MEASUREMENT IN CHEMISTRY
edited by Kati "Marie" West
co-editors:Nic Cunna, Delia Calderon, Brett Chatfield, Randy Melanson, Dan Lynch, Abbey Salvas, Siri Devlin, Ben Ross

Hi guys! This is your editor speaking~! I've set everything up, so when you post your part of the outline, put it right under your name inside your section (in black and not all underlined, please) so I can keep track of who's doing their job! When a whole section is finished I'll turn the title purple, just because I'm OCD like that. :) If you find anything that might help anyone with the unit, feel free to post that under Misc. at the bottom. Happy studying!

1.1 What is Chemistry
p.7-9 Austin Burlone

p. 10-11 Nic Cunna
Why Study Chemistry?
- Chemistry can have an impact on all aspects of your life.
- Chemistry can be useful in explaining the natural world, preparing people for career opportunities, and producing informed citizens.
Explaining the Natural World
- People are born with curiosity and Chemistry can help you satisfy that curiosity
- It can help you understand why yeast makes dough rise of why eggs get firm when they are cooked
Preparing for a Career
- Throughout the book there will be inferences to careers that knowledge of chemistry is beneficial to have.
- For instance having a good background in chemistry can help as a firefighter because knowing what chemicals put out certain types of fires is helpful in getting the job done and people safe.
- Turf managers and photographers also need to have some background or knowledge in chemistry
Being an informed citizen
- Industry, Private foundations and federal government provide funds for scientific research and the amount of funds available is what determines the direction of research. The fund distributors have to balance the importance of a goal against the cost. This creates competition for funding.
- Space exploration would not have happened without government funding. Some object that it would have been better to spend the funds on finding a cure for cancer rather than space exploration. Yet, then people also object pointing out that Space Exploration has led to numerous outbreaks of research and progress in other fields.
- When it comes to technology there is no one correct answer. Knowledge of Chemistry and other sciences can help you evaluate the data presented, arrive at an informed opinion, and take appropriate action.


1.2 Chemistry Far and Wide
p. 12-14 Andrew Marcotte

p. 15-19 Delia Calderon

Agriculture

-It is important to ensure that land used for agriculture is as productive as possible.
-Chemist help develop more productive crops and safer, more effective ways to protect crops.
-Productivity
Measured by the amount of edible food that is grown in a given unit of land.
Poor soil quality, lack of water, weeds, plant diseases, and pest decrease productivity.
Chemist can recommend ways to improve soil and develop plants that are more likely to survive a drought or insect attack.
-Crop Protection
In the past chemicals used to attack insect pests were nonspecific; the chemical would kill pest as well as useful insects.
Chemists are able to create chemicals that are designed to treat the specific problem.
The chemicals are often similar to the chemical the plants produce for protection as well as chemicals produced by insects.

The Environment

-A pollutant is a material found in the air, water, or soil that is harmful to humans and other organisms
-Chemist help to identify pollutants and prevent pollution.
-Until the mid-1900s lead was used in many products. A study done in 1971 showed that the level of lead that is harmful to humans is much lower than had been thought, especially in young children.
-Some products containing lead were banned within the next decade such as lead paint and in gasoline and public water supplies.

The Universe

-To study the universe, Chemists gather data from afar and analyze matter that is brought back to earth.
-Moon rocks were used to suggest that oceans of molten lava once covered the moons surface because they were similar to rocks formed by volcanoes on earth.
-The chemical compositions of rocks and soil on mars indicate that the site was once drenched in water.


1.3 Thinking Like a Scientist
p. 20-23 Brett Chatfield

Alchemy

-The word Chemisty comes from the word Alchemy.
-Alchemy was the name for the early chemisty and was divided into the areas of practical alchemy and mystical alchemy.
-Practical focused on working with metals, galsses, and dyes.
-Mystical focused on concepts like perferction

An Experimental Approach to Science

-In the 1700s Antoine-Laurent Lavoisier did work to improve chemisty
-He solved many questions about how and why things burn
-During the French revolution he had a postition in finance so he could continue his work in finances
-Although he was trying to help, he was a target of the people

Scientific Method

The Scientific Method is a logical, systematic apprach to the solution of a scientific problem

Making Observations

-When you use your senses to make an observation, you make an Observation

Testing Hypothesis

-A hypothesis is a proposed explanation for an observation
-An experiment is a procedure that is used to test a hypothesis
-A manipulated variable is the independent variable
-The responding variable is known as the dependent variable

Developing Theories

-A theory is a well tested explanation for a broad set of ovservations
-In chemistry one theory addresses the fundamental structure of matter
-When scientists say a theory can never be proved, they are not saying that the theory is unreliable

Scientific Laws

-A scientific law is a concise statement that summarizes the results of many observations and experiments

p. 24-27 Elaney Marcotte
Collaboration and Communication
 -individuals must collaborate for the good of the team.
-Scientists collaborate and communicate to increase the chance of a successful outcome.

Collaboration
-Scientists around the world collaborate. It is sometimes necessary to bring together different people in order to solve a problem. Each scientist can bring different knowledge and ideas.
-Industries may give funding to a group of scientists to do research together. The scientists provide ideas and expertise, and the industry can make a profit from the discoveries and the ideas of the scientists.
-Conflicts can arise when scientists come together. Conflicts can arise over a use of resources, amount of work each person does, who receives credit for the work, and what and when to publish.

Communication
-Scientists communitate with each other in many ways. Scientists used to communicate through letters, societies to share findings, and in published journals. Scientists now communicate face to face, through email, over the phone, at international confrences, and in published journals.
-Scientists publish their works and findings in journals. These are only published after being reviewd by experts. If work is not well founded or is inaccurate, then the journal will not be published.
-The Internet is a source of information for scientists and for all people. Anyone has access to it which helps make communication easier. The Internet also allows anyone to post information on it which means that information on the Internet might not always be correct. People need to check that the information they are using is approved by an expert so that they know it is correct.

1.4 Problem Solving in Chemistry
p.28-30 Marissa Chura
Skills Used In Problem Solving
-Problem solving may involve the use of a table, graph, or other visual.
-The skills used to solver problems are the same skills used in everyday life.
-Problem solving involves creating and following a plan to get the answer.

Solving Numeric Problems

Most word problems in chemistry involve the use of math. This three-step technique for problem solving helps make it easier to work out the problem.

STEP ONE: ANALYZE
-Begin by analyzing the problem. Identify your starting point, or what information you already have, and your destination, or the information you need to find.
-Before doing any math, figure out what units your final answer should be in (meters, liters, etc.)
-Use a diagram, graph, or table help visualize the relationship between the starting point and the destination (optional).

STEP TWO: CALCULATE
-Figure out the equation you need to use to solve the problem.
-Depending on the problem, you may have to convert units or rearrange an equation. Make sure the equation you are using applies to the problem.

STEP THREE: EVALUATE
-Check to make sure your final answer makes sense.
-If the answer doesn't make sense, reread the problem and check your work for errors.
-Double check to make sure your answer is using the correct unit.

p. 30-32 Randy Meanson
Solving Conceptual Problems
Some problems ask you to apply concepts to new situations. Nonnumeric problems are labeled conceptual problems.

STEP ONE: ANALYZE
-Identify the relevant concepts.
-To solve a conceptual problem identify what is known and unknown.

STEP TWO: SOLVE
-To solve conceptual problems apply the known and unknown to the situation.
-Make a plan to get from what is known to unknown.


3.1 Measurements and Their Uncertainty
p. 63-65 Frank Morley

Using and Expressing Measurements

Measurement is a quantity that contains both a number and a unit,

-Measurements are needed to experimental sciences (Chemistry). So the correct measurements are needed.
-The units in Measurements are often in the International System of Measurements (SI)

-We will often have to use either very large or very small numbers. For this we will use scientific notation

Scientific Notation

-When using Scientific notation you move the decimal point until there is one whole number to the left of the decimal point
-There may be numbers other than 0s to the right of the decimal point, but for the most part it will be 0s.
-After you have done the steps above you count the number of decimal places you have moved and you set that as an exponent to 10.
-This will be multiplied by the whole number and then any number other than 0 that is after the whole number.
EXAMPLE: 102,000,000,000,000
-Move decimal point until one whole number is on the left- 1.02 / Then count decimal places in this case we have moved 14 places
-Add the number of decimal places moved as the exponent of 10 and multiply it by the 1.02 and we get 1.02x10 to the 14th power.
-For practice with Scientific notation go to page R56 of Appendix C in the book

Precision,Accuracy, and Error

Accuracy and Precision

Accuracy- How close the measurement comes to the true measurement of what is being measured.
-To evaluate accuracy you need to compare the measured value must be compared to the correct value.
Precision- How close a range of measurements are to each other (See page 64 for examples on precision and accuracy. Think of it like a dart board)
-To evaluate precision you must compare the values of two or more repeated measurements.

Determining Error

-accepted value- the correct value based on a reliable source.
-experimental value- the value that is measured in the lab
-There is often a difference between the experimental value and the accepted value.
-Error- difference between accepted value and experimental value.
Error= experimental value - accepted value.
-The magnitude of the error is often used to find the percent error
-Percent error= (l error l / accepted value) x 100%
absolute value of error divided by accepted value times 100%
EXAMPLE: Water is boiling, but the thermometer reads 99.1 degrees C.
-100 degrees Celcius is the accepted value for the boiling point of water, but the experimental value in this measurement is 99.1.
-ERROR: 99.1-100=-.9. -.9 is the error
-PERCENT ERROR: (l -.9 l / 100) x 100$
.009x 100%
.9%= Percent of error
-Measuring devices may not be accurate, so you will always have to check for error.

p. 66-68 Dan Lynch

Significant Figures in Measurements

-Significant figure - in a measurement includes all of the digits that are known plus a last digit that is estimated.
-If you are weighing some fruit at the store and they come out to in between 2.4 and 2.5 pounds. You notice that it is in the middle of these two digits and slightly closer to the 2.5. So you estimate that it is 2.46 pounds. In this example, 2 and 4 are numbers that are known and 6 is estimated, but still they are all significant figures.
-Measurements must always be reported to the correct number of significant figures because calculated answers often depend on the number of significant figures used in the calculation. This means that if you estimate the numbers that you use to calculations, then take more digits away from that they will be estimation.
1. Each nonzero digit in a measurement is assumed to be significant. 24.7, .743, and 714 all have three significant digits.
2. Zeros in between nonzero digits are significant. 7003, 40.79, and 1.503 all have four significant figures.
3. In the example .000000000995 has only three significant digits. It would be displayed as 9.95 x 10to the negative 10th power. The zeros in this are not significant, but they act as placeholders.
4. Zeros at the end are always significant. 43.00, 1.010, and 9.000 each have four significant digits.
5. Zeros at the end of a number like 3000 are not significant. To make sure they are considered significant use scientific notation 3.00 x 10 to the first power.
6. If you count 23 people in your class, that number has unlimited significant digits. For 60 min = 1 hour those exact calculations have unlimited digits.

EXTRA HELP, sorry this guy is so weird, but it is helpful

http://www.youtube.com/watch?v=5UjwJ9PIUvE

http://www.youtube.com/watch?v=PNH7_nDE6SQ&feature=related



Significant Digits in Calculations
-If you type in 7.7 meters by 5.4 meters to find the area of a floor in a calculator. The calculator would tell you 41.58 square meters which is four significant digits, but each measurement is two significant digits so the answer must only be displayed as 42, which is two significant digits.
- A calculated answer cannot be more precise than the least precise measurement from which it was calculated.
-Rounding - No decide how many significant figures to round to you must look at how many the two factors have. For example 62/41= 1.51219512 . Each 62 and 41 have two significant figures so you should round the answer to 1.5. Watch the videos they are very good.
-Addition and Subtraction - The number of decimal points should be the same as the number with the least. For example.
12.52 meters
349.0 meters
+ 8.24 meters
_
369.76 This answer needs to be rounded to one decimal digit, because that is how many 349.0 has. So the final answer is 369.8
-Multiplication and Division - The rule is the same here that you need to round your final answer to have the same number of decimal points as the value with the least decimal points.
7.55 meters X .34 meters = 2.567 Meters squared. = 2.6 meters squared because .34 as two significant figures


3.2 International System of Units
p. 73-75 Chris Hart

Measuring with SI Units

All measurements depend on units that serve as reference standards. The standards of measurement used in science are those of the metric system. The metric system is important because of its simplicity and ease of use. All metric units are based on multiples of 10, which allows for easy conversion between units. The International System of Units is a revised version of the metric system that was adopted by international agreement. There are seven SI base units. The five SI base units most commonly used are the meter, the kilogram, the kelvin, the second, and the mole.

SI Base Units

Quantity
SI base unit
Symbol
Length
meter
m
Mass
kilogram
kg
Temperature
kelvin
K
Time
second
s
Amount of substance
mole
mol
Luminous intensity
candela
cd
Electric current
ampere
A
Units and Quantities
Different quantities require different units. Before you make a measurement, you must be familiar with the units corresponding to the quantity that you are trying to measure.

Units of Length

In SI, the basic unit of length, or linear measure, is the meter (m). For very large and very small lengths, however, it may be more convenient to use a unit of length that has a prefix.

For example, the prefix milli- means 1/1000 (one-thousandth), so a millimeter (mm) is 1/1000 of a meter. A hyphen (-) measure about 1 mm. For large distances, it is usually most appropriate to express measurements in kilometers (km). The prefix kilo- means 1000, so 1 km equals 1000 m. A standard marathon distance race of about 42,000 m is more conveniently expressed as 42 km.

Common metric units of length include the centimeter, meter, and kilometer.

Units of Volume

The space occupied by any sample of matter is called its volume. You calculate the volume of any cubic or rectangular solid by multiplying its length by its width by its height. The SI unit of volume is derived from the meter and is the amount of space occupied by a cube that 1 cubic meter.

A more convenient unit of volume for everyday use is the liter, a non-SI unit. A liter (L) is the volume of a cube that is 10 centimeters along each edge. A smaller non-SI unit of volume is the millimeter; 1 mL is 1/1000 of a liter. The units milliliter and cubic centimeter are equal and thus used interchangeably.

Common metric units of volume include the liter, milliliter, cubic centimeter, and microliter.

There are many devices for measuring liquid volumes, including graduated cylinders, pipets, burets and syringes. The volume of any solid, liquid or gas will change with temperature. Accurate volume-measuring devices are calibrated at a give temperature-usually 20 degrees Celsius, which is about normal room temperature.

p. 76-79 Abbey Salvas

Units of Mass

The mass of an object is measured in comparison to 1 kg, the SI unit of mass. A gram is 1/1000 of a kilogram and the mass of 1 cm3 of water at 4 degrees Celsius. Common metric units of mass include the kilogram, gram, milligram, and microgram.

You can use a platform balance to measure mass. You place the object on one side of the balance and standard masses are placed on the other side until the sides of the balance are equal. The unknown mass is equal to the sum of the standard masses.

Weight is a force that measures the pull on a given mass by gravity. It is a measure of force, while mass is a measure of the quantity of matter. Weight can change with its location, while mass remains constant regardless of its location.

Units of Temperature

Temperature is a measure of how hot or cold an object is. An object's temperature determines the direction of heat transfer. When two objects at different temperatures are in contact, heat moves from the object at the higher temperature to the object at the lower temperature.

Almost all substances expand with an increase in temperature and contract as the temperature decreases, except water. This is why liquid is used in glass thermometers.

Scientists commonly use two equivalent units of temperature, the degree Celsius and the kelvin.Celsius uses two references: the boiling point and the freezing point. The freezing point is 0 degrees and the boiling point is 100 degrees. The distance between these points is divided into 100 equal intervals, degrees Celsius.

The other scale used is the Kelvin, or absolute, scale.On this scale, the freezing point is 273.15 kelvins (K) and the boiling point is 373.15 K. The degree sign is not used on the Kelvin scale. The change of one degree on the Celsius scale is equivalent to one kelvin on the Kelvin scale. 0 K is absolute zero and it is equal to -273.15 degrees Celsius. To convert to Celsius from Kelvin, use the formula: K=C+273. To convert from Celsius to Kelvin use the formula: C=K-273.

Units of Energy

Energy is the capacity to do work or to produce heat. The joule and the calorie are common units of energy. The joule (J) is the SI unit of energy. One calorie (cal) is the quantity of heat that raises the temperature of 1g of pure water by 1 degree Celsius.
1 J=0.2390 cal
1 cal=4.184 J


3.3 Conversion Problems
p. 80 Siri Devlin
A quantity can usually be expressed in several different ways.
For example, consider the monetary amount $1.
1 dollar= 4 quarters= 10 dimes= 20 nickels= 100 pennies
These are all expressions, or measurements, of the same amount of money. The same is true of specific quantities.

For example, consider a distance that measures exactly 1 meter.
1 meter= 10 decimeters= 100 centimeters= 1000 millimeters

Whenever two measurements are equivalent, a ratio of the two measurements will equal 1, or unity.
1m/1m = 100cm/1m
1 or 1cm/100cm
100cm/100cm = 1
(Blue fractions are Conversion Factors)
⌘ A conversion factor is a ratio of equivalent measurements.

In a conversion factor, the measurement in the numerator (on the top) is equivalent to the measurement in the denominator (on the bottom).
When a measurement is multiplied by a conversion factor, the numerical value is generally changed, but the actual size of the quantity measured remains the same.

p. 81 Brendan Morrissey
Dimensional Analysis
One of the best methods for solving any type of problem is dimensional analysis.
Dimensional Analysis is a way to analyze and solve problems using the units, or dimensions, of the measurements.
Example: How many seconds are in a workday that lasts exactly eight hours?

STEP ONE: ANALYZE
-List the knowns and the unknowns.**
-Knowns
  • time worked=8 hours
  • 1 hour=60 minutes
  • 1minute=60 seconds
-Unknowns
  • seconds worked=?s
-The first conversion factor must be written with the unit hours in the denominator. The second conversion factor must be written with the unit minutes in the denominator. This will provide the desired unit (seconds) in the answer.

STEP 2:CALCULATE
- Solve for the unknown.
-Start with the known, 8 hours. Use the first relationship (1 hour=60 minutes) to write a conversion factor that expresses 8 hours as minutes. The unit hours must be written in the denominator so that the known unit will cancel. Then use the second conversion factor to change the unit minutes into the unit seconds. This conversion factor must have the unit minutes in the denominator. The two conversion factors can be used in a simple overall calculation.
-8 h (cancelled) X 60 min (cancelled) /1 h (cancelled) X 60 s (cancelled) / 1 minute (cancelled) =28,800 seconds = 2.8800 X 10^4 seconds

STEP THREE: EVALUATE
-Does the result make sense?
-The answer has the desired unit (seconds). Since the second is a small unit of time, you should expect a large number of seconds in 8 hours. -Before you do the actual arithmetic, it is a good idea that the units cancel and that the numerator and the denominator are equal to each other. The answer is exact since the given measurementand each of the conversion factors is exact.


There is usually more than one way to solve a problem. Some problems are easily worked with simple algebra.
Dimensional Analysis provides you with an alternative approach to problem solving.

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p. 84 Phillip Royal

Converting Between Units

- Problems concerning conversion between units can easily be resolved by using dimensional analysis
- A laboratory experiment requires 7.5 dg of magnesium and 100 students are doing the experiment
- Question: How many grams of magnesium should the teacher have on hand?

STEP ONE: ANALYZE
- List was is known and unknown
-mass = 750 dg - 1 gram = 10 decigrams - mass = ? grams

STEP TWO: CALCULATE
- You than find the conversion factor
- In this problem it is 1 gram / 10 decigrams*
- Than multiply the known by the conversion factor to find the outcome Known unit is in he denominator and the unknown is in the numerator 750 dg x 1g / 10dg = 75 g

STEP THREE: EVALUATE
Does it make sense?
- In this case it does
- The number of grams is smaller than the number of decigrams, and grams is a large measure than decigrams
- Thus the conclusion is reasonable Multistep Problems
- Many complex word problems are solved by breaking the solution into multiple steps
- It is often necessary to use more than on conversion factor Question: What is 0.073 cm in micrometers?


STEP ONE: ANALYZE
- Known:
-Length = 0.073 cm = 7.3 x 10^-2cm - 10^2 cm = 1 m - 1 m = 10^6 μm
- The problem can be solved in a two step conversion

STEP TWO: CALCULATE

- First we change cenimeters to meters and than meters to micrometers
- Each conversion factor shall be written so that the denominator cancel the unit in the numerator of the previous factor
-7.3 x 10^-2 cm x 1m / 10^2 cm x 10^6 μm / 1 m = 7.3 10^2 μm

STEP THREE: EVALUATE
- Yes, the answer makes sense
- Micrometers are a much smaller measure than centimeters. Thus it makes sense that the answer is a very large number when converted from cm to mm



3.4 Density
p. 89-90 Ben Ross

p. 91-93 Kerry Desmond
Density and Temperature
-density is the ratio of the object's mass to its volume.
-Volume changes with temperature; therefore, density changes with temperature.
-The density of a substance generally decreases as its temperature increases
-an important exception is water.

You can use dimensional analysis to calculate density:
-A copper penny has a mass of 3.1 g and a volume of .35 cm cubed. What is the density of copper?
-the destination is to find out what the density of copper is.
-Let's start by finding out what we know:
The mass of the coin is 3.1 grams.
The volume of the coin in .35 centimeters cubed.
-All that's left is to plug the values into the formula.
Density= Mass/Volume
3.1 g / 0.35 cm cubed= 8.8571 g/ cm cubed.
-Remember, you have to round to a significant figure, so the answer would be 8.9 g/ cm cubed.

You can also use density to calculate volume.
-What is the volume of a pure silver coin that has a mass of 14 g? The density of silver is 10.5 g/ cm cubed.
-Our destination is to find the volume of the coin.
-Let's look at what we know:
Mass of coin= 14 g
density of silver= 10.5 g / cm cubed.
-Let's use what we know to solve the problem.
14 g x 1 cm cubed= 14 g/cm cubed
14 g/ cm cubed divided by 10.5 g= 1.3 cm cubed silver.**




Misc.