1. Chapter 2 – Measurements & Calculations

2. Using Scientific Measurements
Table of Contents
Section
Title 1
Scientific Method 2
Units of Measure 3
Using Scientific Measurements

3. Objectives (Section 1) Describe the purpose of the scientific method.
Distinguish between qualitative and quantitative observations.
Describe the differences between hypotheses, theories, and models.

4. The Scientific Method
Science progresses through carefully planned investigation
Scientific Method is a logical approach to solving problems by observing and collecting data, formulating hypotheses, testing hypotheses, and formulating theories that are supported by data.

5. Which chemical is the best penny cleaner?
Which is a better penny cleaner?
1. Ketchup
2. Vinegar
3. Salt

6. Observing & Collecting Data
Observing is the use of the senses to obtain information.
data may be
qualitative (descriptive)
quantitative (numerical)
A system is a specific portion of matter in a given region of space that has been selected for study during an experiment or observation.

7. Qualitative vs. Quantitative Data
Which is a better penny cleaner?
What is the length of this pen?
Which is more subjective? Why?
Which is considered more desirable for science? Why?

8. Formulating Hypotheses
Scientists make generalizations based on the data.
Scientists use generalizations about the data to formulate a hypothesis, or testable statement.
Hypotheses are often “if-then” statements.

9. Testing Hypotheses
Testing a hypothesis requires experimentation that provides data to support or refute a hypothesis or theory.
Controls - experimental conditions that stay constant
Variables - experimental conditions that change

10. Theorizing
A model in science is more than a physical object; it is often an explanation of how phenomena occur and how data or events are related.
visual, verbal, or mathematical
example: atomic model of matter
A theory is a broad generalization that explains a body of facts or phenomena.
example: atomic theory

11. Scientific Method (Visually)

12. Algebra Review

13. Scientific Notation Pages
Converting to Scientific Notation
Move decimal to have one digit (non-zero) to the LEFT
Example: = x 102
Example 2: = 5.2 x 10-1
Decimal to the RIGHT = Negative exponent
Decimal to the LEFT = Positive exponent
Complete pp. 2 #1-5

14. Scientific Notation Pages (2)
Converting from Scientific Notation
Move decimal to a regular value
Example: x 102 = 492
Example 2: x =
Positive exponent = MOVE decimal to the RIGHT
Negative exponent = MOVE decimal to the LEFT
Negative exponents = SMALLER than 1
Complete pp. 2 #1-5

15. Exponent Operations Use the calculator!! Don’t forget the parentheses
Complete pp. 3 #1, 3, 5, & 7

16. Significant Figures & Operations
Use the rules on page 4 + pp. 47 !!
For add/subtract OR multiply/divide, use the rules on page 5 + pp. 49 !!

17. Significant Figures

18. Significant Figs & Operations

19. Section 2.2 – Units of Measurement

20. Lesson Starter
Would you be breaking the speed limit in a 40 mi/hr zone if you were traveling at 60 km/hr?
one kilometer = 0.62 miles

21. Lesson Starter
Would you be breaking the speed limit in a 40 mi/hr zone if you were traveling at 60 km/hr?
one kilometer = 0.62 miles
60 km/h = 37.2 mi/h
You would not be speeding!
km/h and mi/h measure the same quantity using different units

22. Objectives 2.2
Distinguish between a quantity, a unit, and a measurement standard.
Name and use SI units for length, mass, time, volume, and density.
Distinguish between mass and weight.
Perform density calculations.
Transform a statement of equality into conversion factor.

23. Measurement vs. Quantity
Measurements represent quantities.
A quantity is something that has magnitude, size, or amount.
measurement  quantity
the teaspoon is a unit of measurement
volume is a quantity
Measurement = number + unit
The choice of unit depends on the quantity being measured.

24. SI Measurement
Scientists all over the world have agreed on a single measurement system called Le Système International d’Unités, abbreviated SI.
SI has 7 base units
Everything else is DERIVED from these 7 units
Hence, called Derived SI unit

25. SI Base Units

26. 7 Base Units L-MM-TT (Length, Mass, Mole, Time, Temp) Current (A)
Luminous Intensity (cd)

27. SI Prefixes – Need to Know
Symbol
10n
Common
Kilo k
103
Thousand
hecto h
102
Hundred
deca da
101
Ten
100
One or Unit
deci d
10-1
Tenths
centi c
10-2
Hundredth
milli m
10-3
Thousandth

28. SI Prefixes - Extended

29. Converting SI Units
Kilo hecto deca U deci centi milli Complete pages 6 & 7

30. Mass vs. Weight Mass is a measure of the quantity of matter.
Kilogram (kg)
Weight is a measure of the gravitational pull on matter.
Newtons (Don’t need to know units now)
Mass does not depend on gravity.

31. Length Matters Length is a measure of distance.
Meter (m)
Kilometer (km) – longer distances
Centimeter (cm) – shorter distances

32. Derived SI Units Combine more than one SI unit into a new unit
Called derived SI units since they are derived from the 7 SI units

33. Volume Volume is the amount of space occupied by an object.
Cubic meters (m3)
Cubic centimeter (cm3) is often used
Liter (L) is a non-SI unit
1 L = 1000 cm3
1 mL = 1 cm3

34. Density
Density is the ratio of mass to volume, or mass divided by volume.
kg / m3
Can also use: g/mL = g/cm3

36. Conversion Factor
Conversion factor is a ratio derived from the equality between two different units that can be used to convert from one unit to the other.

37. Accuracy & Precision
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 quantity made in the same way.

38. Accuracy & Precision

39. Percentage Error
Percentage error is calculated by subtracting the accepted value from the experimental value, dividing the difference by the accepted value, and then multiplying by 100.

40. Percentage Error Problems
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 1.30 g/mL. What is the percentage error of the student’s measurement?
What is the percentage error for a mass measurement of 17.7g, given the correct value is 21.2g?

41. Percentage Error Problems

42. Section Review & HW Complete Section Review pp. 42 & pp. 57
Complete Practice Problems pp. 59 (#16 – 23)