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# Chem unit 1 presentation

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### Chem unit 1 presentation

1. 1. What is data and what can it tell us?<br />Chemistry: Unit 1<br />
2. 2. What is data?<br />
3. 3. What can data tell us?<br />
4. 4. Skills<br /><ul><li>Metric Conversions
5. 5. Dimensional Analysis
6. 6. Graphing
7. 7. Scientific Notation
8. 8. Data Pattern Recognition
9. 9. Calculations with Significant Figures</li></li></ul><li>1:1 Units and Measurements<br />Goals and Objectives:<br />Define SI base units for time, length, mass, and temperature.<br />Explain how adding a prefix changes a unit.<br />Compare the derived units for volume and density.<br />
10. 10. Units and Measurements<br />Base unit – is a defined unit in a system of measurement that is based on an object.<br />
11. 11. SI Units<br />
12. 12. Prefixes<br />Objective: Explain how adding a prefix changes a unit.<br />How important are prefixes?<br />
13. 13. SI Unit Prefixes<br />
14. 14. Units and Measurements<br />Kelvin – The SI unit for temperature. Based on Absolute Zero.<br />Kelvin – Celsius Conversion Equation<br />K = °C + 273<br />
15. 15. Derived Unit<br />Derived unit – a unit that is defined by a combination of base units.<br />Examples:<br />g/ml<br />cm3<br />m/s2<br />
16. 16. Derived Unit<br />Liter – the SI unit for volume.<br />1L = dm3<br />1ml = 1cm3<br />
17. 17. Density<br />Density – is a physical property of matter and is defined a s the amount of mass per unit volume.<br />D = m/v<br />
18. 18. Practice Problems<br />CALM: Unit 1:1<br />End 1:1<br />
19. 19. 1:2 Scientific Notation<br />Goals and Objectives:<br />Express numbers in scientific notation.<br />Convert between units using dimensional analysis.<br />
20. 20. Scientific Notation<br />Scientific notation – a method that conveniently restates a number without changing its value.<br />Coefficient – is the first number in scientific notation. (1-10)<br />Exponent – the multiplier of the coefficient by the power of 10.<br />
21. 21. Scientific Notation<br />Example<br />
22. 22. Adding and Subtracting Scientific Notation<br />Exponents must be the same. Convert if necessary.<br />Coefficients are added or subtracted.<br />Change exponent to simplify answer.<br />
23. 23. Adding and Subtracting Scientific Notation<br />Example<br />
24. 24. Multiplication and Division using Scientific Notation<br />Exponents do not need to be the same.<br />Multiply or divide coefficients<br />When multiplying, add exponents<br />When dividing, subtract exponents. (divisor from dividend)<br />
25. 25. Multiplication and Division using Scientific Notation<br />Example<br />
26. 26. Dimensional Analysis<br />Dimensional Analysis – is a systematic approach to problem solving that uses conversion factors to move, or convert, from one unit to another.<br />Example<br />
27. 27. Conversion Factor<br />Conversion Factor - Is a ratio of equivalent values having different units.<br />Examples:<br />1000m / 1km<br />1 hr / 3600s<br /> 1 ml / 1 cm3<br />
28. 28. Practice Problems<br />CALM: Unit 1:2<br />End 1:2<br />
29. 29. 1:3 Uncertainty in Data<br />Goals and Objectives:<br />Define and compare accuracy and precision.<br />Describe the accuracy of experimental data using error and percent error<br />Apply rules for significant figures to express uncertainty in measured and calculated values.<br />
30. 30. Uncertainty in Data<br />Accuracy – is how close a measure value is to an accepted value.<br />Precision - Is how close a series of measurements are to one another. <br />The amount of uncertainty in a measurement<br />More precise = less uncertainty<br />
31. 31. Precision in Measurements<br />When measuring any item, write all digits that are confirmed and one estimated digit.<br />Example<br />
32. 32. Error<br />Error is the difference between an experimental value and an accepted value.<br />Error = experimental value – accepted value<br />Example<br />
33. 33. Percent Error<br />Percent error expresses error as a percentage of the accepted value<br />Percent error = <br />
34. 34. Significant Figures<br />Rules for Significant Digits<br />Nonzero digits are always significant.<br />Zeroes are sometimes significant, and sometimes they are not.<br />Zeroes at the beginning of a number (used just to position the decimal point) are never significant.<br />Zeroes between nonzero digits are always significant.<br />Zeroes at the end of a number that contains a decimal point are always significant.<br />Zeroes at the end of a number that does not contain a decimal point may or may not be significant.<br />Scientific notation is used to clarify these numbers.<br />
35. 35. Significant Figures<br />Rules for Significant Digits<br />Exact numbers can be considered as having an unlimited number of significant figures. <br />In addition and subtraction, the number of significant digits in the answer is determined by the least precise number in the calculation.<br />The number of significant figures to the right of the decimal in the answer cannot exceed any of those in the calculation.<br />In multiplication and division, the answer cannot have more significant digits than any number in the calculation. <br />
36. 36. Significant Figures<br />Examples<br />
37. 37. Rounding Numbers<br />When rounding numbers to the proper number of significant digits, look to the right of the last significant digit. <br />1-4: round down the last sig fig<br />5-9: round up the last sig fig.<br />
38. 38. Rounding Numbers<br />Examples:<br />54.3654 to 4 sig figs:<br />To 3 sig figs:<br />To 2 sig figs:<br />To 1 sig fig:<br />
39. 39. Practice Problems<br />CALM: 1:3<br />
40. 40. 1:4 Representing Data<br />Goals and Objectives<br />Create graphs to reveal patterns in data.<br />Interpret graphs.<br />Explain how chemists describe submicroscopic matter.<br />
41. 41. Representation of Data<br />Graph is a visual display of data<br />Circle graphs (pie chart) – display parts of a whole.<br />Bar graphs – shows how a quantity varies across categories<br />Line graphs – most graphs used in chemistry<br />
42. 42. Rules for Good Graphing<br />Rules for Good Graphing on Paper:<br />All graphs should be on graph paper. <br />Identify the independent and dependent variables in your data.<br />The independent variable is plotted on the horizontal axis (x-axis) and the dependent variable is plotted on the vertical axis (y-axis).<br />Determine the range of the independent variable to be plotted. <br />Spread the data out as much as possible. Let each division on the graph paper stand for a convenient unit. This usually means units that are multiples of 2, 5 or 10…etc. <br />
43. 43. Rules for Good Graphing<br />Rules for Good Graphing on Paper:<br />Number and label the horizontal axis. The label should include units.<br />Repeat steps 2. through 4. for the dependent variable.<br />Plot the data points on the graph.<br />Draw the best-fit straight or smooth curve line that passes through as many points as possible. Do not use a series of straight-line segments to connect the dots. <br />Give the graph a title that clearly tells what the graph represents (y vs. x values).<br />
44. 44. Rules for Good Graphing<br />Rules for Good Graphing on the Computer:<br />From the insert menu on the Microsoft word program choose insert chart.<br />Identify the independent and dependent variables in your data.<br />The independent variable is plotted on the horizontal axis (x-axis) and the dependent variable is plotted on the vertical axis (y-axis).<br />Insert data in the excel window that opens. Be sure to pay attention to the excel column vs. graph axes location.<br />Through the toolbox menu, give the graph a title that clearly tells what the graph represents. (y vs. x variable). <br />Through the toolbox menu, give the axes in the graph labels that include units. <br />
45. 45. Representing Data<br />Linear relationship – variables are proportionally related<br />Line of best-fit is a straight line but is not perfectly horizontal or vertical.<br />
46. 46. Representing Data<br />Slope – is equal to the change in y divided by the change in x<br />Rise/run<br />Δy/Δx<br />
47. 47. Representing Data<br />Interpolation – the reading of a value from any point that falls between recorded data points<br />When points on a line graph are connected, the data is considered to be continuous.<br />
48. 48. Representing Data<br />Extrapolation – the process of estimating values beyond the plotted points.<br />The line of best fit is extended beyond the scope of the data<br />
49. 49. Representing Data<br />Model – is a visual, verbal or mathematical explanation of experimental data. <br />Example<br />
50. 50. Practice Problems<br />No homework<br />End 1:4<br />
51. 51. 1:5 Scientific Method and Research<br />Goals and Objectives<br />Identify the common steps of scientific methods.<br />Compare and contrast types of data.<br />Identify types of variables.<br />Describe the difference between a theory and a scientific law.<br />Compare and contrast pure research, applied research, and technology<br />
52. 52. Scientific Method and Research<br />Scientific Method – is a systematic approach and organized process used in scientific study to do research<br />Observation<br />Hypothesis<br />Experiments<br />Conclusion<br />
53. 53. Scientific Method<br />Observation – is an act of gathering information.<br />Qualitative – information that describes color, odor, shape or other physical characteristic<br />Quantitative – information taken in the form of a measurement.<br />Temperature, pressure, volume, quantity, mass<br />
54. 54. Scientific Method<br />Hypothesis – is a tentative explanation for what has been observed. <br />
55. 55. Scientific Method<br />Experiments – is a set of controlled observations that test the hypothesis.<br />Independent variable – the variable that is controlled or changed incrementally.<br />Dependent variable – the value that changes in response to the independent variable. <br />Control – is a standard for comparison.<br />
56. 56. Scientific Method<br />Conclusion – is a judgment based on the information obtained. <br />
57. 57. Scientific Method<br />
58. 58. Scientific Theory and Law<br />Theory – is an explanation of a natural phenomenon based on many observations and investigations over time. <br />Scientific Law- a relationship in nature that is supported by many experiments. <br />
59. 59. Scientific Research<br />Pure research – is done to gain knowledge for the sake of knowledge itself.<br />Applied research – is research undertaken to solve a specific problem <br />
60. 60. Practice Problems<br />CALM: 1:5<br />
61. 61. What is data?<br />
62. 62. What can data tell us?<br />
63. 63. The END<br />