chem unit 1 presentation

What is data and what can it tell us?

Chemistry: Unit 1

What is data?

What can data tell us?

SkillsMetric ConversionsDimensional AnalysisGraphingScientific NotationData Pattern RecognitionCalculations with Significant

Figures

1:1 Units and Measurements

Goals and Objectives:• 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.

Units and Measurements

Base unit – is a defined unit in a system of measurement that is based on an object.

SI Units

Base Quantity

Base Unit Symbol

Length Meter mMass Kilogram/gram kgTime Second STemperature Kelvin KAmount of a Substance

Mole mol

Electric Current Ampere ALuminous Intensity

Candela cd

Prefixes

Objective: Explain how adding a prefix changes a unit.

How important are prefixes?

SI Unit PrefixesPrefixes Symbol Decimal Sc.Notati

onFemto- f .000 000 000 000

001

10-15

Pico- p .000 000 000 001 10-12

Nano- n .000 000 001 10-9

Micro- µ .000 001 10-6

Milli m .001 10-3

Centi c .01 10-2

Deci- d .1 10-1

Kilo- k 1 000 103

Mega M 1 000 000 106

Giga G 1 000 000 000 109

Tera T 1 000 000 000 000 1012

Units and Measurements

Kelvin – The SI unit for temperature. Based on Absolute Zero.

• Kelvin – Celsius Conversion Equation• K = °C + 273

Derived Unit

Derived unit – a unit that is defined by a combination of base units.• Examples:

• g/ml• cm3

• m/s2

Derived Unit• Liter – the SI unit for volume.

• 1L = dm3

• 1ml = 1cm3

Density• Density – is a physical property

of matter and is defined a s the amount of mass per unit volume.• D = m/v

Practice Problems• CALM: Unit 1:1

End 1:1

1:2 Scientific Notation

Goals and Objectives:• Express numbers in scientific

notation.• Convert between units using

dimensional analysis.

Scientific Notation

Scientific notation – a method that conveniently restates a number without changing its value.

• Coefficient – is the first number in scientific notation. (1-10)

• Exponent – the multiplier of the coefficient by the power of 10.

Scientific Notation• Example

Adding and Subtracting Scientific Notation

• Exponents must be the same. Convert if necessary.

• Coefficients are added or subtracted.

• Change exponent to simplify answer.

Adding and Subtracting Scientific NotationExample

Multiplication and Division using Scientific Notation

• Exponents do not need to be the same.

• Multiply or divide coefficients• When multiplying, add

exponents• When dividing, subtract

exponents. (divisor from dividend)

Multiplication and Division using Scientific Notation

• Example

Dimensional Analysis

Dimensional Analysis – is a systematic approach to problem solving that uses conversion factors to move, or convert, from one unit to another.• Example

Conversion Factor

Conversion Factor - Is a ratio of equivalent values having different units.• Examples:

• 1000m / 1km• 1 hr / 3600s• 1 ml / 1 cm3

Practice Problems• CALM: Unit 1:2

End 1:2

1:3 Uncertainty in Data

Goals and Objectives:• 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.

Uncertainty in Data

Accuracy – is how close a measure value is to an accepted value.

Precision - Is how close a series of measurements are to one another. • The amount of uncertainty in a

measurement• More precise = less uncertainty

Precision in Measurements• When measuring any item,

write all digits that are confirmed and one estimated digit.

• Example

Error

Error is the difference between an experimental value and an accepted value.

• Error = experimental value – accepted value

• Example

Percent Error

Percent error expresses error as a percentage of the accepted value • Percent error =

Significant FiguresRules for Significant Digits

1. Nonzero digits are always significant.2. Zeroes are sometimes significant, and sometimes they

are not.a. Zeroes at the beginning of a number (used just to

position the decimal point) are never significant.b. Zeroes between nonzero digits are always

significant.c. Zeroes at the end of a number that contains a

decimal point are always significant.d. Zeroes at the end of a number that does not contain

a decimal point may or may not be significant.i. Scientific notation is used to clarify these

numbers.

Significant FiguresRules for Significant Digits

3. Exact numbers can be considered as having an unlimited number of significant figures.

4. In addition and subtraction, the number of significant digits in the answer is determined by the least precise number in the calculation.a. The number of significant figures to the right of

the decimal in the answer cannot exceed any of those in the calculation.

5. In multiplication and division, the answer cannot have more significant digits than any number in the calculation.

Significant Figures• Examples

Rounding Numbers• When rounding numbers to the

proper number of significant digits, look to the right of the last significant digit. • 1-4: round down the last sig

fig• 5-9: round up the last sig fig.

Rounding Numbers• Examples:• 54.3654 to 4 sig figs:

• To 3 sig figs:• To 2 sig figs:• To 1 sig fig:

Practice Problems• CALM: 1:3

1:4 Representing Data

Goals and Objectives• Create graphs to reveal patterns in

data.• Interpret graphs.• Explain how chemists describe

submicroscopic matter.

Representation of Data

Graph is a visual display of data• Circle graphs (pie chart) – display

parts of a whole.• Bar graphs – shows how a

quantity varies across categories• Line graphs – most graphs used in

chemistry

Rules for Good GraphingRules for Good Graphing on Paper:

1. All graphs should be on graph paper. 2. Identify the independent and dependent variables in

your data.a. The independent variable is plotted on the

horizontal axis (x-axis) and the dependent variable is plotted on the vertical axis (y-axis).

3. Determine the range of the independent variable to be plotted.

4. Spread the data out as much as possible. Let each division on the graph paper stand for a convenient unit. This usually means units that are multiples of 2, 5 or 10…etc.

Rules for Good Graphing

Rules for Good Graphing on Paper:

5. Number and label the horizontal axis. The label should include units.

6. Repeat steps 2. through 4. for the dependent variable.7. Plot the data points on the graph.8. Draw the best-fit straight or smooth curve line that

passes through as many points as possible. Do not use a series of straight-line segments to connect the dots.

9. Give the graph a title that clearly tells what the graph represents (y vs. x values).

Rules for Good GraphingRules for Good Graphing on the Computer:

1. From the insert menu on the Microsoft word program choose insert chart.

2. Identify the independent and dependent variables in your data.a. The independent variable is plotted on the horizontal

axis (x-axis) and the dependent variable is plotted on the vertical axis (y-axis).

3. Insert data in the excel window that opens. Be sure to pay attention to the excel column vs. graph axes location.

4. Through the toolbox menu, give the graph a title that clearly tells what the graph represents. (y vs. x variable).

5. Through the toolbox menu, give the axes in the graph labels that include units.

Representing Data

Linear relationship – variables are proportionally related• Line of best-fit is a straight line but is

not perfectly horizontal or vertical.

Representing Data

Slope – is equal to the change in y divided by the change in x• Rise/run• Δy/Δx

Representing Data

Interpolation – the reading of a value from any point that falls between recorded data points• When points on a line graph are

connected, the data is considered to be continuous.

Representing Data

Extrapolation – the process of estimating values beyond the plotted points.• The line of best fit is extended

beyond the scope of the data

Representing Data

Model – is a visual, verbal or mathematical explanation of experimental data. • Example

Practice Problems• No homework

• End 1:4

1:5 Scientific Method and ResearchGoals and Objectives• Identify the common steps of scientific

methods.• Compare and contrast types of data.• Identify types of variables.• Describe the difference between a

theory and a scientific law.• Compare and contrast pure research,

applied research, and technology

Scientific Method and Research

Scientific Method – is a systematic approach and organized process used in scientific study to do research• Observation• Hypothesis• Experiments• Conclusion

Scientific Method• Observation – is an act of gathering

information.• Qualitative – information that

describes color, odor, shape or other physical characteristic

• Quantitative – information taken in the form of a measurement.• Temperature, pressure, volume,

quantity, mass

Scientific Method• Hypothesis – is a tentative

explanation for what has been observed.

Scientific Method• Experiments – is a set of controlled

observations that test the hypothesis.• Independent variable – the variable

that is controlled or changed incrementally.

• Dependent variable – the value that changes in response to the independent variable.

• Control – is a standard for comparison.

Scientific Method

• Conclusion – is a judgment based on the information obtained.

Scientific Method

Scientific Theory and Law

Theory – is an explanation of a natural phenomenon based on many observations and investigations over time.

Scientific Law- a relationship in nature that is supported by many experiments.

Scientific Research• Pure research – is done to gain

knowledge for the sake of knowledge itself.

• Applied research – is research undertaken to solve a specific problem

Practice Problems• CALM: 1:5

What is data?

What can data tell us?

THE END