Chemistry and Manipulating Numerical Data

Measurements Numbers on measurements based on numbers all measurements                                                                                                                                                        Measurements Numbers science is based on measurements all measurements have: - magnitude - uncertainty - units mathematics is based on numbers exact numbers are obtained by: - counting - definition http://antoine.frostburg.edu/chem/senese/101/measurement/slides/sld002.htm

Graphs

shows how many of something Bar Graph shows how many of something are in each category

Unit 1 Test – Honor’s Chemistry Introduction to Chemistry 2nd Hour 5th Hour 6th Hour 8th Hour 1st Hour 55 B’s 27 A’s 35 C’s Avg: 40.9 + 4.0 83.8 + 8.0 % 5 D’s 50 45 40 35 30 This is also about what the quarter grades will look like. September 14, 2007

shows how a whole is broken into parts Pie Graph shows how a whole is broken into parts Percentage of Weekly Income

shows continuous change Line Graph shows continuous change Stock Price over Time

Elements of a “good” line graph axes labeled, with units use the available space title neat Hopefully, students will realize this data makes no sense. As temperature increase – the volume of a gas increases.

How to read a graph 7 L ~4 L Interpolate - read between data points What volume would the gas occupy at a temperature of 150 K? Extrapolate - read data beyond data points What volume would the gas occupy at a temperature of 260 K? Which do you have more confidence in? Why? 7 L (dependent variable) Hopefully, students will realize this data makes no sense. As temperature increase – the volume of a gas increases. ~4 L (independent variable)

Graphs Line Graph Bar Graph Pie Graph Used to show trends or continuous change Bar Graph Used to display information collected by counting Pie Graph Used to show how some fixed quantity is broken down into parts GRAPHS Each graph is used for a specific reason.

Line Graph A B C D How does the mass of a penny change with age? Mass (g) Mass (g) Age (Year of Penny) Age (Year of Penny) C D LINE GRAPH Interpolate – estimate a value between data points on graph. Extrapolate – estimate a value beyond collected data points. Either before or after. **We have less confidence in data extrapolated than interpolated. In graph A: all pennies have the same mass (a reasonable hypothesis) - WRONG Graph B: older pennies have more mass (this may be due to the fact the pick up mass as they get dirty) - WRONG Graph C: older pennies have less mass (this may be caused by pennies wearing out in circulation) – WRONG Graph D: correct; pennies before 1982 were made of solid copper, and pennies after 1982 were made of a zinc core and a thin copper coating Mass (g) Mass (g) Age (Year of Penny) Age (Year of Penny)

Bar Graph Chemistry Grades Descriptive title Legend Number of Students Axis labeled (with units)

Pie Graph Note on graph of Earth’s crust that the majority of elements making up the Earth’s crust is oxygen and silicon. This is because they Earth is covered with sand (silicon dioxide (SiO2)). Aluminum composes a tremendous 7.5% of the Earth’s crust. Why recycle aluminum? It takes less energy (resources) to recycle aluminum than mine its ore and refine the ore to extract aluminum . Bottom line – it is cheaper to recycle the aluminum already mined from the Earth’s crust.

Pie Graphs

Reviewing Concepts Presenting Scientific Data How do scientists organize data? How can scientists communicate experimental results? What does a given point represent on a line graph? The density of copper is 8.92 g/cm3. If you plotted the volume in cubic centimeters, what would the slope of the line be? Prentice Hall Physical Science Concepts in Action (Wysession, Frank, Yancopoulos) 2004 pg 25 Scientists can organize their data by using data tables and graphs. Scientists can communicate results by writing in journals or speaking at conferences.