Chapter 1: Chemistry and You Explain why a knowledge of chemistry is central to many human endeavors. List and describe the steps of the scientific method. Explain the basic safety rules that must be followed when working in the chem lab. Identify the metric units of measurement used in chemistry. Explain what causes uncertainty in measurements. Compare accuracy and precision. Explain how to use significant figures and scientific notation. Calculate percent error. Define density and explain how it is calculated. Explain how dimensional analysis and conversion factors are used to solve problems in chemistry.

Vocab Chemistry Scientific method Observation Hypothesis Experiment Conclusion Natural law Theory Variable Experimental control Metric system International System of Units (SI) Base unit Mass Volume Metric prefix Precision Accepted unit Accuracy Significant digit Percent error Density Dimensional analysis Conversion factor

Chapter 1: Chemistry and You Look at the pic on p. 2 and read the caption Name some of the basic chemical substances that make up your body. Name some other chemical processes, besides digestion, that occur in your body. Can you think of an important chemical reaction that occurs in plants and trees?

Section 1-1 What is Chemistry?

Chemistry in Action Chemistry is a broad science that touches nearly every aspect of human life. What are some ways chemistry affects the 2 careers mentioned in the section? Examining a wetlands habitat Preserving historical artifacts

The Central Science Chemistry has been called the central science b/c it overlaps so many sciences Careers that use chemistry Hair stylists Construction Biologists What others? Possible chemistry careers Police departments (CSI) Perfume companies Research chemists

Why Study Chemistry? It is involved in many aspects of life Helps you to understand the world around you

Cleaning Priceless Art Read the “Connection” box on p. 6 What occupation is using chemistry? What did they do to clean the art? Why are some people upset about their actions?

Section 1-2 The Scientific Method

Theory modified as needed The Scientific Method Observation Question Hypothesis Experiment Conclusion A way of answering questions about the world we live in Oscar Has Extremely Colorful T- Shirts Theory (Model) Natural Law Theory modified as needed Prediction Experiment

Observation Seeing a problem or asking a question that you cannot answer Always leads to a question

Hypothesis An educated guess Usually asked in a “cause-effect” statement Must be able to test the hypothesis

Experiment A test of the hypothesis Data will be collected and analyzed Must have 1 variable and at least 1 constant Variable – the particular factor being tested

Conclusion The result of the analyzed data May agree or disagree with your hypothesis

Theory Answers the original question as well as any others formed during the process Predicts the results of further experiments

Scientific/Natural Law Describes how nature behaves but not why

1-2 Section Review On looseleaf to turn in, page 13 (1-5)

Bikini Bottom Experiments With your small group, complete the SpongeBob worksheet SpongeBob Scientific Method.pdf

Section 1-3 Safety in the Lab

Section 1-4 Units of Measurement

Units of Measurement Measurement: always includes a number and unit If someone is 7 feet tall, “7” is the number and “feet” is the unit Saying someone is 7 does not tell you enough info They could be 7 yrs old, 7 feet tall, 7 inches tall, … Feet and inches are part of the English system of measurement In science, we use the Metric system All scientists, no matter their country or language, use the metric system

United States, Liberia, and Burma

International System of Units SI units used by all scientists around the world Based on 7 metric units called base units Length meter (m) Mass kilogram (kg) Time second (s) Count/Quantity mole (mol) Temperature Kelvin (K) Electric Current ampere (A) Luminous Intensity candela (cd)

Derived Units Area square meter (m2) Volume cubic meter (m3) Force Newton (N) Pressure Pascal (Pa) Energy joule ( J ) Power watt (W) Voltage volt (V) Frequency hertz (Hz) Electric charge coulomb (C)

Units Science is a process, not a collection of rules The most frequently used units in class that differ than SI: Temperature - Celsius (˚C) Volume – liter (L) Pressure – atmosphere (atm) millimeters of mercury (mmHg) Energy – calorie (cal)

Commonly used units Length Mass Volume A dime is 1 mm thick A quarter is 2.5 cm in diameter Average height of a man is 1.8 m Mass A nickel has a mass of 5 g A 120 lb woman has a mass of about 55 kg Volume A 20 oz can of soda has a volume of 360 mL A ½ gallon of milk is equal to 2 L

Metric Prefixes King Henry Died by drinking chocolate milk Abbreviation Meaning kilo- k 1 000 hecta- H 100 deca- D 10 Base Unit 1 deci- d 0.1 centi- c 0.01 milli- m 0.001 King Henry Died by drinking chocolate milk Base units include meter, liter, second, gram

How to Use Prefixes kilo- hecto- deca- Base units deci- centi- milli-

Example How many millimeters are in a meter? 1 meter = mm kilo- hecto- deca- base units deci- centi- milli-

Practice Problems Convert a volume of 16 deciliters into liters Convert 1.45 meters into centimeters 145 cm Convert a volume of 8 deciliters into liters 0.8 L Is 5 centimeters longer or shorter than 8 millimeters? Explain. 5 cm is longer than 8 mm b/c 0.05 m is greater than 0.008m

Metric Mania Worksheet

Section 1-5 Uncertainty in Measurement

Making Measurements When making a measurement, write down everything given to you with one uncertain estimated number 5.1 inches is easy to spot but we still need 1 uncertain number My estimation = 5.12 inches Measurements are uncertain b/c: Measuring instruments are never completely free of flaws Measuring always involves some estimation

Reliability in Measurement Precision: the same result is given over and over under the same conditions Accuracy: the result is close to a reliable standard Accepted value: the reliable standard High Precision High Accuracy

Section 1-6 Working with Numbers

Working with numbers Measurements are rarely used just by themselves. Usually used in some form of mathematics (+, -, x, or ÷) Produces values of mass, temperature, volume, etc.

Significant Figures (Digits) The certain digits and the estimated digit of a measurement Example: In the # 31.7, there are 3 sig figs The 3 and 1 are certain digits while the 7 is the uncertain digit

Rules for Sig Figs Nonzero #: any number that is not a zero Zeros Never count “leading zeros” 0023  only count the 2 and 3 0.054  only count the 5 and 4 Always count “captive” or “sandwiched” zeros 303  count the 3, 0, and 3 “Trailing zeros”: zeros to the right Only count if used with a decimal point 5400  only count the 5 and 4 5.400  count the 5, 4, 0, and 0

Example How many sig figs are in 0.057 010 g? Nonzero numbers: Captive zeros Trailing zeros when there is a decimal Final Answer 5 significant figures

Practice Problems How many sig figs in the following numbers? 19.0550 kg 6 sig figs 19.0550 3500 V 2 sig figs 3500 1 809 000 L 4 sig figs 1 809 000 95 600 m 3 sig figs 95 600 520 mL 2 sig figs 520 0.0102 ms 3 sig figs 0.0102

Sig Fig Practice Wkst

Significant Figures in Calculations Multiplying and Dividing The answer will have the same # of sig figs as the measurement with the smallest # of sig figs Volume = 3.052 m x 2.10 m x 0.75 m (4 sig figs) (3 sig figs) (2 sig figs) = 4.8069 m3 = 4.8 m3

Sig Figs in Calculations Adding and Subtracting The answer will have the same # of decimal places as the measurement with the smallest # of decimal places 951.0 g 1407 g 23.911 g + 158.18 g 2540.091 g Since there aren’t any decimals in 1407, our answer will not have decimals Final answer = 2540 g

Practice Problems 6.15 m x 4.026 m = 1.45 m x 1.355 m x 2.03 m = 0.3287 g + 45.2 g = 45.5287 g = 45.5 g 0.258 mL ÷ 0.361 05 mL = 0.71458246 mL = 0.715 mL

More Practice Worksheet

Scientific Notation In science we work w/ very large and very small #s For example: 1 drop of water contains = 1,700,000,000,000,000,000,000 molecules The mass of 1 proton = 0.000 000 000 000 000 000 000 000 001 672 62 kg

Scientific Notaion To make it easier for ourselves, we use scientific notation 1 drop of water contains = 1,700,000,000,000,000,000,000 molecules 1 drop of water contains = 1.7 x 1021 The mass of 1 proton = 0.000 000 000 000 000 000 000 000 001 672 62 kg The mass of 1 proton = 1.67262 x 10-21

How to make # into scientific notation Write 1700 in scientific notation Write down the full number 1700 Move the decimal until it is right after the first 1-10 number 1700  1700.  1.700 Write down this new number without the zeros 1.7 Place “x 10” after this number 1.7 x 10 Count how many times you had to move the decimal and place that number after the 10 as an exponent If you move to the right = negative exponent If you move to the left = positive exponent 1.7 x 103

Examples 37 700 3.77 x 104 1 024 000 1.024 x 106 0.000 000 003 901 3.901 x 10-9 8960 8.96 x 103 0.000 23 2.3 x 10-4

Percents Data will often be given as a percent If it is a fraction, just divide and multiply by 100 Ex: 900 million kilograms of plastic soft drink bottles are produced each year. 180 million kilograms of them are recycled. 180 million kilograms 900 million kilograms = 0.2 x 100% = 20%

Percent Error A measurement can be compared to its accepted value by finding the percent error % error can be positive or negative Positive = measured value is greater than accepted Negative = measured value is less than accepted measured value – accepted value accepted value % error = x 100%

Example In an experiment dealing with finding the boiling point of water, you performed 3 experiments and found water to boil at 98.4˚C, 98.9 ˚C, and 97.5˚C. What is the average and % error of your data? (Hint: the accepted value of the boiling point of water is 100˚C) 98.4 + 98.9 + 97.5 = 294.8 / 3 = 98.3 % error = (100 – 98.3) / 100 x 100 = 1.7%

Practice Work the problems on your “Accuracy Precision and Percent Error” worksheet from a few class periods ago

Density Density – compares the mass of an object to its volume measured in: grams per cubic centimeters (g/cm3) grams per milliliter (g/mL) Mass Density = Volume

Density Problems If a sample of aluminum has a mass of 13.5g and a volume of 5.0 cm3, what is its density? 2.7 g/cm3

Suppose a sample of aluminum is placed in a 25 mL graduated cylinder containing 10.5 mL of water. The level of the water rises to 13.5 mL. What is the mass of the aluminum sample? (Use the density you found in the problem before this) 8.1 g

A piece of metal with a mass of 147g is placed in a 50mL graduated cylinder. The water level rises from 20mL to 41mL. What is the density of the metal? 7 g/mL

What is the volume of a sample that has a mass of 20g and a density of 4g/mL?

A metal cube has a mass of 20g and a volume of 5cm3 A metal cube has a mass of 20g and a volume of 5cm3. Is the cube made of pure aluminum? Explain. (Hint: Pure Aluminum will have a density of 2.7g/cm3.) 4 g/cm3

Dimensional Analysis Technique of converting between units How many feet are in 86 centimeters? We know 12 inches = 1 foot We also know 1 inch = 2.54 centimeters 86 cm 1 in 1 ft 2.54 cm 12 in = 2.82 ft

Practice Problems Use Fig 1-29 on page 38 to help you solve the following problems How many cubic centimeters are in 2.3 gal? 8 700 cm3 How many meters are in 3.5 mi? 5 600 m How many pascals are in 770 mm Hg? 103 000 Pa How many seconds are in 10.5 hours? 37 800 s How many days are in 12 583 seconds? 0.14564 days

Graphing How to draw a scientific graph Need independent variable (x – axis) the variable being changed Need dependent variable (y – axis) the variable being changed by the independent variable Label each axis Do not connect each dot, use a “line of best fit” Give the graph a title which tells what it is of

Example A balloon is filled with air and attached to the bottom of a large container of water. If the water temperature is changed, by heating or adding ice, the volume of the air in the balloon also changes. Data was collected from taking volume measurements at different temperatures. Independent variable: temperature Dependent variable: volume

Sample Graph Trial Temperature (˚C) Volume (mL) 1 25 101.3 2 30 103.2 35 103.4 4 40 105.0 5 45 106.7 6 50 108.4 7 55 110.0 8 60 111.5 9 65 112.9 10 70 114.2