Unit 1

1. Unit 1 Foundations of Chemistry

2. SECTION A.1 WHAT IS CHEMISTRY? • DEFINITION: the study of the composition of matter and the changes that matter undergoes • Five main areas • Analytical Chemistry • Inorganic Chemistry • Organic Chemistry • Physical Chemistry • Biochemistry

4. SECTION A.2 SCIENTIFIC THINKING AND THE SCIENTIFIC METHOD • Modern science began around the late 16th century with a new way of thinking about the world. Few scientists will disagree with Carl Sagan’s assertion that “science is a way of thinking much more than it is a body of knowledge” (Broca’s Brain, 1979). Thus science is a process of inquiry and investigation. It is a way of thinking and acting, not just a body of knowledge to be acquired by memorizing facts and principles. This way of thinking is called the scientific method.

5. Scientific Method: A logical, systematic approach to the solution of a scientific problem; steps in the scientific method include making observations, testing hypotheses, and developing theories

6. Basic Steps of the Scientific Method Observations (Appendix 1.1 & Appendix 1.2): Information obtained through the senses and often involves measurement. Hypothesis: A proposed explanation for an observation. Experimentation: A repeatable procedure that is used to test a hypothesis Independent (manipulative) variable: The variable that is changed during an experiment. Dependent (responding) variable: The variable that is observed during an experiment Conclusions: A step used to organize and analysis data Organize: making graphs, tables, charts, etc. Analyze: using statistics, mathematical relationships to understand data Scientific Law: A generalization that describes a relationship or behavior in nature that is supported by many experiments (no exceptions) Can be expressed by a mathematical relationship Theory: A broad generalization that explains a body of known facts or phenomena. Can never be proven but are considered successful if they can predict the results of many experiments

7. Connecting Concepts:Being an Informed Citizen Write a paragraph explaining how you can learn about the research that is done by scientists. Then explain how this information could help you be an informed citizen.

8. SECTION B.1 INTRODUCTION TO MEASUREMENT MEASUREMENT: a quantitative description that includes both a number and a unit

9. B.2 INTERNATIONAL SYSTEM OF UNITS (SI)Table D It is important that scientists around the world use the same units when communicating information. For this reason, scientists use the modernized metric system, designated in 1960 by the General Conference on Weights and Measures as the International System (SI) units.The SI system begins with seven basic units, with all other units being derived from them (see Reference Tables). While some of the basic and derived units of the SI system are commonly used in chemistry (mole, Kelvin, kilogram, meter, joule, volt), there are other units that are used in chemistry that are exceptions. Thus, in addition to the SI units, you will find liters used in volume measurements, atmospheres and torr used as pressure units, and Celsius as a temperature indicator.

10. SECTION B.3 METRIC SYSTEM Used in nearly every country in the world the Metric System was devised by French scientists in the late 18th century to replace the chaotic collection of units then in use. The goal of this effort was to produce a system that did not rely on a miscellany of separate standards, and to use the decimal system rather than fractions. Conversion Steps Table C To convert to a smaller unit, move decimal place to the right or multiply BASIC UNIT To convert to a larger unit, move decimal place to the left or divide

11. Practice Conversion Problems • 5.70 g to milligrams 3) 45.0 m to kilometers • 4.37 cm to meters 4) 10 µm to kilometers Converting to a smaller unit so move to the right or multiple by a factor of ______ 3 0.045 km 5700 mg Converting to a larger unit so move to the left or divide by a factor of ______ Converting to a larger unit so move to the left or divide by a factor of ______ 2 6 + 3 = 9 0.0437 cm 0.000000010 km

12. Practice Problems • In your textbook go to page 97 and complete on a separate piece of paper questions 78 and 81 • If you do not finish them in class please complete for homework • If you complete this assignment please let me know and I will give you the homework packet for this unit and you may begin working on it for the remainder of the class.

13. The Metric Conversion Act of 1975 • CCLS Project –Unit One • We will be working on this project in class for two days • Your final project will be due Friday September 14

14. SECTION B.4 RECORDING MEASUREMENTS IN CHEMISTRY • When one reads an instrument (ruler, thermometer, graduate, burette, barometer, balance), she/he expresses the reading as one which is reasonably reliable. For example, in the accompanying illustration, record a reasonably reliable measurement for “A” and “B”. Measurement Reading for “A” = ______________ Measurement Reading for “B” = ______________

15. RULE FOR MAKING MEASUREMENTS: • Estimate one digit beyond what you can actually read on the scale given Partial diagram of a 100-ml graduated cylinder Partial diagram of a Celsius Thermometer Volume of water = ______ Temperature = ______

16. SECTION B.5 SIGNIFICANT FIGURES (Textbook pp 66-67) SIGNIFICANT FIGURES: all the digits that can be known precisely in a measurement, plus a last estimated digit

17. 24.7 m 0.743 m 714 m Each of these measurements has three significant figures 0.0071 m 0.42 m 0.000099 m Each of these measurements has two significant figures 7003 m 40.79 m 1.503 m Each of these measurements has four significant figures 43.00 m 1.010 m 9.000 m Each of these measurements has four significant figures 23 people in the class 60 min = 1 hr 100 cm = 1 m

18. ROUNDING CALCULATIONS • If the digit to the immediate right of the last significant figure is less than five, do not change the last significant figure. example: round the following # to 3 sig figs 1.024 m = 1.02 m • If the digit to the immediate right of the last significant figure is ≥ five, round up the last significant figure. example: round the following # to 3 sig figs 1.025 m = 1.03 m

19. Practice Problems

20. SECTION B.6 RELIABILITY OF MEASUREMENTS • Uncertainty: No measurement is exact because of the limitations of the measuring instrument and because the skill of the person making the measurement. When scientists make measurements, they need to know that it is reliable. There are two ways they can check their work. • PRECISION:One way is to repeat the measurement several times. A reliable measurement will give about the same result again and again under the same conditions. When it does, it is said to be precise, or to have high precision. Poor precision results form poor technique. (b) ACCURACY: The second way of checking a measurement’s reliability is to test it against a standard called an accepted value. A measurement that is close to the accepted value is said to be accurate, or has a high accuracy. Poor accuracy results from procedural or equipment flaws. Reference Table T

22. Density Densities are listed on Table S of your reference tables

23. Practice ProblemsAnswer on a separate piece of paper • CaCl2 is used as a de-icer on roads in the winter. It has a density of 2.50 g/cm3. What is the mass of 15.0 L this substance? • WillominaWitty was assigned to determine the density of a sample of nickel metal. When she finished, she reported the density of nickel as 5.59 g/ml. However, Miraculous knew the density of nickel was 6.44 g/ml what was her percent error?

24. SECTION B.7 REPRESENTING DATA A graph is a visual display of data, which can help to reveal a pattern if one exists. In chemistry, most graphs that you create and interpret will be line graphs. The points on a line graph represent the intersection of data for two variables: the independent and dependent variable.

25. CONSTRUCTION OF A GRAPH • Draw the axes of the graph so that it will fill the paper completely. • Label the axes. The independent variable goes on the x-axis and the dependent variable goes on the y-axis. • Establish a scale for each axis. • Examine the data to determine the highest and lowest values • Assign each division on the axis with an equal value so that all data can be plotted along the axis. Scales divided into multiples of 1, 2, 5, 10, or decimal values are often most convenient. • It is not necessary to start at zero on a scale, nor is it necessary to plot both variables with the same scale. • Plot each pair of measured values. Show each set of data as a point with a small circle drawn around it. • Draw a line that represents the best fit of the data. If the points do not fall in a straight line, draw a smooth curve to represent the “best fit.” In cases where the points do not fall exactly on the line, attempt to have as many data entries represented above the line as below the line. • Write a TITLE above your graph that best represents the information expressed by your graph.

26. INTERPRETATION OF GRAPHS • Identify the independent and dependent variables. Independent Variable: the variable that is changed during an experiment, also called the manipulated variable Dependent Variable: the variable that is observed during an experiment, also called the responding variable

27. INTERPRETATION OF GRAPHS Interpolation: A method of constructing new data points within the range of already known data points Extrapolation: A method of constructing new data points beyond the range of already known data points based on the trend line

28. Practice Problem What is the independent variable? What is the dependent variable? Describe the relationship between the two variables. Using the graph, interpolate or predict the stopping distance at a speed of 20 m/s. Using the graph, extrapolate the line and predict the stopping distance at a speed of 5 m/s. What do you think would happen to the stopping distance at a a speed of 40 m/s Speed (m/s)