Respond in writing to the following quote:

1. Respond in writing to the following quote: “"The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I found it!) but 'That's funny...' "

2. 2.1 Real Scientific Methods Is there really just one scientific method?

3. Scientific Methods • techniques used in science to discovery new knowledge, create new inventions, etc. • there are many different ways- and many of them are not structured procedures • Scientists must be great observers and very creative but also be prepared to make connections between what they know and what they see

4. Making Observations 2 types of info: • Quantitative-numerical (usually numbers) • Qualitative- descriptive (usually words) • System- what you are studying

5. Testing Ideas • Figure out whether it is true or not • Use experiments • Can kind of ideas can we test?

6. 2.2 Units of Measurement

7. Measurement • Quantitative information • Need a number and a unit (most of time) • Represents a quantity • For example: 2 meters • 2 is number • Meters is unit • Length is quantity • Units compare what is being measured to a defined measurement standard

8. SI Measurement • Le Systeme International d’Unites : SI • System of measurement agreed on all over the world in 1960 • Contains 7 base units • units are defined in terms of standards of measurement that are objects or natural occurrence that are of constant value or are easily reproducible • We still use some non-SI units

9. Important SI Base Units

10. Prefixes • Prefixes are added to the base unit names to represent quantities smaller or larger

11. Mass • Measure of the quantity of matter • SI unit: kg • use g a lot too • mass vs. weight • weight is the measure of gravitational pull on matter • mass does not depend on gravity • on a new planet, mass would be same but weight could change

12. Length • SI unit: m • use cm a lot too • km is used instead of miles for highway distances and car speeds in most countries

13. Derived SI Units • come from combining base units • combine using multiplication or division Example: Area: A = length x width = m x m = m2

14. Volume • amount of space occupied by object • SI: m3 = m x m x m • use cm3 in lab a lot • non-SI: 1 liter = 1000cm3 = 1000mL

15. ratio of mass to volume SI: Density • characteristic property of substance (doesn’t change with amount ) because as volume increases, mass also increases • density usually decreases as T increases • exception: ice is less dense than liquid water so it floats

16. Example A sample of aluminum metal has a mass of 8.4 g. The volume is 3.1 cm3. Find the density.

17. Conversion Factors • ratio that comes from a statement of equality between 2 different units • every conversion factor is equal to 1 Example: statement of equality conversion factor

18. Conversion Factors • can be multiplied by other numbers without changing the value of the number • since you are just multiplying by 1

19. Guidelines for Conversions • always consider what unit you are starting and ending with • if you aren’t sure what steps to take, write down all the info you know about the start and end unit to find a connection • always begin with the number and unit you are given with a 1 below it • always cancel units as you go • the larger unit in the conversion factor should usually have a one next to it

20. Example 1 Convert 5.2 cm to mm • Known: 100 cm = 1 m 1000 mm = 1 m • Must use m as an intermediate

21. Example 2 Convert 0.020 kg to mg • Known: 1 kg = 1000 g 1000 mg = 1 g • Must use g as an intermediate

22. Example 3 Convert 500,000 μg to kg • Known: 1,000,000 μg = 1 g 1 kg = 1000 g • Must use g as an intermediate

23. Advanced Conversions • One difficult type of conversion deals with squared or cubed units • Be sure to square or cube the conversion factor you are using to cancel all the units • If you tend to forget to square or cube the number in the conversion factor, try rewriting the conversion factor instead of just using the exponent

24. Example • Convert: 2000 cm3 to m3 • No intermediate needed Known: 100 cm = 1 m cm3 = cm x cm x cm m3 = m x m x m OR

25. Advanced Conversions • Another difficult type of conversion deals units that are fractions themselves • Be sure convert one unit at a time; don’t try to do both at once • Work on the unit on top first; then work on the unit on the bottom • Setup your work the exact same way

26. Example Known: 1000 g = 1 kg 1000 mL = 1 L • Convert: 350 g/mL to kg/L • No intermediate needed OR

27. Combination Example • Convert: 7634 mg/m3 to Mg/L Known: 100 cm = 1 m 1000 mg = 1 g 1 cm3 = 1 mL 1,000,000 g = 1 Mg 1000 mL = 1 L

28. 2.3 Using Scientific Measurements

29. Accuracy vs. Precision • Accuracy- closeness of measurement to correct or accepted value • Precision- closeness of a set of measurements

30. Accuracy vs. Precision

31. Percent Error vs. Percent Difference • Percent Error: • Measures the accuracy of an experiment • Can have + or – value

32. Example • Measured density from lab experiment is 1.40 g/mL. The correct density is 1.36 g/mL. • Find the percent error.

33. Significant Figures • All certain digits plus one estimated digit

34. Determining Number of Sig Figs • All non-zero numbers are sig figs • Zeros depend on location in number: LEADING zeros never count EMBEDDED zeros always count TRAILING zeros only count if there is a point.

35. Location of Zeros • EMBEDDED: between non-zero numbers • All are sig figs • LEADING: at front of all non-zero numbers • None are sig figs • TRAILING: at the end of non-zero numbers • If there is a decimal, all are sig figs • If there is not, none are sig figs

36. Practice 101.02 IMBEDDED 5 20.0 TRAILING w/ 3 0.005302 LEADING 4 17000 TRAILING w/o 2 4320. TRAILING w/ 4

37. Rounding • Need to use rounding to write a calculation correctly • Calculator gives you lots of insignificant figures and you must round to the right place • When rounding, look at the digit after the one you can keep • Greater than or equal to 5, round up • Less than 5, keep the same

38. Examples Make the following have 3 sig figs: • 761.50  762 • 14.334  14.3 • 10.44  10.4 • 10789  10800 • 8024.50  8020 • 203.514  204

39. Using Sig Figs in Calculations • Adding/Subtracting: • end with the least number of decimal places

40. Using Sig Figs in Calculations • Adding/Subtracting: • end with the least number of decimal places

41. Using Sig Figs in Calculations • Multiplying/Dividing: • end with the least number of sig figs

42. Using Sig Figs in Calculations • Multiplying/Dividing: • end with the least number of sig figs