Chapter 1 Chemistry and You

Section 1 What is Chemistry?

Definition of Chemistry The study of all substances and the changes that they can undergo.

“The Central Science” Chemistry overlaps many sciences

Why Study Chemistry? It’s fun! It will help you understand the world around you. It opens up many new doorways.

How to Study Chemistry Do not memorize isolated facts! Work on understanding concepts first. Use classroom discussion as a process of discovery. Learning will follow naturally.

Section 2 The Scientific Method

Michael Faraday Discoveries led to future growth and applications, but did not have much original practical value.

The Scientific Method A way of answering questions about the world we live in.

Step 1: Observation A scientist observes something, which provokes a question. Sometimes the question may come first, as science is based on curiosity.

Step 2: Hypothesis A scientist generates an inferred answer to the question. In order to be considered a hypothesis, it must be testable!

Step 3: Experiment A scientist manipulates one variable at a time and carefully records data. An experimental control is used as a baseline. The data is then analyzed and further experiments are performed.

Step 4: Conclusion The result of the experiment. Will likely generate new questions and hypotheses, which lead to new experiments. IT’S A CYCLE!

Step 5ish: Natural Law After several experiments, conclusions may be summarized into a natural law (also known as a scientific law). Describes how the natural world behaves but not WHY it does so.

Step 5ish: Theory A scientific theory explains WHY the natural world behaves as it does. It answers all questions raised in the experiments used to generate it, as well as being checked by future experiments.

Sample Problem 1 Pages 10-11

Safety in the Laboratory Section 3 Safety in the Laboratory

The Rules Follow Mr. Leuenberger’s directions Notify Mr. Leuenberger of problems Know how to use the safety equipment Wear approved safety goggles If you have long hair, tie it back

The Rules Avoid awkward transfers of chemicals If it’s hot, let it cool Carry chemicals with caution Dispose of chemical wastes properly CLEAN UP AFTERWARD!

Test You will take a safety test tomorrow. You will not be permitted to participate in lab until you pass the test.

Section 4 Units of Measurement

Metric System The international system of measurement. Ironically known as the English system. Get used to it!

International System of Units Base Units Length-meters (m) Mass-kilograms (kg) Time-seconds (s) Quantity-mole (mol) Temperature-kelvin (K) Electric Current-ampere (A) Luminous intensity-candela (cd)

Mass and Weight Mass: The amount of matter in an object. Weight: The force of attraction due to Earth’s gravity.

International System of Units 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)

Non-SI Units Liter (L) Celsius degree (°C) Pressure Energy 1000 L = 1 m3 Celsius degree (°C) 0°C = 273.15 K Pressure Atmosphere (atm) Millimeters of mercury (mm Hg) Energy calorie (cal)

Prefixes T-tera-1012 G-giga-109 M-mega-106 k-kilo-103 d-deci-10-1 c-centi-10-2 m-milli-10-3 µ-micro-10-6 n-nano-10-9 p-pico-10-12

Practice! Convert 0.000 05 Gs to s. Convert 323 µg to kg. Convert 970,000,000,000 pL to ML.

Uncertainty in Measurement Section 5 Uncertainty in Measurement

Measurements Measurements are uncertain for two reasons: Measuring instruments are never completely free of flaws and measuring always involves some estimation.

Estimations Digital display: The final digit is the estimated digit. Think of a digital clock. Analog display: estimate one digit beyond what you know for sure. With liquids, take the measurement at the bottom of the meniscus.

Precision A precise measurement will give the same result multiple times under the same conditions.

Accuracy An accepted value is what the result should be. Accuracy is how close to the accepted value the result is.

Section 6 Working With Numbers

Significant Digits The certain digits and the estimated digit of a measurement are together called the significant digits of the measurement.

Zeroes Atlantic-Pacific Rule Divides into two categories: With a decimal point and without. If present, count from the Pacific side. If absent, count from the Atlantic side.

Practice! 156.98 mL 0.0097 pm 170,000 cg 8900.0098 kJ 870 µs 870. GN 0.00870 dV

Calculations Use the lowest number of significant digits. If lower than 5, round down. If 5 or greater, round up.

More Practice! 87.98 g + 28.9 g 90. mL – 87.07 mL 0.012 km × 1200 km

Scientific Notation Separates a number into two parts. The first part is only the significant digits The second part is a power of ten written in exponential form (10n) 1000 = 10 × 10 × 10 = 103

Even More Practice! 5600 kJ 0.0009393 Mm 98,000,000,000 pL 0.000 000 000 000 000 000 000 323 s

Percent Error Can be positive or negative

Ratios Typically expressed in units representing the ratio, i.e. x g/cm3.

One Last Practice! What is the speed of an object that traveled 50 meters in 10 seconds? What is the density of an object that has a volume of 100 cm3 and a mass of 1000 g? What is the density of an object that has a mass of 850. mg and has a volume of 12,000 m3? (Your answer should be in g/cm3.)

Section 7 Problem Solving

Dimensional Analysis The technique of converting between units. A unit equality is an equation that shows how different units are related. A conversion factor is an equation that is always equal to 1.

Using Conversion Factors Essentially multiplying the equation by 1. Units cancel each other out.

Practice! How many inches are in 500 centimeters? How many mm Hg are in 3.4 atm? How many hours are in 1200 s?

Impossible Conversions Can you change kilograms to seconds? NO!

Four Steps Analyze Plan Identify your unknown quantity and organize your information. Sketches can help! Plan Find out if the problem is similar to a past problem for clues and equations that may be useful. Make a plan for how to solve the problem and estimate the answer.

Four Steps Solve Evaluate Perform the mathematical steps in your plan. Be aware of units and significant digits. Evaluate Does the answer make sense? Compare with your estimate.

Graphing Shows the relationship between two experimental variables. Trends can be spotted when points from data are placed on a graph.

More Practice! Make a graph of the following data. Is there a trend? Predict the volume at 4 g and 60 g. Mass Volume 3 g 18 L 7 g 42 L 12 g 72 L 15 g 90 L 21 g 126 L