1. Quantitative vs. Qualitative
Make a quantitative observation about your textbook
Make a qualitative observation about your textbook

2. Quantitative vs. Qualitative
Quantitative observation:
Qualitative observation:

3. Precision vs. Accuracy…
Archery Activity

4. Precision vs. Accuracy
Which is more precise for measuring volume, a beaker or a graduated cylinder?

5. Precision vs. Accuracy
Accuracy: refers to the closeness of measurements to the correct or accepted value of the quantity measured.
Precision: refers to the closeness of a set of measurements of the same quantitiy made in the same way.

6. Precision vs. Accuracy
Measured values that are accurate are close to the accepted value
Measured values that are precise are close to one another but not necessarily close to the accepted value

7. Darts within small area = High precision
Area covered on bull’s-eye = High accuracy

8. Darts within small area = High precision
Area far from bull’s-eye = Low accuracy

9. Darts within large area = Low precision
Area far from bull’s-eye = Low accuracy

10. Darts within large area = Low precision
Area centered around bull’s-eye = High accuracy (on average)

11. Unit conversions
Copy metric conversion from book

12. Unit Conversions Practice problems: 750 km = __________m?
283 m = __________km
112 Mwatt = __________Kwatt?
112 Mwatt = __________Gwatt

13. Scientific Notation & Significant Figures

14. Unit Estimation

15. Scientific Notation Used to make numbers more usable
1,000,000,000 = 1x109
=1x10-10

16. How do you figure this out?
You move the decimal until you have only one digit in front of the decimal.
If you move right, then the exponent will be NEGATIVE based on the number of places your decimal moved.
If you move left, then the exponent will be POSITIVE based on the number of places your decimal moved.

17. Practice Give the following in scientific notation 6,289,030,987

18. Give the following in scientific notation…
Practice
6,289,030,987 = = = = = =
x109
x10-3
x102
x10
2.3476x10-1

19. Going the other way… 1.3487x105 = 4.9800456x104 = 2.345x101 =
134,870
49,
23.45
0.3591

20. Try For Yourself 7.234x10-5=? 8.234x103=? 5.000x10-4=? 9.99998x10-2=?

21. ANSWERS
7.234x10-5 =
8.234x103 = 8,234
5.000x10-4 =
x10-2 =
8.555x106 = 8,555,000

22. Significant Digits - What is it?
When we take measurements in science, we can only be sure of our numbers to a certain point
The numbers we are sure of are called significant digits or significant figures (“sig figs”)

23. Sig Figs - How do we use them?
Two types
Measured
You actually measure and record your answer to a certain digit
Calculated
You use already measured numbers to compute an answer

24. Measured Sig Figs Questions you can answer: How long is your book?
Measure it with a meterstick and read the length.
What is the mass of an orange?
Put it on a scale and read the mass.
How much milk is in the carton?
Pour the milk into a graduated cylinder and read the volume.

25. Calculated Sig Figs
Sometimes, you’ve collected the data and you need to calculate a final answer
Example - you find the length, width and height of your book and you want to find the volume.
You need to multiply the three numbers together to get an answer.

26. Determining what counts… Sig Fig Rules!
All non-zero numbers are significant
Example 1,2,3,…,9
All zeros between non-zero numbers are significant
Example
All zeros before a written decimal are significant
Example 600.

27. More Rules…
All zeros following non-zero numbers, after a decimal are significant
Example
These rules are to determine what counts when you are looking at a number.

28. Practice How many sig figs are in the following numbers? 2.341
560
560.

29. Answers
2.341 has 4 sig figs
All the numbers are non-zero digits, so they all count!

30. Answers
has 4 sig figs
The three non-zero numbers 458 and the zero following this set
The first four zeros are place holders - they get the 4 into ten thousands place

31. Answers
Another way to think about having four sig figs is to write it in scientific notation
=4.580x10-4
When you write in scientific notation, you only write the sig figs before you write the x10whatever
So here you see that you wrote the 4, 5, 8, and 0. Those are the sig figs!

32. Answers
560 has 2 sig figs
This one is tricky. Notice that there is no decimal, so the zero is just a place holder to get the 6 into the tens spot.

33. Answers
560. Has 3 sig figs.
This time the zero counts because the decimal means it was actually measured.

34. Answers
has 7 sig figs
All zeros are between non-zero digits, so they are all significant.

35. How do you know when to stop?
When you’re measuring, you know when to stop based on your equipment.
If your equipment reads to the tens, then you can guess up to one more place. You can read to the ones…
Let’s look at it.

36. Multi step calculations
Keep One Extra Digit in Intermediate Answers
When doing multi-step calculations, keep at least one more significant digit in intermediate results than needed in your final answer.
For instance, if a final answer requires two significant digits, then carry at least three significant digits in calculations. If you round-off all your intermediate answers to only two digits, you are discarding the information contained in the third digit, and as a result the second digit in your final answer might be incorrect. (This phenomenon is known as "round-off error.")

37. 2 Greatest Sins in Sig Figs
Writing more digits in an answer (intermediate or final) than justified by the number of digits in the data.
Rounding-off, say, to two digits in an intermediate answer, and then writing three digits in the final answer.

38. Reading the right number of digits.
Ruler/Meterstick
Graduated Cylinder
Beaker
Scale

39. Calculations - The rules!!!
Addition/Subtraction
Your answer should have the same number of decimal places as the number with the least number of decimal places
Multiplication/Division
Your answer should have the same number of sig figs as the number with the least number of sig figs
Always follow the order of operations!
Show two examples of each on the board

40. Practice =
x 3001 =
x 90 = =
900.3/ =
Work out on board - show the number of sig figs for each number before it is operated on.

41. Percent Error
Percent error determines how accurate an experimental value is compared quantitatively with the correct or accepted value.
Percent error: calculated by subtracting the experimental value from the accepted value, dividing the difference by the accepted value, and then multiplying by 100

42. Percent Error
Percent error = Valueaccepted – Valueexperimental x 100 Valueaccepted Percent error can have a positive or negative value

43. Percent Error
A student measures the mass and volume of a substance and calculates its density as 1.40 g/mL. The correct, or accepted value of the density is 1.36 g/mL. What is the percent error of the student’s measurement? = 1.36g/mL – 1.40 g/mL x 100 = -2.9% 1.36 g/mL

44. Percent Error
What is your percent error from the lab when you found the density of water? = 1.00g/mL – g/mL x 100 = -2.9% 1.00 g/mL
Your experimental value

45. Percent Error – pg. 45
Two technicians independently measure the density of a new substance. Technician A Records: 2.000, 1.999, g/mL Technician B Records: 2.5, 2.9, and 2.7 g/mL The correct value is found to be: g/mL. Which Technician is more precise? Which is more accurate? B A

46. Go Through Answers on Packet

47. Directly Proportional
Two quantities are directly proportional if…
Dividing one by the other gives a constant value
y/x = k
k = constant
You can rearrange above equation by saying : y = kx
If one increases…the other increases at the same rate (doubling one constant = doubles the othr
2y/2x = k (constant)

48. Directly Proportional
All directly proportional relationships produce linear graphs that pass through the origin

49. Inverse Proportions Two quantities are inversely proportional if…
Their product is constant
xy = k
k = constant
The greater the speed = less time to travel a given distance
Double speed (2x) = ½ required time
Halving the speed (½) = 2 times the time

50. Inverse Proportional

51. How Sweet It Is Chemistry Lab

52. How Sweet It Is Lab Benedicts Solution Water Bath Test: Results:
Beverages should have tested positive if they had a sugar sweetener
Beverages should test negative if they had an artificial sweetener

53. How Sweet It Is Lab What beverages tested positive?
What beverages tested negative?
Evaluate against labels on Sodas

54. How Sweet It Is Lab
What did you notice about the densities of the solutions?
Which ones had artificial sweeteners? Densities less than one?
Which ones had natural sugar sweeteners? Densities more than one?

55. How Sweet It Is Lab Analysis Questions
1. Evaluate the results against the labels on the soda? Record actual sweeteners on a table in your lab write-up.
How accurate were your results?

56. How Sweet It Is Lab Analysis Questions:
2. Which sample do you think had the highest/lowest sugar content? Explain why you think this.

57. How Sweet It Is Lab Application Questions:
1. How could you prove that carbonated water contains no sweetener?

58. How Sweet It Is Lab Application Questions:
How could you determine a regular/diet soda by using density and not opening the can?
Immerse in water…which one will sink…which one will float?