 # CHEMISTRY Matter and Change

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CHEMISTRY Matter and Change
Chapter 2: Analyzing Data

CHAPTER2 Table Of Contents Section 2.1 Units and Measurements Section 2.2 Scientific Notation and Dimensional Analysis Section 2.3 Uncertainty in Data Section 2.4 Representing Data Click a hyperlink to view the corresponding slides. Exit

Units and Measurements
SECTION2.1 Units and Measurements Define SI base units for time, length, mass, and temperature. Explain how adding a prefix changes a unit. Compare the derived units for volume and density. mass: a measurement that reflects the amount of matter an object contains

Units and Measurements
SECTION2.1 Units and Measurements base unit second meter kilogram kelvin derived unit liter density Chemists use an internationally recognized system of units to communicate their findings.

Units and Measurements
SECTION2.1 Units and Measurements Units Système Internationale d'Unités (SI) is an internationally agreed upon system of measurements. A base unit is a defined unit in a system of measurement that is based on an object or event in the physical world, and is independent of other units.

Units and Measurements Units and Measurements
SECTION2.1 SECTION2.1 Units and Measurements Units and Measurements Units (cont.)

Units and Measurements
SECTION2.1 Units and Measurements Units (cont.)

Units and Measurements
SECTION2.1 Units and Measurements Units (cont.) The SI base unit of time is the second (s), based on the frequency of radiation given off by a cesium-133 atom. The SI base unit for length is the meter (m), the distance light travels in a vacuum in 1/299,792,458th of a second. The SI base unit of mass is the kilogram (kg), about 2.2 pounds

Units and Measurements
SECTION2.1 Units and Measurements Units (cont.) The SI base unit of temperature is the kelvin (K). Zero kelvin is the point where there is virtually no particle motion or kinetic energy, also known as absolute zero. Two other temperature scales are Celsius and Fahrenheit.

Units and Measurements
SECTION2.1 Units and Measurements Derived Units Not all quantities can be measured with SI base units. A unit that is defined by a combination of base units is called a derived unit.

Units and Measurements
SECTION2.1 Units and Measurements Derived Units (cont.) Volume is measured in cubic meters (m3), but this is very large. A more convenient measure is the liter, or one cubic decimeter (dm3).

Units and Measurements
SECTION2.1 Units and Measurements Derived Units (cont.) Density is a derived unit, g/cm3, the amount of mass per unit volume. The density equation is density = mass/volume.

Which of the following is a derived unit?
SECTION2.1 Section Check Which of the following is a derived unit? A. yard B. second C. liter D. kilogram

What is the relationship between mass and volume called?
SECTION2.1 Section Check What is the relationship between mass and volume called? A. density B. space C. matter D. weight

Scientific Notation and Dimensional Analysis
SECTION2.2 Scientific Notation and Dimensional Analysis Express numbers in scientific notation. Convert between units using dimensional analysis. quantitative data: numerical information describing how much, how little, how big, how tall, how fast, and so on

Scientific Notation and Dimensional Analysis
SECTION2.2 Scientific Notation and Dimensional Analysis scientific notation dimensional analysis conversion factor Scientists often express numbers in scientific notation and solve problems using dimensional analysis.

Scientific Notation and Dimensional Analysis
SECTION2.2 Scientific Notation and Dimensional Analysis Scientific Notation Scientific notation can be used to express any number as a number between 1 and 10 (known as the coefficient) multiplied by 10 raised to a power (known as the exponent). Carbon atoms in the Hope Diamond = 4.6 x 1023 4.6 is the coefficient and 23 is the exponent.

Scientific Notation and Dimensional Analysis
SECTION2.2 Scientific Notation and Dimensional Analysis Scientific Notation (cont.) Count the number of places the decimal point must be moved to give a coefficient between 1 and 10. The number of places moved equals the value of the exponent. The exponent is positive when the decimal moves to the left and negative when the decimal moves to the right. 800 = 8.0  102 = 3.43  10–5

Scientific Notation and Dimensional Analysis
SECTION2.2 Scientific Notation and Dimensional Analysis Scientific Notation (cont.) Addition and subtraction Exponents must be the same. Rewrite values to make exponents the same. Ex x x 1017, you must rewrite one of these numbers so their exponents are the same. Remember that moving the decimal to the right or left changes the exponent. 2.840 x x 1018 Add or subtract coefficients. Ex x x 1017 = 3.2 x 1018

Scientific Notation and Dimensional Analysis
SECTION2.2 Scientific Notation and Dimensional Analysis Scientific Notation (cont.) Multiplication and division To multiply, multiply the coefficients, then add the exponents. Ex. (4.6 x 1023)(2 x 10-23) = 9.2 x 100 To divide, divide the coefficients, then subtract the exponent of the divisor from the exponent of the dividend. Ex. (9 x 107) ÷ (3 x 10-3) = 3 x 1010 Note: Any number raised to a power of 0 is equal to 1: thus, 9.2 x 100 is equal to 9.2.

Scientific Notation and Dimensional Analysis
SECTION2.2 Scientific Notation and Dimensional Analysis Dimensional Analysis Dimensional analysis is a systematic approach to problem solving that uses conversion factors to move, or convert, from one unit to another. A conversion factor is a ratio of equivalent values having different units.

Scientific Notation and Dimensional Analysis
SECTION2.2 Scientific Notation and Dimensional Analysis Dimensional Analysis (cont.) Writing conversion factors Conversion factors are derived from equality relationships, such as 1 dozen eggs = 12 eggs. Percentages can also be used as conversion factors. They relate the number of parts of one component to 100 total parts.

Scientific Notation and Dimensional Analysis
SECTION2.2 Scientific Notation and Dimensional Analysis Dimensional Analysis (cont.) Using conversion factors A conversion factor must cancel one unit and introduce a new one.

SECTION2.2 Section Check What is a systematic approach to problem solving that converts from one unit to another? A. conversion ratio B. conversion factor C. scientific notation D. dimensional analysis

SECTION2.2 Section Check Which of the following expresses 9,640,000 in the correct scientific notation? A  104 B  105 C × 106 D  610

Uncertainty in Data Define and compare accuracy and precision.
SECTION2.3 Uncertainty in Data Define and compare accuracy and precision. Describe the accuracy of experimental data using error and percent error. Apply rules for significant figures to express uncertainty in measured and calculated values. experiment: a set of controlled observations that test a hypothesis

Uncertainty in Data accuracy precision error percent error
SECTION2.3 Uncertainty in Data accuracy precision error percent error significant figures Measurements contain uncertainties that affect how a result is presented.

Accuracy and Precision
SECTION2.3 Uncertainty in Data Accuracy and Precision Accuracy refers to how close a measured value is to an accepted value. Precision refers to how close a series of measurements are to one another.

Accuracy and Precision (cont.)
SECTION2.3 Uncertainty in Data Accuracy and Precision (cont.) Error is defined as the difference between an experimental value and an accepted value.

Accuracy and Precision (cont.)
SECTION2.3 Uncertainty in Data Accuracy and Precision (cont.) The error equation is error = experimental value – accepted value. Percent error expresses error as a percentage of the accepted value.

Uncertainty in Data Significant Figures
SECTION2.3 Uncertainty in Data Significant Figures Often, precision is limited by the tools available. Significant figures include all known digits plus one estimated digit.

Significant Figures (cont.)
SECTION2.3 Uncertainty in Data Significant Figures (cont.) Rules for significant figures Rule 1: Nonzero numbers are always significant. Rule 2: Zeros between nonzero numbers are always significant. Rule 3: All final zeros to the right of the decimal are significant. Rule 4: Placeholder zeros are not significant. To remove placeholder zeros, rewrite the number in scientific notation. Rule 5: Counting numbers and defined constants have an infinite number of significant figures.

Uncertainty in Data Rounding Numbers
SECTION2.3 Uncertainty in Data Rounding Numbers Calculators are not aware of significant figures. Answers should not have more significant figures than the original data with the fewest figures, and should be rounded.

Rounding Numbers (cont.)
SECTION2.3 Uncertainty in Data Rounding Numbers (cont.) Rules for rounding Rule 1: If the digit to the right of the last significant figure is less than 5, do not change the last significant figure. Rule 2: If the digit to the right of the last significant figure is greater than 5, round up the last significant figure. Rule 3: If the digits to the right of the last significant figure are a 5 followed by a nonzero digit, round up the last significant figure.

Rounding Numbers (cont.)
SECTION2.3 Uncertainty in Data Rounding Numbers (cont.) Rules for rounding (cont.) Rule 4: If the digits to the right of the last significant figure are a 5 followed by a 0 or no other number at all, look at the last significant figure. If it is odd, round it up; if it is even, do not round up.

Rounding Numbers (cont.)
SECTION2.3 Uncertainty in Data Rounding Numbers (cont.) Addition and subtraction Round the answer to the same number of decimal places as the original measurement with the fewest decimal places. Multiplication and division Round the answer to the same number of significant figures as the original measurement with the fewest significant figures.

SECTION2.3 Section Check Determine the number of significant figures in the following: 8,200, 723.0, and 0.01. A. 4, 4, and 3 B. 4, 3, and 3 C. 2, 3, and 1 D. 2, 4, and 1

SECTION2.3 Section Check A substance has an accepted density of 2.00 g/L. You measured the density as 1.80 g/L. What is the percent error? A. 20% B. –20% C. 10% D. 90%

Representing Data Create graphics to reveal patterns in data.
SECTION2.4 Representing Data Create graphics to reveal patterns in data. independent variable: the variable that is changed during an experiment Interpret graphs. graph Graphs visually depict data, making it easier to see patterns and trends.

Representing Data Graphing
SECTION2.4 Representing Data Graphing A graph is a visual display of data that makes trends easier to see than in a table.

Representing Data Graphing (cont.)
SECTION2.4 Representing Data Graphing (cont.) A circle graph, or pie chart, has wedges that visually represent percentages of a fixed whole.

Representing Data Graphing (cont.)
SECTION2.4 Representing Data Graphing (cont.) Bar graphs are often used to show how a quantity varies across categories.

Representing Data Graphing (cont.)
SECTION2.4 Representing Data Graphing (cont.) On line graphs, independent variables are plotted on the x-axis and dependent variables are plotted on the y-axis.

Representing Data Graphing (cont.)
SECTION2.4 Representing Data Graphing (cont.) If a line through the points is straight, the relationship is linear and can be analyzed further by examining the slope.

Representing Data Interpreting Graphs
SECTION2.4 Representing Data Interpreting Graphs Interpolation is reading and estimating values falling between points on the graph. Extrapolation is estimating values outside the points by extending the line.

Interpreting Graphs (cont.)
SECTION2.4 Representing Data Interpreting Graphs (cont.) This graph shows important ozone measurements and helps the viewer visualize a trend from two different time periods.

____ variables are plotted on the ____-axis in a line graph.
SECTION2.4 Section Check ____ variables are plotted on the ____-axis in a line graph. A. independent, x B. independent, y C. dependent, x D. dependent, z

What kind of graph shows how quantities vary across categories?
SECTION2.4 Section Check What kind of graph shows how quantities vary across categories? A. pie charts B. line graphs C. Venn diagrams D. bar graphs

Analyzing Data Chemistry Online Study Guide Chapter Assessment
Resources Chemistry Online Study Guide Chapter Assessment Standardized Test Practice

Units and Measurements
SECTION2.1 Units and Measurements Study Guide Key Concepts SI measurement units allow scientists to report data to other scientists. Adding prefixes to SI units extends the range of possible measurements. To convert to Kelvin temperature, add 273 to the Celsius temperature. K = °C + 273 Volume and density have derived units. Density, which is a ratio of mass to volume, can be used to identify an unknown sample of matter.

Scientific Notation and Dimensional Analysis
SECTION2.2 Scientific Notation and Dimensional Analysis Study Guide Key Concepts A number expressed in scientific notation is written as a coefficient between 1 and 10 multiplied by 10 raised to a power. To add or subtract numbers in scientific notation, the numbers must have the same exponent. To multiply or divide numbers in scientific notation, multiply or divide the coefficients and then add or subtract the exponents, respectively. Dimensional analysis uses conversion factors to solve problems.

Uncertainty in Data Key Concepts
SECTION2.3 Uncertainty in Data Study Guide Key Concepts An accurate measurement is close to the accepted value. A set of precise measurements shows little variation. The measurement device determines the degree of precision possible. Error is the difference between the measured value and the accepted value. Percent error gives the percent deviation from the accepted value. error = experimental value – accepted value

Uncertainty in Data Key Concepts
SECTION2.3 Uncertainty in Data Study Guide Key Concepts The number of significant figures reflects the precision of reported data. Calculations should be rounded to the correct number of significant figures.

Representing Data Key Concepts
SECTION2.4 Representing Data Study Guide Key Concepts Circle graphs show parts of a whole. Bar graphs show how a factor varies with time, location, or temperature. Independent (x-axis) variables and dependent (y-axis) variables can be related in a linear or a nonlinear manner. The slope of a straight line is defined as rise/run, or ∆y/∆x. Because line graph data are considered continuous, you can interpolate between data points or extrapolate beyond them.

CHAPTER2 Analyzing Data Chapter Assessment Which of the following is the SI derived unit of volume? A. gallon B. quart C. m3 D. kilogram

Analyzing Data Which prefix means 1/10th? A. deci- B. hemi- C. kilo-
CHAPTER2 Analyzing Data Chapter Assessment Which prefix means 1/10th? A. deci- B. hemi- C. kilo- D. centi-

Analyzing Data Divide 6.0  109 by 1.5  103. A. 4.0  106
CHAPTER2 Analyzing Data Chapter Assessment Divide 6.0  109 by 1.5  103. A. 4.0  106 B. 4.5  103 C. 4.0  103 D. 4.5  106

Analyzing Data Round 2.3450 to 3 significant figures. A. 2.35 B. 2.345
CHAPTER2 Analyzing Data Chapter Assessment Round to 3 significant figures. A. 2.35 B C. 2.34 D. 2.40

CHAPTER2 Analyzing Data Chapter Assessment The rise divided by the run on a line graph is the ____. A. x-axis B. slope C. y-axis D. y-intercept

Analyzing Data Which is NOT an SI base unit? A. meter B. second
CHAPTER2 Analyzing Data Chapter Assessment Which is NOT an SI base unit? A. meter B. second C. liter D. kelvin

Analyzing Data Which value is NOT equivalent to the others? A. 800 m
CHAPTER2 Analyzing Data Standardized Test Practice Which value is NOT equivalent to the others? A. 800 m B. 0.8 km C. 80 dm D. 8.0 x 104 cm

CHAPTER2 Analyzing Data Standardized Test Practice Find the solution with the correct number of significant figures: 25  0.25 A. 6.25 B. 6.2 C. 6.3 D

CHAPTER2 Analyzing Data Standardized Test Practice How many significant figures are there in meters? A. 4 B. 5 C. 6 D. 11

Analyzing Data Which is NOT a quantitative measurement of a liquid?
CHAPTER2 Analyzing Data Standardized Test Practice Which is NOT a quantitative measurement of a liquid? A. color B. volume C. mass D. density

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