Measuring Matter

1. Measuring Matter

2. Measuring Matter in Two Ways Qualitative Measurements: which are usually descriptive like observations. Now it is important to start making… Quantitative Measurements: are in the form of numbers and units.

3. The Powers of Ten • Picture a microscopic cell. • Picture the galaxy.

4. Scientific Notation • Scientists need a way to express extremely LARGE and extremely SMALL numbers in their quantitative measurement. • Scientific notation shows the product of two numbers: A coefficient X 10 to some exponent

5. Scientific Notation Remember that a coefficient is simply a number that you multiply an expression by. **In scientific notation1≤ coefficient <10. Also remember that 10 to some power is simply ten multiplied by itself that many times. Ex. 103 = 10 x 10 x 10 Also, ten to a minus power is dividing by ten that many times.

6. Examples of the use of Scientific Notation • I like to run. For every one mile, I have run 1609 meters. • Expressed in scientific notation, this is 1.609 x 103 meters When you multiply something times ten THREE times, you move the decimal place to the right three times.

7. More examples • The diameter of a human hair is 0.000 008 meters. • Expressed in scientific notation that is, 8.0 x 10-6 meters Note: The negative sign moves the decimal place in the other direction.

8. Try some on your own… 4.57 x 104 9.0 x 10-3 2.42 x 107 6.65 x 10-4 45,700 = 0.009 = 24,200,000 = 0.000665 =

9. Converting to Expanded Form • Move the decimal place the number of times indicated by the exponent. • To the right if it is positive. • To the left if it is negative. Example: 4.5 x 10-2 = 0.045

10. Try some on your own… • 1.2 x 10-4 = • 9.6 x 103 = • 8.07 x 102 = 0.00012 9 600 807

11. Multiplying with Scientific Notation • Multiply the coefficients • Add the exponents Example: (2.0 x 103) x (2.0 x 103) = 4.0 x 106

12. Dividing with Scientific Notation • Divide the coefficients • Subtract the exponent in denominator from the numerator. Example: 3.0 x 104÷ 2.0 x 102 = 1.5 x 104-2 = 1.5 x 102

13. Adding & Subtracting with Scientific Notation • In order to add numbers written in scientific notation, the exponents must match. Example 5.40 x 103 + 6.0 x 102 = Change 6.0 x 102 to 0.60 x 103, then add. 5.40 x 103 + 0.60 x 103 = 6.00 x 103

14. Try some on your own… (3.95 x 102) ÷ (1.5 x 106)  =   (3.5 x 102) (6.45 x 1010) =   (4.44 x 107) ÷ (2.25 x 105)  = (4.50 x 10-12) (3.67 x 10-12) = 2.63 x 10-4 2.2575 x 1013 1.973 x 102 1.6515 x 10-23

15. A Short History of Standard Units Humans did not always have standards by which to measure temperature, time, distance, etc. It was not until 1790 that France established the first metric system.

16. The First Metric System The French established that one meter was one ten-millionth of the distance of the from the Equator to the North Pole. One second was equal to 1/86,400 of the average day.

17. Today’s Standards The techniques used today to establish standards are much more advanced than in 1790… One meter is equal to the distance traveled by light in a vacuum in 1/299,792,458 of a second. One second is defined in terms of the number of cycles of radiation given off by a specific isotope of the element cesium.

18. S.I. Units • The International System of Units is used ALMOST exclusively worldwide (the U.S. is one the of the exceptions). • ALL science is done using S.I. units.

19. The United States’ System of Measurement • In 1975, the U.S. government attempted to adopt the metric system with little success. • The U.S. currently uses the English System of Measurement.

20. Math Quiz Complete the following: • 3 5/6 in. + 8 4/9 in. + 5 2/7 in. =

21. Math Quiz Complete the following: • 3.83 cm + 8.44 cm + 5.29 cm =

22. So why S.I.?

23. So why S.I.? • Decimals are more “computationally friendly” • Multiples of ten • Eliminate LARGE numbers by using prefixes • Scientifically based

24. Measurements and SI Units • Quantitative measurements must include a number AND a unit. • Base units are used with prefixes to indicate fractions or multiples of a unit. • Try to fill in your table.

25. Base Units

26. Prefixes • Prefixes combine with base units to indicate fractions or multiples of a unit.

27. Prefixes

28. SI Prefixes

29. More Details: Length • meters • centimeters (for smaller units of length) • millimeters (very small units of length) • kilometers (for large units of length) These are the most commonly used.

30. More details: Mass • gram • kilogram Measured using balances.

31. More details: Volume • liters • milliliters (for small volumes) • microliter (for extremely small volumes) • Measured using a graduated cylinder, pipet or buret (more accurate), volumetric flask or even a syringe.

32. Volume is a derived units… Some metric units are derived from S.I. units. Volume is L x W x H = cm x cm x cm = cm3 One cm3 is the same as one mL. Also, dm x dm x dm = dm3 One dm3 is the same as one L.

33. Conversions Using Factor Label Method • Multiplying any number by an equality does NOT change the value. • An equality is two measurements that are equal in amount but have different units and numbers. • Examples: one dozen bagels = 12 bagels 10 mm = 1 cm

34. Steps of Factor Label Method • Write down the units you are given. • Write X and a Line. • Write unit you want to cancel on the bottom of the line, the unit you want to keep on the top of the line. Find and plug in your equality. (hint: the larger unit will always get a 1 next to it) • Cancel units and do the math.

35. Let’s do one together… 0.600L = _______mL 1000 mL 0.600L X = 600 mL 1 L 1 L = 1000mL TRY THE REST ON YOUR OWN !!!!

36. Temperature Scales There are three temperature scales in use in this country that you need to be familiar with.

37. Temperature: A measure of the average kinetic energy of the particles in a sample.

38. Fahrenheit • 18th-century German physicist Daniel Gabriel Fahrenheit • Based his scale on an ice-salt mixture and normal body temperature • Freezing point for water = 32°F • Boiling point for water = 212°F

39. Celsius Scale • Swedish guy, Anders Celsius in 174 • Freezing point at 0°C. • Boiling for water at 100°C. • Below 0 is negative.

40. Kelvin Scale • English guy, William Kelvin • Measures molecular movement • Theoretical point of ABSOLUTE ZERO is when all molecular motion stops (no negative numbers) • Divisions (degrees) are the same as in Celsius

41. Absolute Zero • Theoretical point where there is absolutely no movement of molecules in matter and a measure of ZERO ENERGY • This is not something that we ever witness, scientists have only theorized this point

42. Conversion Factors • You need to know these conversion factors! K = °C + 273 °C = K – 273 On Table T NOT on Table T

43. Practice Conversion Problems • Room temperature is approximately 23°C. What is this temperature in Kelvin? • Ethanol has a boiling point of 351 K. That won’t help us if we have a thermometer reading degrees Celsius, so convert it.

44. Uncertainty in Measurement

45. Uncertainty in Measurement • No measurement can be perfect. • Scientists need to account for some degree of uncertainty in measurements. • Refer to terms accuracy and precision. • An ideal measuring device is accurate and precise and does not have a great deal of uncertainty.

46. Accuracy Accuracy is when you are close to the actual value of what you are trying to measure (For example you throw three darts and they are all close to the bull’s eye).

47. Precision Precision is a measure of how close each measurement is to the others. For example if you are at the driving range and all of the golf balls head towards the pond, that is precision (but not accuracy).

49. Uncertainty in Measurement • Uncertainty occurs in every measurement made and must be accounted for. In chemistry, we use different tools, each of which has certain limitations. We use the ± to indicate uncertainty in measurement.

50. Uncertainty Equation • YOU MUST MEMORIZE THIS EQUATION AS YOU WILL PERFORM IT ALMOST DAILY! ΔF = (δF / δX1) ΔX1 + (δF / δX2) ΔX2 + …(δF / δXn) ΔXn