. (11)

Requires.

Which type of reaction feels warm? (11)

Exothermic.

Bond formation (requires or releases) heat energy. (11)

Releases.

What type of reaction feels cold? (11)

Endothermic.

In what type of reaction do the products contain less heat energy than the reactants? (11)

Exothermic.

In what type of reaction is the (triangle-H) sign positive? (11)

Endothermic.

In what type of reaction is heat energy released to the environment? (11)

Exothermic.

In what type of reaction do the products contain more heat energy than the reactants? (11)

Endothermic.

In what type of reaction is the (triangle-H) sign negative? (11)

Exothermic.

State the difference between an intramolecular and intermolecular forces (12)

1. INTRAmolecular - Any force that holds together the atoms WITHIN a molecular, metal, or ionic compound. (STRONG)

2. INTERmolecular - Weaker forces of attraction which are present BETWEEN neighboring molecules or atoms that are not actually bonded. (WEAK)

Describe the 3 types of intramolecular forces and determine which type a given substance has (12)

1. Covalent: A nonmetal that is solid, like C or Si

2. Metallic: A metal like aluminum or an alloy (a mixture of metals) like brass

3. Ionic: An ionic compound (made of a metal and a nonmetal) like NaCl

4. REVIEW THIS

Describe 3 types of intermolecular forces discussed in your notes and determine which type occurs between representative particles of a given substance (12)

1. Hydrogen Bonding: If polar and meets criteria. (Criteria: The attraction between a hydrogen atom covalently bonded to either a nitrogen, oxygen, or fluorine atom in one molecule to a lone pair or electrons of a nitrogen, oxygen, or fluorine atom in a neighboring molecule).

2. Dipole - Dipole Forces: The attractive force between the positive and negative end of two dipoles (polar molecules).

3. London Dispersion Force: The attractive force between a temporary dipole and an induced dipole. This can occur between nonpolar molecules or atoms that are not bonded with an intramolecular force.

4. STRONGEST to WEAKEST: Hydrogen, Dipole, and London.

Determine relative states of matter and relative melting points/boiling points based on strongest type of intramolecular/intermolecular force present (12)

1. Because ionic bonds, covalent bonds, and metallic bonds tend to be stronger than intermolecular forces, substances held together by thesis types of bonds tend to be solids at room temperature and have fairly high melting points and boiling points. (INTRAMOLECULAR)

2. Substances held by weaker intermolecular forces tend to be liquids and gases at room temperature. (INTERMOLECULAR)

   1. Water/liquid - Hydrogen bonds, melting point 0 Celsius.

   2. HCl/gas - Dipole-dipole forces, melting point -114.2 Celsius. 

   3. Helium/gas - London dispersion forces, melting point -272 Celsius.

State and explain the difference between solids, liquids, and gases for the following areas: location, intermolecular forces, density, compressibility, shape, volume, type of energy, diffusion, and expansion when heated (12)

1. Solids - Packed tightly and orderly/very close, VERY strong forces, VERY HIGH density, A LITTLE compressibility, DEFINITE/FIXED shape, NO shape + volume, vibrational energy, VERY LITTLE diffusion, and A LITTLE expansion when heated.

2. Liquids - Slip and slide/no fixed positions/close together BUT can move past each other, PRETTY STRONG forces, PRETTY HIGH density, A LITTLE compressibility, TAKES the shape of its container, YES shape + volume, vibrational AND rotational energy, SOME diffusion, and A LITTLE expansion when heated.

3. Gases - Super far apart/no orderly arrangement/free, ALMOST NO forces, VERY LOW density, A LOT of compressibility, FILLS the entire shape of a container, YES shape + volume, vibrational AND rotational AND translational energy, A LOT of diffusion, and A LOT of expansion when heated.

Describe the differences in properties of metallic, molecular, ionic, and covalent network solids (12)

1. Metallic - (Aluminum, copper, gold, silver, iron, and tin), silver/gray shiny solid, negative sea of electrons attracted to positive stationary ion, ranges from weak to strong (the more positive the metal cation, the stronger the bond), soft to hard, malleable doe to moving sea of electrons, ranges from low to high (melting and boiling points), high conductivity, insoluble, and does not dissolve.

2. Ionic - (Sodium chloride, NaCl, potassium chloride, KCl, magnesium sulfate, and MgSO4), little white crystals, positive and negative ions, opposite charge attraction between ions, strong, hard, brittle and cleave, high (melting and boiling points), no conductivity, mostly soluble, and conductive solutions/solution conducts.

3. Molecular - (Wax, butter, Cristo grease, sugar, plastic, tar, and asphalt), differently colored globs, molecules, hydrogen bonding/dipole-dipole/dispersion forces, medium to weak, soft, malleable, low (melting and boiling points), no conductivity, mostly insoluble, and if dissolves WILL NOT conduct (unless it is an acid).

4. Covalent Network - (Diamond, graphite, silicon (Si), quartz, and sand (SiO2), rock or sand, nonmetal atoms, covalent bonds, SUPER STRONG in 3D CNS and weak between layers in 2D CNS, super hard in 3D CNS soft in 2D CNS, brittle if can be broken for 3D CNS, supper high for 3D CNS and lower for 2D CNS, little to none conductivity, insoluble, and does not dissolve.

Define an allotrope (12)

• Allotropes are 2 or more different physical forms in which a single element can exist.

List and explain several of water’s unique properties especially those involving hydrogen bonding (12)

• Water formula is H2O, water molecules have a bent shape, water is polar (has both a positive and negative end), water is the most abundant substance on the earth’s surface, water exists as a liquid at room temperature, water has very high specific heat, ice is less dense than liquid water, water has a high surface tension, AND water is the universal solvent.

Determine the name of the phase change that occurs when a substance changes state of matter and whether the substance would usually gain or lose heat energy to make that change (12)

1. Solid → Liquid (Melting/gains heat)

2. Liquid → Gas (Vaporization/gains heat)

3. Solid → Gas (Sublimation/gains heat)

4. Liquid → Solid (Freezing/loses heat)

5. Gas → Liquid (Condensation/loses heat)

6. Gas → Solid (Deposition/loses heat)

Describe the difference between the following types of intermolecular forces. Include how you know which type you have and their relative strengths. (12)

1. Hydrogen bond: A strong attraction between a hydrogen atom bonded to N, O, or F. (H2O, NH3, and HF). Strongest IMF (but still weaker than covalent bonds).

2. Dipole-dipole forces: Attraction between polar molecules due to the positive end of one molecule attracted to the negative end of another. (HCl and SO2). Moderate (weaker than hydrogen bonds, stronger than dispersion forces).

3. London dispersion forces: Temporary dipoles caused by random electron movements in all atoms and molecules, even nonpolar ones. (Present in all substances, CH4, I2, and noble gases). Weakest, but can be stronger in large, heavy molecules.

Determine the strongest type of intramolecular/intermolecular force between 2 representative particles of each of the following and rank their relative melting and boiling points. (12)

1. HF - Hydrogen bonding, polar, and high melting/boiling point.

2. Ne - London dispersion forces, nonpolar, and very low melting/boiling points.

3. NH4Cl - Ionic bonds/compound, not covalent, and very high melting/boiling point.

4. PBr3 - Dipole-dipole forces, polar, and moderate hydrogen bonding.

5. RANKED highest melting/boiling point: Ne (Weak London Dispersion), PBr3 (Dipole-Dipole), HF (Hydrogen Bonding), and NH4Cl (Ionic bonding).

Which state of matter changes its shape but not its volume when moved from container to container? Why? (12)

1. Liquid changes its shape, BUT not its volume.

2. Liquids flow to fit the shape, but DOESN’T compress or expand to fill the space like gasses do.

List the four types of solids. (12)

• Metallic

• Ionic

• Molecular

• Covalent network.

How do the four types of solids differ in terms of solubility? How do they differ in terms of conductivity in their solid state and solution state? (12)

1. Solubility: Metallic (insoluble), ionic (mostly soluble), molecular (mostly insoluble), and covalent (insoluble). 

2. Conductivity: Metallic (does not apply, does not dissolve), ionic (solutions conducts), molecular (if dissolves, will not conduct unless it is an acid), and covalent network (does not apply, does not dissolve).

What does it mean to say that water has a high specific heat? (12)

It takes a lot of energy to raise the temperature of water compared to most other substances.

Draw a picture depicting 6 water molecules in its solid, liquid, and gaseous state. Your drawing should reflect their relative destinies. (12)

[intentionally left blank]

On a typical phase change graph, why are the phase changes horizontal (meaning the temperature is constant) even though the substance is still gaining or losing energy? (12)

1. Temperature is staying constant, even though energy is still being added or removed.

2. During a phase change, the energy being added is used to BREAK or FORM intermolecular forces. NOT speed up the particles.

Why is ice less dense than liquid water? (12)

1. It is due to the particles arrangement in a solid like ice compared to a liquid like water.

2. In the ice, the molecules are forming a hexagonal shape which has lots of spaces compared to the molecules in liquid water, which are so easy to move around.

What is the name of the phase change when a gas turns into a liquid? When a solid turns into a gas? (12)

1. Gas → liquid = Condensation.

2. Solids → gas =  Sublimation.