INTRODUCTION AND MEASUREMENT How can we think like scientists? What is Chemistry? Why study Chemistry? How can problems be solved in a systematic manner?

INTRODUCTION AND MEASUREMENT

• How can we think like scientists?• What is Chemistry?• Why study Chemistry?• How can problems be solved in a systematic manner? • How do we give meaning and dimension to our

descriptions of the world around us? • How do round off answers to math problems? • How is the data compression in mp3 and ZIP files mirrored

in scientific notation? • How can units be used to solve problems? • How can we make sense of data and use it to make

predications?

AIM: How can we think like scientists?

• Do Now:

1. Have color coded PT out on table

2. Have signed contract on table

3. Read the instructions on the NOS Activity worksheet

Nature of Science Activity

Conclusion

• Brainstorm ideas about how this activity is similar to “doing” science?

• Hand in one sheet per table

• Put all pieces back in the bag, keep the extra piece separate

AIM: What is Chemistry?

• Chemistry is the study of the composition of substances and the changes they undergo

• It is the science of matter. It is considered the interaction between atoms

• Everything has chemistry, actually all matter has chemicals in it which is chemistry. For example, a table, a book, ink, and even us!

3. Analytical chemistry: the study of the quantitative composition of substances

Examples: how much chlorine is in a sample of tap water

4. Biochemistry: the study of chemistry of living organisms

Examples: how sugar in the blood stream of cats affect insulin production

AIM: What is Chemistry?

There are several divisions or branches of chemistry:

1. Organic chemistry: the study of substances that contain carbon

Example: How gasoline is produces from oil

2. Inorganic chemistry: the study of substances without carbon

Example: how table salt reacts with different acids

Divisions of Chemistry

AIM: Why study chemistry?

• Helps us understand the world around us better

• Many questions can be answered by chemistry

• Anything you touch, taste or smell is a chemical. When we study chemistry we know a bit more about how things work

AIM: Why study Chemistry?- everyday examples

1. Digestion; enzymes promoting chemical reactions that power our bodies. Lifting your arm requires your body to make and burn ATP using oxygen with carbon dioxide as one of the waste gases produced.

2. The internal combustion engine takes liquid gasoline, converts it to a gas, burns it takes the waste to make mechanical energy and then expels some noxious gases. The rare metals in the catalytic converter scrub out the sulfuric acid, but we still get the ingredients for smog out of them.

3. Cooking is the heating and combination of compounds to make something new. In some cases, like rising bread we have an actual chemical reaction where the yeast changes the food.

4. When concrete dries and hardens the water actually causes a chemical reaction with the cement making a binding action drying concrete isn't just losing water it is undergoing a chemical change and one that creates heat as well (an exothermic reaction).

5. When you write with ink on paper, the ink and paper unite in a chemical reaction so that you can't erase it. Specialized inks allow a short period where you can erase some inks, but most inks dry and can't be erased; they have bound with the paper. This includes your pen and your ink jet printer.

6. Plastics are all about organic chemistry.

7. The sun undergoes fusion and yes that too is chemistry. It creates radiation and photons so we can see. Some of the radiation interacts with oxygen to create ozone and the ozone layer shields us from harmful UV radiation.

8. ANYTHING that burns is undergoing a chemical reaction and almost always creates some form of carbon as waste.

AIM: Why study Chemistry?- everyday examples

AIM: How can problems be solved in a systematic manner?

• The scientific method is a way to solve a scientific problem. It is an approach to a solution (using mostly common sense)

1. Objective (Problem): statement of purpose

2. Hypothesis (Prediction): Educated guess, in the form: if …. then…

3. Experiment (Test): to test hypothesis, must give reproducible results to be reliable

Variable: factor being tested Control: other factors that are held constant


- Steps of the Scientific Method

4. Observations (Data): collect and gather data based on your observations; organize these results to perform analysis in the form of charts, tables or graphs

5. Conclusions: the determination if your hypothesis was correct, it may be accepted, rejected revised

6. Follow up/application: a repeat with modification is sometimes necessary, and a reevaluation of the results. Also answering one question often leads to new questions. How could you use and communicate the information of your experiment. Why is it important and who could benefit from it?


- Steps of the Scientific Method

Theory: explains the results of experiments, they can change or be rejected over time because of results from new experiments

Law: describes natural phenomena, it tells what happens and does not attempt to explain why the phenomena occurs (that is the purpose of a theory). Laws can often be summarized by a math equation


- Law vs. Theory

AIM: How can we give meaning and dimension to our description of the world around us? – Metric System

• Measurement gives the universe meaning! How tall are you? How much do you weigh? How old are you? How fast can you run? How much volume do you displace? All of these questions are designed to give us reference to the world around us.

AIM: How can we give meaning and dimension to our description of the world around us? – Math Rules for Chem

• Atlantic and Pacific Rule:

• If a decimal point is present (Pacific side) you start counting from left to right with the first non zero number

• If a decimal point is absent (Atlantic side) you start count from right to left with the first non zero number

AIM: How can we give meaning and dimension to our description of the world around us? – Sig Fig Rules

Examples:

1. 23.285 cm ________________

2. 8000 sec ________________

3. 40. L ________________

4. 2300 g ________________

AIM: How can we give meaning and dimension to our description of the world around us? – Sig Fig Rules

5

1

2

2

AIM: How do round off answers to math problems? – Calculating with sig figs

Multiplication and Division: want your answer to have the same number of SIG FIGS as the measurement that has the least number of sig figs

Examples:

1. 3.1415 x 2.25 =

2. 48.2 cm x 1.6 cm x 2.12 cm =

3 SF

2 SF

7.07

160

AIM: How do round off answers to math problems? – Calculating with sig figs

Addition and Subtraction: want your answer to have the same number of DECIMAL PLACES as the measurement that has the least number of DECIMAL PLACES

Examples:

1. 6.357- 2.4 = 2. 3.842 cm + 8.51cm + 16.324 cm =

1 DP

2 DP

4.0 28.68 cm3

AIM: How is the data compression in mp3 and ZIP files mirrored in scientific notation?

- sci notation


- sci notation


- sci notation

• Comparing relative magnitudes of two numbers in scientific notation:


- sci notation

AIM: How can units be used to solve problems? - dimensional analysis

• To covert a measurement from one metric unit to another, you must know the difference in magnitude between the two prefixes and use the to create a conversion factor


• Use Reference Table C. If there is no prefix (m, g, L, etc.) then the power of ten is 100 . The prefix is underlined so you can verify its magnitude against Reference Table C. The smaller unit is italicized

TO USE THE CONVERSION FACTOR: **NOTES: the number of sig figs in your final answer equals the number of sig figs in the number you are converting **

• Given amount multiplied or divided by the conversion = answer

• If the given unit is also the numerator unit on the conversion factor, then DIVIDE to cancel it out

• If the given unit is also the denominator unit on the conversion factor, then MULTIPLY to cancel it out


DIMENSIONAL ANALYSIS

- Convert a given result from one system of units to another

- Unit factor method

Ex 1) A pin measuring 2.85 cm in length. What is its length in inches?

• Need an equivalence statement

2.54cm = 1in

• Divide both sides by 2.54cm

• Unit Factor

• Multiply any expression by this unit factor and it will not change its value

Ex 1) A pin measuring 2.85 cm in length. What is its length in inches?

• Pin is 2.85cm need to multiply by the unit factor

Ex 2) A pencil is 7.00 in long. What is the length in cm?

• Convert in cm

• Need equivalence statement 2.54cm = 1in

• Unit Factor


• Unit factors can be derived from each equivalence statement

2.54cm = 1in

• 2 unit factors

and


and

• How to choose – look at direction of required change

• in cm (need to cancel in – goes in denominator)

• cm in (need to cancel cm – goes in denominator)

Ex 3) You want to order a bicycle with a 25.5in frame, but the sizes in the catalog are given

only in cm. What size should you order?

Ex 4) A student entered a 10.0-km run. How long is the run in miles?

• km mi

• Equivalence statement 1m = 1.094yd

• Strategy first

km m yards mi

• Equivalence statements:

1km = 1000m

1m = 1.094 yd

1760yd = 1 mi


• km m

10.0𝑘𝑚𝑥1000𝑚1𝑘𝑚

=1.00 𝑥104𝑚


• m yd

1.00 𝑥104𝑚𝑥1.094 𝑦𝑑1𝑚

=1.094 𝑥 104 yd


• yd mi

• Original 10.0 which has 3 sig figs so you want 3 sig figs in your answer

1.094 𝑥104 yd 𝑥1𝑚𝑖

1760 𝑦𝑑=6.216𝑚𝑖=6.22𝑚𝑖


• Can combine all conversions into one step

10.0km 𝑥1000𝑚1𝑘𝑚

𝑥1 .094 𝑦𝑑1𝑚

𝑥1𝑚𝑖

1760 𝑦𝑑=6.22𝑚𝑖

AIM: How can we make sense of data and use it to make

predications? - graphing

• Changing one thing in an experiment (independent variable) will often cause something else to change (dependent variable)

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INTRODUCTION AND MEASUREMENT How can we think like scientists? What is Chemistry? Why study Chemistry? How can problems be solved in a systematic manner?