CHAPTERS 1 AND 3, PERIOD F

editor- Kayla Anghinetti
LINKS AND VOCAB
http://chemistry.about.com/od/chemistry101/a/basics.htmhttp://www.chemistry.co.nz/what_is_chemistry.htm
- What is Chemistry? Thorough definitions of chemistry, physical chem., analytical chem., etc.
http://www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/scientist.html
- Cute story thing about the scientific method... I guess it’s funny if you like educational things.
http://www.cleavebooks.co.uk/dictunit/
- Dictionary of units; summary of units of measurements used today, with conversion factors needed to change them into standard units.
http://chemistry.about.com/od/chemistryquickreview/a/accuracyprecise.htm
- Review of accuracy and precision
http://www.factmonster.com/ipka/A0001658.html
- Quick summary of the International System of Units (Metric)
http://www.csudh.edu/oliver/chemdata/convfact.htm
- Table of common conversion factors.
http://www.chemistrydaily.com/chemistry/Density
- Density in-depth


CHAPTER 1 VOCAB:
Analytical chemistry - focuses on the composition of matter
Applied chemistry - research directed toward a practical goal or application
Biochemistry - focuses on processes that take place in organisms
Biotechnology - field that applies science to the production of biological products/processes
Chemistry - study of the composition of matter and the changes in undergoes
.Experiment - repeatable procedure that is used to test a hypothesis
Hypothesis - proposed explanation for an observation
Inorganic Chemistry - study of substances that, in general, don't contain carbon
Macroscopic - large enough to see with unaided eye Matter - anything that has mass and takes up space
Microscopic - can only be seen under a microscope
Manipulated variable - variable that is changed during an experiment (independent variable)
Observation - information obtained through senses
Organic chemistry - study of compounds containing carbon
Physical chemistry - deals with the mechanism, rate, and energy transfer that occurs when matter undergoes change
Pollutant - material found in air, water or soil that is harmful to humans or other organisms
Pure chemistry - pursuit of chemical knowledge for its own sake
Responding variable - variable observes during an experiment (dependent variable)
Scientific law - concise statement, summarizes results of many observations and experiments
Scientific method - logical, systematic approach to the solution of a scientific problem
Technology- means by which society provides members with those things needed and desired
Theory - well-tested explanation for a broad set of observations.


CHAPTER 3 VOCAB
Absolute zero - the zero point on the Kelvin temperature scale
Accepted value - value used for a substance's properties, accepted by everyone
Accuracy - correctness of a single measurement
Calorie (cal) - quantity of heat needed to raise temperature of 1g of pure water 1 degree Celsius
Celsius scale - freezing point is 0 degrees boiling point is 100 degrees.
Conversion factor - numerical factor used to multiply or divide a quantity when converting from system of units to another
Density - ratio of mass of an object to its volume
Dimensional analysis - technique of problem solving that uses the units that are part of a measurement to help solve the problem
Energy - capacity for doing work, forms= chemical, nuclear, electrical, radiant, mechanical and thermal.
Error - difference between accepted value and experimental value
Experimental value - quantitative value measured during experiment
Gram (g) - metric unit of weight equal to one thousandth of a kilogram
International System of Units (SI) - revised version of the metric system
Joule (J) - the SI unit of energy
Kelvin scale - temperature scale, freezing point is 273k, boiling point is 373k, 0k is absolute zero
Kilogram (kg) - the mass of 1L of water at 4 degrees C, base unit of mass in SI
Liter (L) - volume of a cube measuring 10 cm on each edge; common unit of volume in the metric system
Measurement - process of estimating or determining the magnitude of a quantity
Meter (m) - base unit of length in SI
Percent error - percent that a measured value differs from the accepted value
Precision - measure of how close a series of measurements are to one another
Scientific notation - method of writing or displaying numbers in terms of a decimal number between 1 and 10 multiplies by a power of 10
Significant figures - includes all known digits, plus a last digit that is estimated
Temperature - measure of the average kinetic energy of particles in matter
Weight - force that measures the pull of gravity on a given mass.


GROUP 1

Co-editor: Shannon Leavey Group Members: Lindsey Chou & Shannon Leavey

What is Chemistry?
-Matter: is anything that has mass and occupies space
Ex: the color pigments in leaves that change the colors from greens to orange and yellow in the fall.
-Chemistry: the study of the composition of matter and the changes that matter undergoes.
*because living and non living things are made of matter, chemistry affects aspects of life and most natural events*
Why Study Chemistry?
*Chemistry can be useful in explaining the natural world, preparing people for career opportunities, and producing informed citizens

Explaining the natural world
-chemistry explains how things work
-example: it explains why apples turn brown

Preparing for a career
-fire fighters need to know about chemistry in order to know how to fight fires
-reporters may be doing a story on chemistry, so they will need to know basic facts

Being an Informed Citizen
-you need it in order to vote
-we need things we find in space like smoke detectors, heart monitors, and television
-knowledge of sciences can help us evaluate the data presented to

Chapter 1.1 Outline – What is Chemistry? Part 2 (pgs. 8 – 9) By Lindsey Chou
5 Traditional Areas of Study:
o Organic chemistry – the study of all chemicals containing carbon
o Inorganic chemistry – the study of chemicals that, in general, do not contain carbon
o Biochemistry – the study of processes that take place in organisms
o Analytical chemistry – the area of study that focuses on the composition of matter
o Physical chemistry – the area that deals with the mechanism, the rate and the energy transfer that occurs when matter undergoes a change
The boundaries between these five areas aren’t firm, so chemists will most likely work in more than one area of chemistry at a time.

Pure and Applied Chemistry:
o Pure chemistry – the pursuit of chemical knowledge for its own sake
o Applied chemistry – research that is directed toward a practical goal or application
Pure research can lead directly to an application, but an application can exist before research is done to explain how it works, two examples are aspirin and nylon.
o Nylon – A German chemist named Hermann Staudinger proposed that materials like cotton and silk are made of small units that link together in a chain. Wallace Carothers tested this proposal, and the research was eventually applied in the form of nylon production.
o Aspirin – Aspirin was used for pain relief before it was totally understood. In 1971 it was found to be useful for stopping blood clots.
These are examples of technology = something that allows humans to do things more quickly or with less effort


GROUP 2

Co-editor:Teresa Lynch; Group Members: Elena Conroy & Teresa Lynch

1.2: Chemistry Far and Wide ( pg. 12-19)
Materials
* Chemists design materials to fit specific needs
-George de Mestral studied burrs from the woods
- ^ resulted in the production of hook-and-loop tapes
*Two ways of looking at the world
 -macroscopic-> world of objects that are large enough to see with the unaided eye
-microscopic-> world of objects that can be seen only under magnification
Energy
 - high in demand, used often in modern society today
-Chemists play an essential role in finding ways to conserve energy, produce energy, and store energy
-Conservation-> easiest way is through the use of insulation
-Production-> looking for fuels other than fossil fuels that can be made into energy
-Storage-> study batteries that can be re-charged
Medicine and Biotechnology
*Chemistry supplies the medicines, materials, and technology that doctors used to treat their patients
-the goal is to understand matter in the human body and chemical changes that occur in cells
-Medicines: -designed to interact a specific way with chemicals in cells -chemists design safe and effective drugs
-Materials: -chemists design materials to help repair or replace body parts: -plastic "skin" -artificial hips and knees
-Biotechnology: -applies science to the production of biological products or processes: -is able to alter DNA and change genes of DNA
Agriculture
*Chemists help to develop more productive crops and safer, more effective ways to protect crops
-Productivity: -chemist fight problems that cause lack of productivity, or the amount of edible food that is grown on a given unit of land
-Crop Production: -now design pest killers to target certain insects -sometimes used chemicals produced by insects to fight insects
The Environment
*Consequence of new technologies:
pollutant - materials found in air, water, or soil that is harmful to humans or other organisms: -Chemists help to identify pollutants and prevent pollution
*Identify Pollutants: -Lead is a pollutant: it was used throughout history until it was tested and found to be a pollutant
*Prevent Pollution: -Lead was banned from paint and then gas and water -Still located in lead-paint in older houses; however there are rules and regulations now to make sure that lead never enters people's blood streams
The Universe
To study the universe, chemists gather data from afar and analyze matter that is brought back to Earth.
-Pierre Janssen discovered a gas on the sun: helium ("helios" or "sun" Greek) -William Ramsay discovered helium on Earth. -Scientists depend on matter brought back to Earth by astronauts or probes


GROUP 3

Co-editor: Neal McGovern; Group Members: Bryan Dextradeur and Neal McGovern


1.3 Thinking like a Scientist

BY: Bryan Dextradeur

Alchemy

  • The word "Chemistry" comes from the word "Alchemy".
  • Alchemy was the study of matter that was practiced in the world long before chemistry, as early as 400 B.C.
  • Alchemy has two sides: Practical and Mystical.
    1. The Practical Side of Alchemy focused on developing techniques for working with metals, glass, and dyes.
    2. The Mystical Side of Alchemy focused on concepts like perfection; this is because the scientists viewed gold as the perfect substance and were trying to develop ways to change other materials into gold.
  • Alchemy led to Chemistry.

· Alchemy developed the tools and techniques for working with chemicals.

o Alchemists developed processes for separating mixtures and purifying chemicals.
o Alchemists designed equipment that is still used today, including beakers, flasks, tongs, funnels, and the mortar and pestle.
o Alchemists did not, however, produce explanations to account for the changes in matter they observed.

An Experimental Approach to Science

  • By the 1500's in Europe, there was a shift from Alchemy to Science.
  • Science thrived in Britain in the 1600's because of support form King Charles II.
  • Many Scientists formed a group called the Royal Society of London for the Promotion of Natural Knowledge, a group that sought to base conclusions about the natural world on experimental evidence instead of ideas of Philosophy.

· Lavoisier helped to transform Chemistry from a science of observation to the science of measurement that it is today.

    • Antoine Lavoisier worked during the 1700's in France.
    • He developed a balance that could measure mass to the nearest 0.0005 gram.
    • Lavoisier is well known for settling an endless debate about how materials burn.
      • The accepted explanation at the time was that materials burn because they contain phlogiston, which is released into they air as they burn.
      • Scientists ignored evidence that metals can gain mass as they burn.
      • Lavoisier knew that the air contained nitrogen and oxygen and proved that oxygen is required for a material to burn.
  • Lavoisier was beheaded during the French Revolution because of his role in the taxation commission.

The Scientific Method

  • The Scientific Method is a logical, systematic approach to the solution of a scientific problem.
  • Steps in the Scientific Method include making observations, testing hypotheses, and developing theories.

Making Observations

  • An Observation is when you use your senses to obtain information.
  • Closely related to common sense.
    • Example: You try to turn on your car but you observe that it will not start; this may lead you to question why it will not start.

Testing Hypotheses

  • A Hypothesis is a proposed explanation for an observation.
    • Example: You hypothesize that your car may be out of gas. You can test this hypothesis by putting gas into your car and testing to see if it will start. If it does start, your hypothesis is probably true, but if it still does not start, you have to come up with a new hypothesis, perhaps that the car is out of oil, and test that hypothesis.
  • An Experiment is a procedure that is used to test a hypothesis.
    • Example: Testing to see if your car runs after refilling it with gas.
  • Variables are factors in an experiment that change.
  • The Manipulated Variable, or Independent Variable, is the variable that is changed during an experiment.
    • Example: In the car scenario, the gas is the manipulated variable because it is what is being changed.
  • The Responding Variable, or Dependent Variable, is the variable that is being observed during an experiment.
    • Example: In the car scenario, the car is the responding variable because it is what is being observed.
  • All other variables in an experiment must stay the same in order to ensure that the independent variable caused any changes that may have occured.
  • In order for an experiment to be accepted, it must produce the same results no matter how many times it is performed.
BY: Bryan Dextradeur
Chapter 1.3
Thinking Like a Scientist
Part 2, pages 23-25
By Neal McGovern (co-editor)
Developing Theories
· Once a hypothesis is proved, it can be raised up a notch to a theory
· A theory is a well-tested explanation for a broad set of experiments
· A theory is not provable, but that does not mean that it is unreliable
Scientific Laws
· Experiments can not only lead to theories, but laws as well
· A scientific law is a concise statement that summarizes the results of many experiments
· Laws describe the results of the experiments, while theories try to explain them
Collaboration
· To collaborate is to work together
· Occasionally, scientists will collaborate to solve extremely difficult and complex research problems
· They do this so they will have maximum knowledge of all of the fields of science they will need to know to answer the research question
· Another reson may be that one side of the collaborators has better equipment for the job, but the other side has better knowledge and personnel than the other side
· Collaboration is often a bumpy road, for issues will arise about credit, amount of work, and uses of resources, but it usually has good results
Communication
· Communication between scientists has changed over the centuries
· The way they have communicated has gone from letters to published jounals to e-mail
· The scientific journals are still the most reliable source of information about new discoveries that you can get
· The Internet is the biggest source of information
· The advantages of the Internet is that anyone can have access to its information
· On the flipside of that is that anyone can post on it without the info being reviewed
· To judge if the info is reliable, you must consider the source; if it came from a prominent scientist's website, then it is probably reliable


GROUP 4
Co-editor: Emily Stewart
Group Members: Emily Stewart and Hannah Kumlin
Effective problem solving requires developing and following a plan.
You might refer to a data table, a graph, or another type of visual when solving a problem.

Solving Numeric Problems:

You are visiting Indianapolis for the first time. Because it is a nice day, you decide to walk from the Indiana State Capital to the Murat Centre for an afternoon performance. The shortest route from the capital to the theater is 8 blocks. How many minutes will the trip take if you can walk one mile in 20 minutes? Assume that 10 short city blocks equals 1 mile.

Analyze
What do you know?
Distance to be traveled = 8 miles
Walking speed = 1 mile/20 minutes
1 mile = 10 blocks
What do you need to find out?
Time of trip……. How many minutes?

Calculate
8 blocks × 1 mile = .8 mile
10 blocks

0.8 miles × 20 minutes = 16 minutes
1 mile

Evaluate
Does the answer make sense?
Yes – 16 minutes to walk 8 short blocks
Chapter 1.4


Problem Solving in Chemistry

(part 2 pgs 30-32)

By: Hannah Kumlin (Group Helper Person)

Solving Conceptual Problems

· Not every word problem in chemistry requires calculations - some ask you to apply concepts you are studying to a new situation.

· These problems are called conceptual problems.

- To solve one, you still have to identify what is known and what is unknown and make a plan to get from the known to the unknown.

- If your answer is not a number, you don't need to check the units, make an estimate, or check calculations.

· The steps for solving conceptual problems are:

1. Analyze- Figure out what the problem tells you and what is unknown and organize the information.

2. Solve- Using the information, find the answer to the problem.

Numeric Word Problem Example:

You are visiting Indianapolis for the first time. Because it is a nice day, you decide to walk from the Indiana State Capital to the Murat Centre for an afternoon performance. The shortest route from the capital to the theater is 8 blocks. How many minutes will the trip take if you can walk one mile in 20 minutes? Assume that 10 short city blocks equals 1 mile.


1. Analyze:

What we know:
-Distance to be traveled = 8 blocks
-Walking speed = 1 mile/20 minutes
-1 mile = 10 blocks

What we don't know:
-time of trip = ? minutes

2. Calculate:
Divide the distance to be traveled (in blocks) by the number of blocks in one mile to get the distance of the trip in miles. Then multiply the number of miles by the time it takes to walk one mile.
3. Evaluate:It takes 16 minutes to walk 8 short blocks.



Conceptional Problem Example:

Manny has to run 6 errands between 10 and 5 on Saturday. He must get a haircut, wash his car, buy stamps, rent a video, return a library book, and buy some groceries. Assume that each errand will take 30 minutes and that Manny will do only one errand per hour. Manny will stop for a lunch break between 12 and 1. Use the information in the drawing to figure out a way for Manny to acomplish all 6 tasks.
(refer to page 32 in textbook for the picture)


1.Analyze:

Each place that Manny needs to visit is open for a limited number of hours on Sat. Manny must do his errands between 10 and 12, and between 1 and 5. At a rate of one errand per hour, Manny must do 2 errands before lunch and 4 errands after lunch.


2.Solve:

The post office and library are open only in the morning. The barbershop and the car wash close earlier than the video store. The supermarket is open late. One possible order for the errands is post office, library, barbershop, car wash, video store, and supermarket.


GROUP 5
Co-editor – Nikki Sheehan
Nikki Sheehan and Chris Kelly

Measurements and Their Uncertainty
Using and Expressing Measurements - A measurement is a quantity that has both a number and a unit
-“Measurements are fundamental to the experimental sciences.
For that reason, it is important to be able to make measurements and to decide whether a measurement is correct.”
-Large numbers are often used in chemistry; but to make writing these numbers simpler, we can use scientific notation -in scientific notation, a given number is written as the product of two numbers
-a coefficient and 10 raised to a power Ex. 602,000,000 can be written as 6.02 x 10^8 -the coefficient is always a number equal to or greater than one and less than 10, in scientific notation
-the power of 10 (exponent) is the number of places to the left or right the decimal point is moved Accuracy, Precision, and Error
-measurements should be correct and reproducible Accuracy and Precision -accuracy is the measure of how close a measurement comes to the actual or true value of whatever is measured -precision is a measure of how close a series of measurements are to one another
-“To evaluate the accuracy of a measurement, the measured value must be compared to the correct value. To evaluate the precision of a measurement, you must compare the values of two or more repeated measurements.”
A. The darts land far apart and far from the bulls eye. They are neither accurate nor precise.
B. The darts land close together but far from the bulls eye. They are precise but not accurate.
C. The darts land close to the bulls eye but far apart. They are accurate but not precise.
D. The darts land close together and close to the bulls eye. They are accurate and precise.

Determining Error -measurements may be accurate or inaccurate
-accepted value is the correct value based on reliable references
-experimental value is the value measured in the lab
-the two values may not always be exactly the same
-error is the difference between the experimental value and the accepted value
Ex. error = experimental value – accepted value
-it is often useful to calculate percent error (relative error)
Ex. percent error = |error| / accepted value x 100%
-just because a measuring device works, doesn't necessarily mean that it is accurate
-make sure a measuring device is zeroed before using it



GROUP 6
Co-editor: Lauren Murphy
Group Members: Lauren Murphy and Ellie Kawa
Metric Units of Mass
Unit
Relationship
Kilogram (kg) (base unit)
1kg=10³g
Gram (g)
1g=10-³kg
Milligram (mg)
10³mg=1g
Microgram (µg)
10^6 µg=1g

Ellie Kawa pgs 76-79

Units of Mass

· the mass of an object is measured in comparison to a standard mass of 1 kilogram (kg), the basic SI unit of mass
o kilogram- the mass of 1 L of liquid water at 4°C

gram (g)
- 1/1000 of a kilogram; the mass of 1 cm³water at 4°C is 1 g

common metric units of mass
- kilogram, gram, milligram, and microgram
· the platform balance can be used to measure the mass of an object
o object is placed on one side of the balance, and standard masses are added to the other side until the balance beam is level
o unknown mass is equal to the sum of the standard masses
· analytical balance- used to measure objects of less than 100 g and can determine mass to the nearest 0.0001 g (0.1 mg)


Weight-
a force that measures the pull on a given mass by gravity
o mass remains constant regardless of its location- objects can become weightless, but can never become massless

Units of Temperature

Temperature-
a measure of how hot or cold an object is
o determines the direction of heat transfer
o 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
o almost all substances expand with an increase in temperature and contract as the temperature decreases


Scientists commonly use two equivalent units of temperature, the degree Celsius and the Kelvin
o Celsius scale- named after Swedish astronomer Anders Celsius
o freezing point: 0°C, boiling point: 100°C
o Kelvin, or absolute, scale- named after Lord Kelvin, a Scottish physicist and mathematician
o freezing point: 273.15 kelvins, boiling point: 373.15 kelvins
§ a change in one degree on the Celsius scale is equivalent to one Kelvin on the Kelvin scale

absolute zero-
the zero point on the Kelvin scale equal, 0 K, equal to -273.15°C

Units of Energy

Energy
- the capacity to do work or to produce heat

the joule and the calorie are common units of energy

joule (j)-
SI unit of energy, named after English physicist James Prescott Joule

calorie (cal)-
one calorie is the quantity of heat that raises the temperature of 1 g of pure water by 1°C


3. 2 The International System of Units By: Lauren Murphy (p. 73-75)

Measuring with SI Units:
· -All measurements depend on the unit used
· -All metric units are based on multiples of ten
· -International System of Units (SI) is the revised version
· -7 SI base units
· -5 units used by chemists are meter, kilogram, kelvin, second, mole

Units and Quantities:
· -Size is an important property of matter
· -Basic SI unit of length = meter
· -For smaller or larger distances, prefixes are used·
-Common metric units of length include the centimeter, meter, and kilometer
-Space occupied by matter is called volume
· -Volume= length x width
· -Liter, a non-SI unit is easy to use
· -Common metric units of volume include liter, milliliter, cubic centimeter, and microliter
· -Many devices for measuring liquid volume: graduated cylinder, pipets, burets, volumetric flasks, syringes
-Volume of any liquid, solid, or gas will change with temperature · -International System of Units (SI) is the revised version
· -7 SI base units
· -5 units used by chemists are meter, kilogram, kelvin, second, mole

Units and Quantities:
· -Size is an important property of matter
· -Basic SI unit of length = meter
· -For smaller or larger distances, prefixes are used·
-Common metric units of length include the centimeter, meter, and kilometer
-Space occupied by matter is called volume
· -Volume= length x width
· -Liter, a non-SI unit is easy to use
· -Common metric units of volume include liter, milliliter, cubic centimeter, and microliter
· -Many devices for measuring liquid volume: graduated cylinder, pipets, burets, volumetric flasks, syringes
-Volume of any liquid, solid, or gas will change with temperature

GROUP 7 David Monti (co-editor) & Jessen Foster, Conversion Problems, p.80-88

Converting Between Units

- Problems in which a measurement with one unit is converted to an equivalent measurement with another unit are easily solved using diemntsional analysis

SAMPLE: Express 750 decigrams in grams.

1. Analyze: List knowns and the unknown

 Known Unknown

 - mass = 750 dg - mass = ? g

- 1 g = 10 dg

2. Calculate: Solve for unknown

1 gram <---unknown

10 dg <---known

750 dg X 1 gram

10 dg...

desired conversion: g/cm^3 to kg/m^3

-numerator: g to kg

-denominator: cm^3 to m^3

2. Calculate: Solve for unknown

7.21g X 1 kg X 10^6 cm^3 = 7.21 (1) (10^6) kg = 7.21 X 10^3 kg/m^3

1cm^3 10^3 g 1 m^3 (1) (10^3) (1) m^3

3. Evaluate: Does your result make sense?

-physical size of volume unit m^3 is larger than cm^3 (10^6 times) so the density should be larger

-mass unit is 10^3 times larger

By David Monti, Co-editor

Conversion Factors
- Quantities can be expressed in several ways
1. 1dollar
2. 4 quarters
3. 10 dimes
4. 20 nickels
5. 100 pennies
- Whenever two measurements are equivalent, a ratio of the two measurements will equal 1, or unity
ex. 1m 100 cm 1m = 1m = 1
- Conversion Factor is a ratio of equivalent measurements
ex. (100cm/1m and 1m/100cm)
- The measurement in the numerator must always equal the measurement in the denominator
- The larger number is part of the measurement with the smaller unit
- When a measurement is multiplied by a conversion factor, the numerical value is generally changed, but the actual size of the quality measured remains the same ·
Ex. Even though 1g and 10 dg differ, they both represent the same value, or mass. ·
Ex. 1000g = 1kg. conversion factors are 1000g/1kg and 1kg/1000g

Dimensional Analysis
- Dimensional Analysis is a way to analyze and solve problems using the units, or dimensions, of the measurements - It is broken up into a simple 5 step process
1. Identify the destination including units
2. Choose a starting point (Given)
3. List the connecting conversion factors
4. Multiply starting measurement by conversion factors
5. Does the answer make sense?
- Dimensional analysis provides you with an alternative approach to problem solving
Example #1
How many seconds are there in a workday that lasts exactly eight hours? Seconds = 8 hours X 60 min X 60 s = 8X60X60 = 28,800 Seconds 1 h 1 min Example #2
The directions for an experiment ask each student to measure 1.84 g of copper (Cu) wire. The only copper wire available is a spool with a mass of 50.0 g. How many students can do the experiment before the copper runs out? Students = 50 g X 1 student = 50 = 27 students 1 Spool 1.84 g 1.84

TIP: Always start with the destination = the given. When you reach the unit for the destination again. You have reached the end

GROUP 8

Coeditor: Kayla Anghinetti DENSITY, 3.4 I. Determining Density A. Density is the ratio of an object's mass to its volume. B. When mass is measured in grams, and volume in cubic centimeters, density has units of grams per cubic centimeter. (G/cm3) C. Volumes vary because substances have different densities D. Density is an intensive property that depends only on the composition of a substance, not on the size of the sample II. Density and Temperature A. Often, volume of most substances increases with temperature a. Mass remains the same despite temperature and volume changes. b. If volume changes with temperature, then density must also change. c. The density of a substance generally decreases as temperature increases. EXAMPLE PROBLEMS (p. 91 and 92) CALCULATING DENSITY A copper penny has a mass of 3.1g and a volume of 0.35cm3. What is the density of copper? 1. Analyze; list the knowns and the unknown.

Known: Unknown Mass

3.1g Density = ? G/cm3 Volume = .35cm3 2. Calculate; solve for the unknown. a. Substitute the known values, and calculate. 3. Evaluate; does the result make sense? Does an estimate you can make agree with the calculated result? Does the number make sense? USING DENSITY TO CALCULATE VOLUME What is the volume of a pure silver coin that has a mass of 14g? The density of silver is 10.5G/cm3. 1. Analyze; list the knowns and the unknown. Known: Unknown Mass = 14g Volume = ?cm3 Density = 10.5G/cm3 In this problem, Density can be used as a conversion factor. 2. Calculate; solve for the unknown. a. Multiply the mass of the coin by the conversion factor. 3. Evaluate; does the result make sense? It makes sense that 14.g of silver has a volume slightly larger than 1cm3 because a mass of 10.5 g has a volume of 1cm=