The Central Science Chemistry is called “The Central Science” because it overlaps so many sciences.

Why Should YOU Study Chemistry?
Chemistry is everywhere and in everything Chemistry gives you a better understanding of the world. “There is a sucker born every minute” –PT Barnum You don’t want to be that person Chemistry is fun. No, really! Pop rocks, fireworks, lava lamps, everything you eat, how things cook, and many toys are based on chemical principals that we’ll cover this year

What is the Chemistry. What are the sub-fields in Chemistry
What is the Chemistry? What are the sub-fields in Chemistry? How does it fit into “science” as a whole?

Classification of the sciences
One way to classify the sciences is to divide them into three basic types: Physical sciences Life sciences Social sciences

Classification of the sciences
Physical sciences attempt to explain natural non-living objects and phenomena Chemistry, physics, geology, and astronomy Life sciences deal with living things Biology and medicine Social sciences deal with human behavior and civilization Economics, anthropology, sociology, psychiatry, even education

Chemistry is the study of substances and the changes they undergo.
Chemistry Chemistry is the study of substances and the changes they undergo. Anywhere on Earth or in stars Any change Physical, chemical, or nuclear

Six Major Divisions of Chemistry
Organic Chemistry Carbon-based chemistry Fuels, plastics, synthetic fabrics, varnishes and coatings Applies to biochemistry and environmental chemistry Biochemistry Chemistry The Chemistry of Life Animal and plant sciences; genetics, medicine

Six Major Divisions of Chemistry, cont’d
Physical Chemistry Related to the physical principles behind chemical behavior Heat, work, energy, atomic structure and behavior Inorganic Chemistry The chemistry of all elements other than carbon Mining, metal work (steel, titanium, aluminum, alloys), semiconductors and silicon- based chips

Six Major Divisions of Chemistry, cont’d
Analytical Chemistry The science behind determining the amounts of materials in samples Water testing, drug tests, quality assurance, manufacturing facilities Environmental Chemistry Apply chemical principles to the study of the environment Soil testing, determining the amounts and effects of pesticides, monitor pollution

But can also include subsets:
Nuclear (Physical) Polymer (Organic) Materials (Inorganic, but can also be organic) Thermochemistry (Physical) Pharmaceutical (Biochemistry) Medicinal (Biochemistry) Geochemistry (Environmental, Organic, Inorganic combo) Astrochemistry (Physical) Crystallography (Physical, Analytical) Nanotechnology (Organic, Physical, Analytical) Forensics (Analytical, Organic, Inorganic, Biochemistry, Physical)

Chemistry the Science What all of the sciences have in common is that they use scientific methods. What is are scientific methods? Are they the same as the scientific method we have learned since grade school? What all, exactly, are we talking about here?

How Do We Gain Knowledge?
How do humans learn new things? Two basic methods: Revelation Experimentation

Somebody gives us the information (it is revealed to us).
Revelation Somebody gives us the information (it is revealed to us). Believe or disbelieve information based on our opinion of the validity of the source. Very common. Examples: College Lecture Course A Religion’s “Sacred Text”

We gather the information ourselves. Believe or disbelieve
Experimentation We gather the information ourselves. Believe or disbelieve based on our opinion of the validity of the data. Examples: Scientific methods Comparison Shopping

Examples Let’s consider a hypothetical situation: You are young. You are exploring your house and you have become interested in the burners on the stove. You want to know how they feel.

The first way to answer the question
Mom or Dad notices you near the stove; they give you a warning… “Careful! Hot!” Revelation: warning from parent. Information gained: the object is hot. Touching it will hurt. Possible conclusions: Mom/Dad is wrong (invalid source); go ahead and touch. Mom/Dad is right; don’t touch.

The second way: Experimentation
No parent is near by, so you reach out and touch the burner yourself. Experimentation: You touch the hot object yourself. Information gained: Object is hot. Touching it hurt. Conclusions: Data are valid – object is hot. Don’t touch again!

The Basic Idea… When you find out something by learning it from someone else, that’s revelation. When you find out something by figuring it out for yourself, that’s experimentation, or using Scientific Methods

Burner alternative: Maybe the burner was not on and it was not hot at that time, and you now think it is fine. However, it is possible that at some point in the future, you get burned when you touch it. The point is, you can modify your beliefs after learning something new, and specifically after experimentation. That’s what all the arrows are about. Scientists retest and modify all the time It’s their job How they do it….

The “Scientific Method”
Stop and think about how many steps there are in the scientific method that you have been taught

One possible set

Ummmmm…. There is no one “Scientific Method” that is a required list of steps all scientists follow sequentially. In fact, many scientists go back and forth between steps many times It’s why there are so many arrows However, there are patterns to the behavior of scientists that are what we can collectively call “Scientific Methods”.

“Scientific Methods” Generally agreed upon are: Observation
Formation of a hypothesis Data collection via an experiment Forming conclusions All other pieces usually fit in to one of those four categories

Revision, revision, revision….
Jumping between steps happens However, you can’t have a conclusion before you experiment You can, however, do things like modify your hypothesis mid-experiment Make new questions Make changes to the experiment to answer new questions the next time around

A Good Summary:

Observation Facts about what you: See Smell Hear Taste Feel
Without adding any thoughts on the matter (like “it smells fabulous”; that would be an opinion, not a fact Ex: Cooking bacon

Observations are made Without adding any thoughts on the matter, such as “it smells fabulous….”, Or “Baconaise?! For real- for real?! That is awesome!” “Kevin Bacon is old.” “That old dead guy should not be wearing that hat.” These things are all opinions. Yes- opinions ARE important in science. But not during observation.

Observation Facts about what you: See: color change from red to brown
Smell: like bacon Hear: like sizzling Taste: like bacon Feel: like it goes from slimy to crispy

Hypothesis A statement that explains the observation
Most are phrased as “If….then…” statements, but they do not need to be If I cook the bacon a shorter amount of time, then it will not taste burnt Alternative, not as an “If… then…” : Reducing cooking time will result in better bacon

Control Experiment Make several batches of bacon, cooking each batch a different amount of time Relates back to the hypothesis This is not a coincidence The experiment must test the hypothesis

Controls and Variables
Controls stay the same The pan/ griddle The heat setting Type / brand of bacon Variables change only one should be controlled for at a time here, the cooking time

Independent Variables
What you set/ measure in the experiment It is the cause of the change In this case, it is the cooking time

The Dependent Variable
Is the outcome/ response that is measured Responds to the independent variable Named so because it depends on the independent variable It is the consequence of the independent variable In this case, the degree of doneness of the bacon

Side note on experimentation
Not all experiments are performed as control experiments with a independent variable assigned at certain intervals Experiments can also be observational Ex: following the health of two cohorts (smokers and non-smokers) for 20 years to determine the impact of smoking on lung health. What would be the dependent variable here? Lung health

What are the benefits of this type of study?
The drawbacks? Do you think that they are often used in Chemistry? If so, which field?

What are the benefits of this type of study?
Studies can be long term (decades) Can collect a large amount of data in a brief period Can do studies for groups that would not be ethical to assign (smoking) Studies are in natural setting Can include lots of variables

The Drawbacks? There can be error when people self report (under-report the number of cigarettes smoked) People may move in and out of groups (ex- smokers quit) Variables can act as confounders (you think you are testing one thing, but really you were testing something unnoticed)

Do you think that they are often used in Chemistry? If so, which field?
All of them! Medical tests involve analytical, biochemistry, and organic chemistry Drug trials Plastics degrading and having endocrine effects (BPA) Environmental studies can involve analytical, inorganic, biochemistry, organic and environmental chemistry Pesticides such as DDT Effects on mining on an area

After the experiment: Reporting
How scientists report data is not a step of the scientific method, although many scientists do report their findings in professional journals.

Formal reports typically include:
Title Results Abstract Data Observations on the experiment Introduction Background Purpose calculations Hypothesis Discussion Experimental Methods Error analysis Conclusion Materials See your CRH for more details on each; there is a lot of information there! Procedure

Data vs. Results Data Results: Is usually listed in a table or a chart
Does not include calculations Is not an explanation of what happened Results: Include calculations of raw data Graphs that show relationships between data line graphs Explain the data

Using Data Tables in Science
Data tables display data in an easy to read format You can quickly locate and see desired information, rather than read it, which is usually included in brief

Data Table of Bacon vs. Cooking Time
Number of pieces of Bacon Cooked in Batch Number of pieces of Bacon Burned Cooking Time (minutes) 20 2 4 6 1 8 18 10 12 14 16

Results Results are written up, often with the aid of graphs
Will include any calculations made, and the formulas used to make them Tell if results make sense are the mistakes insignificant enough to give credibility to the data? Usually include Percent yield Percent error

% Error = ׀ Experimental value- Theoretical value ׀ x ( 100%)
Results Percent yield How much you got from the expected amount % Yield = mass of Actual Yield x ( 100%) mass of Theoretical Yield Percent error How close your answer is to the actual answer % Error = ׀ Experimental value- Theoretical value ׀ x ( 100%) Theoretical value

The Effect of Cooking Time on Bacon
pieces of burned bacon (number) The Effect of Cooking Time on Bacon Dependent Variable (you observe) Cooking time (minutes) Independent Variable (you control) In this case, you are observing how many more pieces of bacon are burned with a change in cooking time.

Graphing in science: How we display data
Always title your graph Make sure it is about what you are graphing Always Independent variable Vs. Dependent variable The x-axis is always the independent variable; the y-axis the dependent variable Label the x and y axes, and use units with these labels

Use a line graph (scatter plot) when you are trying to show how two things relate to each other such as the dependent and independent variable unless you are comparing numbers of things which is NOT about comparing dependent and independent variables Then use a pie chart or a bar graph A good rule of thumb is that units imply a line graph, counting or percentage implies another type of graph

Use a best fit line for the line graph/ scatter plot Do not just connect all the dots Use the space you are given If you have a full page, take up the page Using only a 10cm by 10cm square when you have a full page makes it much harder to read and get your point across

The Effect of Cooking Time on Bacon
pieces of burned bacon (number) The Effect of Cooking Time on Bacon Dependent Variable (you observe) Cooking time (minutes) Independent Variable (you control) In this case, you are observing how many more pieces of bacon are burned with a change in cooking time.

Evaluation: The Arrows
How do you know if your results are acceptable?

Evaluation Did you test your hypothesis?
Were your sources of error significant? Where they acceptable? Were your data/ results within acceptable ranges? Accurate? Precise? Or are you making claims you can not justify? Can this go any further? Be modified to learn more? Reflections?

Article Evaluation Is this “good” science? Why or why not?
Can you think of even one different explanation for what happened? If so, what is it? Did the test really, really truly, unquestionably, completely test what the author thought he was testing? Is the scientist honest with himself about how well his idea explains everything? Could it be wishful thinking?

After we know something
Assuming we are happy with the results, what happens when we are pretty darn sure we know something, and scientists recognize it as truth?

When experiments lead to knowledge: Laws and Theories
If it all makes sense, and is supported, science incorporates that new knowledge into scientific knowledge as a whole in the form of a law or a theory

Laws Statement of what happens without explaining why
It is a generalized relationship Usually covers a small set of patterns/ behaviors We can not not do it Unbreakable so far Usually has mathematical support

Theory A hypothesis, or series of hypotheses, that have been tested extensively and have not been rejected Covers a broad number of concepts/ behaviors/ observations Explains why/ how things happen Make predictions based up on As close to truth as you can get

Relating laws and theories
Boyle’s law relates pressure and volume Pressure and volume of a gas in a sealed container have a direct relationship; if one changes, the other changes in response P1V1=P2V2 The kinetic molecular theory explains Boyle’s law and can be used to predict gas behavior Molecules moving exert pressure that pushes on the walls of a flexible container; as that pressure changes, the volume changes accordingly

But how do we know if we are right
But how do we know if we are right? Evaluation of the Experiment and Resulting Data

Accuracy and Precision
A sidebar before we talk about using numbers in evaluation more…..

Hitting the intended target/ getting the accepted value Being right
Accuracy Hitting the intended target/ getting the accepted value Being right

Hitting the target repeatedly or getting the same value repeatedly
Precision Hitting the target repeatedly or getting the same value repeatedly Also refers to the specificity of the measurement How exact an answer is: to what place the answer is reported to By use of significant digits (which we’ll get to shortly)

Accepted value/ target
Accuracy depends upon the definition of accurate for that particular situation Ex: +/- 5% is OK for lab percent yield, but an unacceptable error for not hitting pedestrians while driving

Random Measurements Measurements do not have precision--they do not cluster around the same value. Measurements are probably not accurate-the average does not represent the true value. An accurate average does NOT make you accurate!

Are the following accurate? Precise? Neither?

Can you be accurate and not precise?

Yes- you can “hit the target” one time, but it would only be defined as accurate depending upon how specifically (precisely) you would be defining the acceptable value

Can you be precise but not accurate?

Yes. You might be getting the same wrong answer, within a narrow range, repeatedly

Error: 2 types Systemic error
Happens because of the instruments or methods used is consistently flawed can be accounted for and adjusted for to get the “real” value ex: the balance measures 0.05g heavy on every measurement Corrected by subtracting 0.05g from all measurements

Random error not a consistent part of the instruments or methods used
can not be accounted and adjusted for as it is not predictable Examples Not zeroing (tareing) the balance before a measurement Contamination of a measuring device

Errors vs. Uncertainty in Measurement
Errors in measurement are not the same as uncertainty Humans mess up Measuring instruments themselves are not 100% flawless Both of these errors can be random or systemic Error means it is done wrong, and uncertainty is not incorrect, just the limit of the measuring instrument

Uncertainty in Measurement
ALL measurement involves some uncertainty, because all measurements involve some rounding. Not an error, as long as you are rounding to the proper place Defined by the markings on the instrument you are using You are to go one decimal place PAST the markings on the instrument

Measurements and Estimation
You are told to draw a line 35.5cm long using a regular ruler with marks for each millimeter When you measure it out, you know that you are correct with the 35, but you had to estimate the .5 portion You can be a little over or a little under Up to 0.05cm (.5mm) up (to 35.55cm) or down (to 35.45cm); you estimate one place past the smallest marks on the ruler B/c both would round to 35.5cm

Rounding Examples: Remember when rounding to a place
Look to the NEXT place ONLY (not past that) Round down for 4 and below Round up for 5 through 9 Examples: L rounded to the ones place is 223L You look at and ignore the rest, 4 rounds down L rounded to the tenths place is 223.5L You look at and ignore the rest, 5 rounds up

Practice Rounding Round the following to the hundreds place
34, 345 52, 299 2,303 Round to the hundredths place

Practice Rounding Round the following to the hundreds place
34, ,300 52, , 300 2, Round to the hundredths place

How to Measure The last digit is always estimated
See How to Read a Graduated Cylinder This is why we use significant digits in calculations

Measurements and Estimation
The measurement has 3 digits to read 55.6mL 2 known: 55mL 1 estimated: 0.6mL It can be a little off To round to 55.6mL (and not be 55.5mL or 55.7mL)

Side note on two types of numbers: Certain and Uncertain
Certain (known) numbers When you make a true count of something, it is exact The number of people in PHS The number of hours in the day Can be a definition of a unit: Applies only to conversions within the same system (metric-metric or English-English) 12In = 1ft 1m= 100cm

Uncertain numbers: Estimates
Rounding a count 1300 students in PHS, not the exact count Conversion factors that are not definitions Metric- English/ English-Metric 1cm= in We’d usually round to something here as this is too long to use, as would be the answer from using this conversion Measurements Include the certain digits and a last estimated digit

Math in Chemistry: Some new, mostly review: Significant Digits
Math in Chemistry: Some new, mostly review: Significant Digits Scientific Notation System Internacional (SI) Metric system Unit Conversions Dimensional analysis

Significant Digits (AKA: Significant Figures)
Precision in Measurement

Significant Figures Tell us how good (precise) our measurement or calculation is Where the known digits and estimated digit are Are the digits that are important for calculations and ensure that you do not carry out an answer to the 23rd decimal place when doing a calculation You don’t just pick the first three numbers, or 3 decimal places You use the number of significant digits in the calculation to determine the number of digits in the answer

Significant Figures in Measurements
Significant digits include the known digits and the last (estimated) digit in a measurement. 8.45mL has three significant figures 8 and 4, which are known 5 which is estimated You can’t read more than this on this graduated cylinder Read one digit past the markings In this case, to the hundreds place

Working with Numbers: Significant Digits
In a count of something, all digits are significant because we know that all numbers are exact How can you tell how many digits in a measurement are significant? All non-zero numbers are significant Zeros are what you need to think about Zeros that are Significant In the middle of a number. 202 Zeros that are Not Significant When it’s a placeholder. Before a number: At the end when there is NOT a decimal point: 200

Significant Figures: Zeros
all zeros are significant in Between non-zero numbers Or following a decimal point no zeros are significant in All are placeholders zeros MAY be significant in 2000 Depends on if it is a count or a measurement Yes if a count No if a measurement because they would be placeholders

Significant Digits The following three measurements have very different degrees of precision, and therefore a different number of significant digits: 100g 100.g 100.0g

Significant Digits (Significant Figures)
100g rounded to the hundreds place the real value is between 1 significant digit 100.g rounded to the ones place the real value is between 3 significant digits 100.0g rounded to the tenths place the real value is between 4 significant digits The difference is the presence of a decimal

Practice Problems Give the number of significant figures in:
1025 km 2.00 mg 520

Practice Problems Give the number of significant figures in:
1025 km Four (zeros between nonzero digits are significant) 2.00 mg Three (both zeros are significant) Three (only the final zero is significant) 520 Two (if measured to the nearest ten)

The Atlantic- Pacific Rule: A trick to count significant digits
The Atlantic- Pacific Rule: A trick to count significant digits Pacific Ocean Point Present count from this side Atlantic Ocean Point Absent count from this side Start with first non-zero number

Significant Figures in Addition and Subtraction
Line up the decimal points of the measurements to be added or subtracted Perform the mathematical operation Round off the answer to the smallest number of decimal places in a measurement For example: = 5.0

Significant Figures and Multiplication or Division
The measurement containing the fewest significant figures determines the number of significant figures in the answer. Example 1: m x 0.2 m = 0.56 = 0.6 m2 since 0.2 only has 1 significant digit, and 2.8 has 2 significant digits, the answer must have only 1 significant digit Example 2: mi / 3.2 hr = = 79 mi/hr Since 3.2 has 2 significant digits, and 252 has 3 significant digits, the answer must have 2 significant digits

Representing numbers large and small
Scientific Notation Representing numbers large and small

Using Exponents (Scientific Notation)

Scientific (Exponential) Notation
Conveniently expresses very large or very small numbers 245, 000, 000 is 2.45 X108 2.45E8 is also acceptable is 1.2 X10-8 1.2E-8 is also acceptable Unambiguously expresses the number of significant figures All the digits before the X10 (or the E) in scientific notation are significant Remember the 100g, 100.g, and the 100.0g?

Scientific Notation and Significant Digits
Number Number of Sig Figs Scientific Notation 100g 1 1E2g 100.g 3 1.00E2g 100.0g 4 1.000E2g Scientific notation allows us to express this measurement with 2 significant digits while normal numbers do not. 1.0E2g would tell us that the balance rounded to the tens place

How to Convert a Number to Scientific Notation
Convert the number you’re converting into a number between 1 and 10 by moving the decimal either to the left or to the right. Write the number that you came up with in step one, followed by “x 10”. (You can also use E in place of this) Recall how many decimal places you moved the decimal point in step one. If the number that you’re converting is greater than 10, write a positive number as a superscript above the “x 10” from step 2. If the number you’re converting is less than one, write a negative number.

Practice Problems: Write these numbers in normal format
4.2 x 103 2.50 x 106 4.890 x 103 4.35 x 102 7.34 x 10-5 6.830 x 10-2 1.32 x 103 7.32 x 10-4

Practice Problems: Write these numbers in normal format
4.2 x 103 2.50 x 106 4200 4.890 x 103 4.35 x 102 435 4890. 6.830 x 10-2 7.34 x 10-5 7.32 x 10-4 1.32 x 103 1320

Practice Problems: write these numbers in scientific notation
45,500 45, 500. 0.0045 250 7,300

Practice Problems: write these numbers in scientific notation
45,500 4.5E4 2.34E-4 45, 500. 4.5500E4 0.0045 4.5E-3 250 2.5E2 2.50E-4 7,300 7.3E3

You ARE going to use it The English System is not allowed in Science
The Metric System You ARE going to use it The English System is not allowed in Science

Units and Types of Measurement

Metric Prefixes: why we care
Giga G 1,000,000, Mega M 1,000, kilo K 1, deci d centi c milli m Micro µ nano n pico p 1/13/2018 1.4

Metric Conversion Articles
Small Group Discussion [A, B, C, D] What happened in your article? Why did it happen? How could this be avoided in the future? Large Group Discussion How are all of the articles connected? Should the U.S. change to the S.I. (or metric) system? What problems would there be because of the change?

Why SI? Because it is: Standard the whole world uses it
Why SI? Because it is: Standard the whole world uses it Except the US, Liberia, and Myanmar (Burma) Base 10 Easy conversion between units Units make more sense than English units

Unit Conversions Dimensional Analysis

Dimensional Analysis and Conversion Factors
Dimensional analysis is a systematic approach for solving problems by multiplying a measurement by one or more conversion factors with units. Conversion factors are ratios or fractions derived from definitions or equalities 3 ft = 1 yd 16 oz = 1 lb.

Conversion Factors 1 yd = 3 ft The unit you want goes on the top
Each equality can be written as two conversion factors The equality below gives the two conversion factors on the right: The correct one to use depends on which unit you want your answer in The unit you want goes on the top 1 yd = 3 ft

Sample Problems How many feet are there in 25 yards?
How many yards are there in 12 ft?

Practice Problems How many ounces are there in 3.5 lb?
How many gallons are there in 12 quarts?

Practice Problems How many ounces are there in 3.5 lb?
How many gallons are there in 12 quarts? Notice that the answers have the correct number of sig figs required for multiplication: the least number of SFs in the numbers present

Metric to Metric Conversions
Metric to metric conversion factors are derived from the definitions of metric prefixes. These are exact numbers with unlimited Sig Figs Because they are definitions 0.1 meter = 1 decimeter 1 meter = 10 decimeters 0.01 meter = 1 cm 1 meter = 100 cm

Sample Problems How many decimeters are there in 5.5 meters?
How many meters are there in 25 centimeters?

English to Metric Factors
English to Metric conversion factors are derived from tables of equivalent values, for example: Remember that you need to keep in mind that these conversion factors are estimated, not exact, like conversions within the same system

Practice Problems How many grams are there in 125 pounds?
454 g = 1 lb 1 L = 1.06 qt cm = 1 in How many grams are there in 125 pounds? How many inches are there in 8.7 meters?

Temperature Scales Freezing point of water: 32º F = 0º C = 273 K
Boiling point of water: 212º F = 100º C = 373 K

Temperature Conversion
Fahrenheit degrees are smaller than Celsius But the Fahrenheit scale is scientifically unimportant 100 º C is the equivalent of 212 º F 0 º C is equivalent to 273K Based on 0K as the lowest temperature possible ºF = 1.8* ºC + 32 º ºC = (ºF - 32 º) / 1.8 K= ºC

Practice Problems K= ºC + 273 and ºC = K - 273 What is 75.0 º F in ºC?
ºC = (75 º F- 32 º ) / 1.8 = 23.8 ºC But use a ºC thermometer and you’ll never need to convert Take ALL temperatures in ºC What is -12 º C in ºF? Who cares? You’ll NEVER EVER go from ºC to ºF in this class, b/c ºF is irrelevant in science classes It’s 10.4 ºF, for the record (1.8)(-12) +32=10 in case you needed to know What is 100 ºC in K? 100º C + 273= 373K Kelvin scale IS important to chemistry Know K to ºC conversions and ºC to K conversions K= ºC and ºC = K - 273

The Central Science Chemistry is called “The Central Science” because it overlaps so many sciences.

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The Central Science Chemistry is called “The Central Science” because it overlaps so many sciences.

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