D.S. Chapter 15

An Element of Madness

William Crookes came from a large family and was in England's premier scientific club but when his brother Philip died he turned to the supernatural to try to find comfort. Even after his earlier findings in the study of selenium and his discovery of thallium and then later giving the first suggestion of isotopes, his fellow scientists called him crazy and attacked his character. Stanley Pons and Martin Fleischmann let their whimsical sides get the better of them when they ran a current through water with hydrogen that have an extra neutron and a palladium electrode. Palladium takes in 900 times its volume of hydrogen and when it took in the heavy hydrogen temperatures spiked erratically so that the duo thought they had discovered cold fusion available at room temperature. Skeptics rooted out their claims by finding the two had overlooked procedures and their findings were dismissed within 40 days. But the spirit of cold fusion and finding cheap clean energy didn't die even through countless counter experiments and results. On the opposite end of the spectrum, Wilhelm Röntgen actually tried to prove himself wrong when his results made him think he was going mad. When playing with a beam of electrons in a Crookes tube, he thought he was hallucinating when he saw a barium plate light up even though the tube was darkened. Playing with objects, he came to the conclusion he'd gone mad when he was able to see through things, even his own hand. He had discovered x-rays but refused to be revolutionary so he experimented till he couldn't prove himself wrong and he backed his findings up to every other scientist that was cruel to his new idea.

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Unit 4 lesson 23 & 24

Lesson 23 - Precipitation Reactions

Precipitate- a solid produced in a chemical reaction between two solutions

Substances with low solubility tend to form precipitates in aqueous solutions

Most reactions involve double exchange reactions with ionic compounds where the cations exchange anions.

Lesson 24 - Mole Ratios
Coefficients in chemical equations refer to the number of units like molecules, moles, or ions that are combining.

Mole ratio- ratio represented by the coefficients in a chemical equation showing how many units of each substance must combine to make the maximum amount of product.

Reactants combined in a imperfect mole ratio run out of one while leaving behind more of the other:

        - limiting reactant - runs out

        - excess reactant - leaves more behind

When comparing the two reactants, compare the moles to find out which is limiting and which is excess. Don't use the coefficients.

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Disappearing Spoon Chapters 13

13- Elements as Money

Elements and money have always been intermingled, especially metallic elements. From Midas, who turned everything he touched into "gold", which was really just gold-hued brass that shined brighter than the Greeks' bronzes and so grew into myths of magic, to the Irish Patrick Hannan who was tricked into starting the fool's fool's gold rush in 1893 only to discover that the miners were discarding the actually valuable tellurium which is one of the very few elements that combines with gold. The miners soon tore apart the town they had built to get at the telluride-infused bricks. In 540 BC was the creation of a real currency system by the Lydian king Croesus who separated electrum into silver and gold coins. But a real currency system brings those who want to create their own money through counterfeiting. Isaac Newton even played a role in bringing in the wrongdoers in the 1600s. After that came paper currency with a whole new level of counterfeiting. The government needed to rival it so they used europium dyes which can emit fluorescent colors but with a receiver that absorbs the light causing europium electrons to stir and jump to higher energy levels emitting the light but dampened. This allows officials to pick out the real money under certain lights thus combatting the counterfeiters. Metals markets are always some of the most stable and long term sources of wealth. In 1886 Charles Hall discovered a way to separate aluminium (the most valuable substance at that time) from oxygen by running an electrical current through a liquid with dissolved aluminium which no one previously had figured out to do. He created an aluminum empire and made millions on the metal we use so commonly today.

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Unit 4 Lessons 21 & 22

Neutralization Reactions

• A neutralization reaction where adding acids and bases together neutralizes the solution producing an ionic salt compound and water
• Can be described as a double exchange where 2 compounds exchange cations

Ex: H2SO4 + Mg(OH)2 —> 2H2O + MgSO4
Practice Problems
7. C & D
8. B

Titration

    - procedure where a neutralization reaction is monitored with an indicator to get the unknown concentration
           - equivalence point is reached in a titration between a strong acid and a strong base , # of moles of H+ ions equals # of moles of OH- ions
Practice Problems
3) 1L of NaOH
5) a) acidic b) neutral c) basic

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Unit 4 Lesson 20

Dilution

This means that 8 is ten times more basic than 7 is one hundred times more acidic than 7.

You can add water to a solution to dilute it.

• In an acidic solution, adding water increases it's pH closer and closer to 7
• In a basic solution, adding water decreases the pH closer and closer to 7
• You can't reach a pH of 7 by simply diluting the solution with water and so you can't change an acid into a base or vice versa.

Practice Problems

5) because it was diluted so the pH decreased

7) a) .075 mol b) .068 M c) pH 1.17

 

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Unit 4 Lesson 19

[ H+] and pH

Acidity is determined by the concentration or Molarity of H+ ions n moles per liter. This concentration is symbolized by [H+].

The greater the concentration of H+ ions the lower the pH and it is more acidic.

The hydrogen ion concentration is directly related to the pH of the solution.

The pH number is equal to the exponent just without the negative. This is only true in scientific notation when the coefficient is 1.0.

pH is connected to [H+] through the logarithmic formula pH = -log[H+]

Bases' pH can also be determined because bases contain H+ concentrations. The H+ concentration in scientific notation and the exponent subtracted from 14 is the concentration of OH- ions.

Ex: water - [OH-] is 1.0 X 10^-7 and [H+] is 1.0 X 10^-7 because 7+7=14

Formula: [H+][OH-]= 1 X 10^-14

Practice Problems

3. a) pH 4 b) pH 12 c) pH 6

4. a) pH 2.85 b) pH 13.38 c) pH 7.22 d) pH .82

 

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Unit 4 Lesson 18

Acid-Base Theories

Acids

• Made up of main group nonmetals like carbon, oxygen, fluorine, and chlorine
• All have hydrogen
• Break apart to form one H+ and an anion

Bases

• Contain metal atoms and an hydroxide ion, OH-
• Except for hydroxides, the name isn't helpful to identifying them as bases

Changing definitions of acids and bases:

• Arrhenius definition- an acid is any substance that adds a hydrogen ion to a solution. A base is any substance that adds a hydroxide ion to a solution.
• Bronsted-Lowry definition- an acid is a proton donor and a base is a proton acceptor

Acids add H+ (one proton) to the solution

Bases add OH- to the solution

Strong Acids and Bases- dissociate completely in a solution to form only ions. They are good conductors of electricity.

Weak Acids and Bases- only partially dissociate in a solution. Less corrosive

Practice Problems
4. a) acid b) acid c) base d) acid e) acid f) acid g) acid h) base
6. a) 20 OH- ions

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Unit 4 Lesson 17

Acids and Bases

• Are corrosive and toxic
• Classified according to their observable behavior
• Change the color of indicators
• Water is not acidic or basic so it's neutral

Indicator- a molecular substance that changes color when it comes into contact with an acid or a base
The pH scale

The colors on the pH scale are associated with a "universal indicator" and every color has a specific number known as the pH.
Numbers on the left leading up to 7 are pHs relating to acids, 7 is neutral like water, and the numbers on the right after 7 refer to bases.
The further away from 7 on either side the potentially more toxic the acid or base would be.

Practice Problems
2. The pH scale is a number line that assigns numbers from 0-14 to acids or bases
5. a) acid b) base c) base d) neutral e) base

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Disappearing Spoon Chapter 10

The first thing talked about in this chapter is the fact that some elements do things we wouldn't expect them to do. For example, silver and copper are "self-sterilizing" which means that bacteria that comes into contact with them absorb their atoms and so their metabolisms are disrupted and they die. This explains why they are so commonly used in public places and why we have copper coated coins. Some are used for medicinal purposes like vanadium as a spermicide and gadolinium which is used in MRIs because gadolinium has the maximum number of unpaired electrons and so it is more magnetized than any other element. This combined with tumor targeting agents makes it easier to locate the tumor on the MRI. Also, gadolinium has the potential to fight cancer better than chemo because if gadolinium absorbs neutrons it turns radioactive and in a controlled situation, could destroy the tumor without destroying healthy cells around it. Louis Pasteur discovered in 1849 that almost all proteins in life forms are "left-handed" meaning they bend light clockwise when dissolved and that nature prefers to have molecules of all the same handedness and not a mixture of both. He also developed pasteurization and the rabies vaccine. In 1935 Gerhard Domagk used a red dye or Prontosil to cure his daughter of streptococcal and then Prontosil was examined by scientists at Pasteur Institute in France and found that mammal cells split it in two to create sulfonamide. Sulfonamide inhibits produstion of folic acid used in cells to replicate DNA and reproduction so while humans get folic acid from food, bacteria can't make their own so they can't reproduce. Domagk earned the Nobel Peace Prize in 1939 but was brutalized by Nazis and the Gestapo and later saved soldiers with his drugs, including Winston Churchill.

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Unit 4 Lesson 16

Mystery Solutions

Molarity can be used to identify a toxic substance.

• A substance dissolved in water adds mass to the solution
• 1 mol of a substance can have different molar mass than another
• Weighing different solutions with the same concentration can differentiate between them

Ex: 200mL 1.5M NaCl, 1M KCl, 1M CaCl2 which has the most mass?
NaCl - 58.5g –> .2L • 1.5 = .3mol • 58.5g = 17.64g
KCl - 74.5g –> .2L • 1 = .2mol • 74.5g = 14.9g

CaCl2 - 111g –> .2L • 1 = .2mol • 111 = 22.2g

CaCl2 has the most mass. This means the three solutions have the same concentration but since calcium chloride has the most mass then the heaviest solution will be the chloride solution, the second heaviest will be potassium chloride, and the least is sodium chloride.

 Practice Problem

7) a would weigh the most because it has the most amount of moles compared with mass

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Unit 4 Lesson 15

Preparing Solutions

You can find specific grams of solids to make specific molarities and find the concentration with all of the equations learned in this unit.

Ex: .01L of 0.5M of solution of NaBr. What is the mass?

Practice Problems

5) a. 10 L  b. .3 L  c. .18 L

7) 20g of glucose 

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Unit 4 Lesson 14

Molecular views

• The concentration of a solution doesn't change with the size of the sample
• Concentration is a measure of density of moles per unit of volume
• Total number of molecules does change with size
• Moles = k • volume of solution (k is the molarity) can calculate the # of moles in a sample
• When calculating the number of moles of particles in an ionic solution, it is necessary to take into account all the ions in the formula

Ex: ionic solution of NaCl with 1.0M in 1L means there are 1 mol of each NaCl
Ex: CaCl2 solution 100mL and 2.5M

• First find number of moles - 2.5 • .1L = .25 mol CaCl2
• This means that each ion has a mol of .25 so there is .25 mol of Ca and .5 mol of Cl because there are two of them
• In total .25 + .5 = .75 mol of ions

Practice Problems
1) Because volume and density/concentration are measured differently.
3) a. 1 L Glucose and sucrose because they has the same molarity and volume so the number of moles are the same. .
b. they all have the same concentration 1.0M
c. 1 L Sucrose because it has the same molarity and more volume than 500mL of sucrose and each molecule has more mass.

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Unit 4 Lesson 13

Solution Concentration

Solution - mixture of two substances that is uniform throughout

Solute - substance dissolved in a solution

Solvent - substance the solute dissolves in

Saturated solution - solution containing the maximum amount of solute for a given amount of solvent

Concentration - amount of solute dissolved in a specific volume

Can measure the concentration of a solution by finding the molarity

Molarity - concentration of a solution expressed in moles of solute per liter of solution

• Molecules move from areas of high concentration to areas with lower concentration

Practice problems
5) c,a,b

6) a(1M), b(2M), c(4.9M) 

9) A

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Unit 4 Lesson 12

Comparing Amounts

Using moles to compare toxic substances is preferred to using the masses because moles allow you to compare how many molecules of one toxic substance are equal to the mass of the number of molecules in a different toxic substance.

2 substances with = mass and = # of molecules and = toxicity can still differ in how much of which will effect you the most because the substance with the larger molar mass needs less of it to make up the same amount as the substance with a lower molar mass. This means the larger the molar mass the better.


Healthy effects due to toxic exposure depend on both LD50 and the amount of the substance.

Smaller lethal doses (LD50) means the more toxic the substance, but even if you don't consume the lethal dose, it doesn't mean there won't be any long term effects.

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Unit 4 Lesson 11

Mass-Mole Conversions

You have to convert mass into moles to find out the number of molecules/atoms

• Mass of the number of moles is atomic mass • number of moles
• # of mols of Carbon in 3.0 mol of C9H8O4?

- 27 mol of Carbon because 9 mol of carbon times 3.0 mol of the compound is 9 • 3 = 27 mol.
# of moles of H in 160g of NH3?

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Unit 4 Lesson 10

Molar Mass

Molar mass is the mass of 1 mol found on the periodic table as the atomic mass.

How many grams of Cl in 100g of CaCl?

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Unit 4 Lesson 9

Avogadro's Number

• 1 mol = 6.022 x 10^23

Scientific notation

• The decimal always has one number to the left
• Positive --> move the decimal point to the right
• Negative --> move the decimal point to the left

The mass of 1 mol of a substance is called the molar mass

• Atomic mass given on the periodic table is = to the mass of 1 mole of atoms of the element in grams
• Molar mass allows you to convert between moles of atoms and grams of atoms

Ex:

Practice Problems

4) a. 14  b. 20.1797  c. 35.5  d. 63.5

5) a. Carbon  b. iron  c. Gold  d. Gold

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Unit 4 Lesson 8

Counting by Weighing

Weighing really lightweight objects to help find the mass is a lot more difficult and less accurate than when weighing heavier objects. To accurately weigh one you must:

• Weigh a group of the identical objects
• Divide that weight by the number of objects
• Gives an average weight for one

Knowing the average weight of one object means you can pretty accurately determine the number of the objects in a large group by weighing the larger group and dividing that by the average weight.

Percent Error

Percent error allows you to see how close your answer is to the actual answer.

Formula: |(observed value - actual value)| • 100

actual value

 Practice Problems
4) the rice because rice is generally smaller than beans so more of them would be needed to equal 50 grams of beans.
5) 740 marbles has more mass because they are bigger and so take up more mass

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Unit 4 Lesson 7

Lethal Dose

Toxicity

Lethal Dose (LD50) - amount of an ingested substance that kills 50% of a test sample of animals.

• Expressed in mg/kg of body weight
• 1 kg = 2.2 lbs

Toxicity depends on 2 qualities: amount of substance and mass of the organism

Everything can be toxic if you take in enough of it

The smaller the LD50 the more potentially dangerous

Practice Problems

2) toxicity depends on weight because the more someone weighs, the more of the toxic substance they need to be as affected as a lighter person.

 

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Unit 4 Lesson 6

Types of Reactions

Combination - A + B ---> AB

• several reactants combine into a single product

Decomposition - AB ---> A + B

• compound breaking down

Single Exchange - A + BC ---> AC + B

• Compound breaks apart with 1 part combining with the other reactant

Double Exchange - AB + CD ---> AD + CB

• Both reactants break apart and recombine

Practice Problems
6) Li(s) + 2HCl2(aq) ---> H2(g) + LiCl4(aq)
7) AgNO3(aq) + NaOH(aq) ---> NaNO3(aq) + AgOH(s)

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Unit 4 Lesson 5

Atom Inventory

Balancing Chemical Equations

Balanced chemical equations show the true mathematical relationship between the reactants and the products in a chemical reaction.

• When balancing, start with atoms that only show up once on each side of the equation
• You can only change the coefficients
• Coefficients indicate how many "units" of an element or compound are present

Ex: __N2(g) + __H2(g) ---> __NH3(g) this equation is unbalanced because there are 2 nitrogen atoms and 2 hydrogen atoms in the reactant side but there is only 1 nitrogen and 3 hydrogen in the product. To fix this, change the coefficients.
N2 + 3H2 ---> 2NH3 Now this equation is balanced because there are 2 nitrogen atoms on both sides and 6 hydrogen atoms on either side.
Practice Problems

3) a. Make three loaves of bread because 6 divided by 2 is 3
    b. because if you multiply all the ingredients by 3 it's balancing both sides of the recipe to use all six bananas.

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Unit 4 Lesson 4

Conservation of Mass

• Can't create or destroy matter
• Mass (# of atoms) and weight (force of gravity) are different
• Gases have mass

If one of the products of a chemical reaction is a gas, the mass of the products will be less than the mass of the reactants, unless you trap the gas.

Mass Change

• Individual atoms are conserved in chemical reactions and physical changes. The number of atoms of each element remains the same from start to finish.
• Mass is conserved in chemical reactions. The total mass of the products equals the total mass of the reactants.

Practice Problems
4) when an ice cube melts, what quantity changes? C- its volume
7) trap the gas and ash left and weigh it.

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Unit 4 Lesson 3

Physical Vs. Chemical Change

Physical Change - change in matter in which a substance changes form but not identity. These can also include color or temp.

• Ex: H2O(l) ---> H2O(s)

Chemical Change - change in matter resulting in the formation of a new substance or substances with new properties.

• Ex: 2Na(s) + Cl2(g) ---> 2NaCl(s)

You're not always able to see if a physical change is accompanied by a chemical change simply through observation. You need a chemical equation.

Dissolving of a substance can either be physical or chemical but is considered physical.

Practice Problems
1) physical change is not a change in identity of the substance while a chemical change is a change in identity by rearranging the atoms.
6) a. Chemical because the product is not identical to the reactants b. Physical because only the phase of the substance changes

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Unit 4 Lesson 2

Making Predictions

Observing Change

When a substance changes phase or dissolves, its chemical formula does not change.

When you look at a chemical equation, it can tell you the different kinds of changes going on like changes in phase or identity of the substance.

Ex: CaCl2(aq)+ 2NaOH(aq) ---> Ca(OH)(s) + 2NaCl(aq)

For this chemical equation you start of with two aqueous reactants, but when they undergo the reaction you can tell that there was a change visually because now one of the products is a solid that you would be able to see. The equation would also allow you to see which substances broke up and rearranged to combine into a solid. You wouldn't be able to know this without seeing the chemical equation.

Some things a chemical equation alone can't tell you is if there were any changes in temperature or color after or during the reaction or how quickly it happened.

Practice Problems

4) a. NaCl(s) ---> NaCl(aq) b. MgS(s) ---> Mg(s) + S(g) c. Ti(s) + O2(g) ---> TiO2(g)

5) a. Two aqueous solutions combining leaving behind water and emitting chloramine gas and aqueous sodium hydroxide b. two aqueous solutions combining to produce hydrazine gas, aqueous sodium chloride, and water

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Unit 4 Lesson 1

Toxic Reactions

Chemical Equations

Chemical formulas

• Represent changes in matter using symbols and formulas.
• Describe what happens when a single substance is changed or two or more are combined causing a change.
• Substances that you start with are called reactants and when the change takes place you end up with products.

Ex Chemical Equation: NaCN(s) + HCl(aq) ---> NaCl(aq) + HCN(g)The interpretation of a chemical equation is telling you exactly what is happening in the reaction.

The interpretation of the equation above(colors correspond): Solid sodium cyanide reacts with hydrochloric acid to produce aqueous sodium chloride and gaseous hydrogen cyanide.

Some chemicals react negatively to substances in the body and are called toxins.

Toxins - substances that interact with living organisms and cause harm.

Toxins Enter the Body

• React with water in body
• Could be molecular, ionic, or metallic substances

Practice Problems
3) a toxic substance is something that enters the body and then reacts with substances in the body where the products are harmful.
6) Forming solids that clog places in the body. Bad metals compete with good metals that the body needs. Acidic products that damage tissue.

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Unit 3 Summary

Unit 3 was all about how gas pressure, density, temperature, and the number of molecules all relate to one another to give make up the gas laws. These gas laws have significant importance to weather patterns and formation.

Gas Laws

Charles's Law: k=V/T constant k = volume/temperature

Boyle's Law: k=PV constant k = pressure x volume

Gay-Lussac's Law: P=kT pressure = constant k x temperature

Combined Gas Law: k=PV/T constant k = (pressure x volume)/temperature

Ideal Gas Law: PV=nRT (pressure x volume = (number of moles/molecules) x (constant R 0.082) x (temperature)

• For all the gas laws, the temperature has to be in degrees Kelvin

A lot of the weather we experience has to do with phase changes water goes through

• Evaporation- the phase change from liquid to gas
• Condensation- the phase change from gas to liquid
• Freezing- the phase change from liquid to solid

Density is a recurring factor in all aspects of weather including:

• humidity which is the water density in the air
• pressure because the more dense the number of molecules in the air, the higher the pressure
• The warmer the air is the higher the water density can be and exceeding that maximum results in precipitation

Practice Problems

 

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Lesson 19

Hurricanes

• Destructive storms characterized by strong winds and rainfall
• Tropical Depressions---> tropical storms---> hurricanes

5 categories determined by strength for hurricanes are from 1-5 --> least-most intense

Tropical storms - a lot of warm water evaporates

• Moves over warm water and evaporation increases

Water vapor density is related to temperature

As temperature increases, so does the water vapor density.

This means that colder temperatures have a lower maximum density where the density is 100%

 

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Lesson 18

Humidity and Condensation

Humidity - density of water vapor in the air; dependent on temperature and pressure

• measure of the amount of water vapor in the air
• Temperature that water condenses indicates how much water vapor is in the air

When the temperature is colder then the water vapor in the air is less dense and as the temperature rises, the density increases.

Relative Humidity - amount of water vapor in the air compared to water vapor possible for a specific temperature; indicated as a percent

• Upper limit to amount of water vapor that is possible at a given temperature

Practice Problems

5) 2.2 mol/1000 L

7) 1.6/4 = .4 mol/1000 L

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Lesson 17

Ideal Gas Law

• Relates temperature, pressure, volume, and number of moles of particles
• Formula: PV=nRT
• R is the constant and R = 0.082 • atm/mol • K
• R is the same for all gases
• R can change with different units like changing Liters to Milliliters

To find the total number of molecules in a sample of gas, take the number of moles and multiply by (6.022 • 10^23)

Practice Problems

1) the ideal gas law is: pressure x volume = number of molecules or moles x the constant 0.082 x temperature

 

2)

 

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Lesson 16

Avogadro's Law

To count the number of molecules in a specific volume of gas, the unit is counted in moles.

• 1 mole = 6.022 x 10^23 (also called Avogadro's number)
• 1 mole at standard temperature of 273°K and standard pressure of 1 atm occupies a volume of 22.4 L
• This standard temperature and pressure is abbreviated STP

Avogadro's Law - If two gases have the same pressure, volume, and temperature, then they have the same number of gas molecules independent of the identity of the gases.

Practice Problem

5) 8.0 g of helium has more atoms because 8g is two atoms and 40g of argon is only one argon atom.

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Lesson 15

Pressure and Number Density

The number of molecules in a gas is directly related to the pressure.

When the gas pressure increases, this means that there was an increase in the number of gas molecules per unit of volume.

• Number of gas molecules is represented by the letter n.

Formula: P=k(n/V)
Number Density- the number of gas particles per unit of volume which can be found by dividing the number of molecules by the volume - n/V

You can determine the pressure by measuring the difference in height of a liquid.

Practice Problems

1) decrease in air pressure with increasing altitude comes from the fact that the number density of molecules in the air decreases with the rises in altitude, ultimately lowering the gas pressure. 

6) a. B has the least air pressure because even though it has the same numbe of molecules as A, it's volume is larger making it less pressure per liter. 

A has the next largest pressure because even though it's volume is the same as C, there are fewer molecules, giving it a lower number density. 

C has the largest gas pressure because it is the small volume with the most molecules, giving it the highest number density, so a higher pressure. 

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Lesson 14

High and Low Air Pressure

Clouds are just water droplets suspended in the air and to form there needs to be moisture in the air

Formed from:

• Conditions of low temperature and pressure
• In warm air mass- the water vapor in the air rises and cools off
• Change in pressure
• Changing phase from vapor to droplets

Clouds under go changes in pressure and temperature but the volume stays the same

-as pressure increases, the temperature also increases

Warm air rises

Low Pressure:

• Associated with fronts, storms, clouds, and precipitation
• Warm and cold air meets and the warm air rises which leaves behind low pressure (since there is low temp.)
• This low temperature brings cloudy and rainy weather

High Pressure:

• Clear skies
• Denser air is sinking, inhibiting rain and clouds

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Lesson 13

Combined Gas Law

When all three variables of temperature, pressure, and volume are variables and none stay constant, you need to use the Combined Gas Law.

Formula

• k=(P)(V)/ T - the proportionality constant k equals the original pressure multiplied by the original volume all divided by the original temperature.
• After finding this proportionality constant, you can plug it into the equation along with the rest of your changed values to find either the new pressure, volume, or temperature.

Changing gas pressure has more of an effect on volume than results that may have come from changing the temperatures.

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Lesson 12

Molecular View of Pressure

Gas pressure is caused by the movement and collision of molecules

• Collision of molecules into the container only
• Increase in temperature causes an increase in pressure because the molecules hit the container faster and with more force
• Decrease in volume causes an increase in pressure because the molecules are forced into a smaller space and hit the container more often

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Lesson 11

Gay-Lussac's Law

- pressure of a given amount of gas is directly proportional to the temperature if the gas volume and amount of gas do not change and if the temp. is expressed in degrees Kelvin.

Changing pressure can depend on the type of container the gas is in:

Flexible Container- changing temperature or pressure changes volume of gas.

-This comes from the container allowing the gas to expand the container walls out

Rigid Container- increasing temperature causes pressure to increase

- since the container won't allow the gas volume to expand, it can't relieve some of the pressure so the pressure rises along with the temperature.

Formula

• k=P/T - constant k equals the original pressure divided by the original temperature
• V is missing from the equation because the volume is not changing

 

 

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Lesson 10

Boyle's Law

In Boyle's Law the relationship between gas pressure and gas volume are inversely proportional meaning that instead of one increasing, causing the other to increase, when one increases then the other decreases.

inverse proportion - two variables are inversely proportional to each other if one variable increases when the other decreases.

Formula

• k=PV
• k is the proportional constant that you find by multiplying the original pressure and volume
• You then solve either for the new pressure or the new volume by plugging in the k value
• The term missing from this equation is the temp. Meaning that it is the term that stays the same while pressure and volume change

 

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Lesson 9

Air Pressure

-force per unit area exerted on objects as a result of gas molecules colliding with those objects

Pressure - force applied over a specific area

- gas pressure caused by gas molecules striking objects or the walls of a container

Two Types

• Air pressure trapped inside a container
• Air pressure from the atmosphere outside

- atmosphere: mixture of gases surrounding you

- atmospheric pressure: air pressure that's always present on earth as a result of air molecules colliding with the surfaces of objects

Sea level has 14.7 lb/in squared of air pressure or 1 atm.

Practice Problems

3) the balloon would instantly expand until it popped because of the lack of outside air pressure

5) the cabin pressure and the pressure inside your head is a lot more than the air pressure outside the plane.

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