introductory chemistry: chemistry and you chapter 1

Introductory Chemistry:Introductory Chemistry:

Chemistry Chemistry and Youand You

Chapter 1

Tuesday, 9/9/14

• Learning Target: Students must be able to explain why chemistry is central to many human endeavors.

Chapter 1 2

Chapter 1 3

Learning Chemistry• Different people learn

chemistry differently.

• What do you see in the picture?

• Some people see a vase on a dark background, some people see two faces.

Chapter 1 4

Problem Solving• Connect the 9 dots using only four straight lines.

• Experiment until you find a solution.

• However, we have used 5 straight lines.

• No matter which dot we start with, we still need 5 lines.

Chapter 1 5

Problem Solving• Are we confining the

problem?

• We need to go beyond the 9 dots to answer the problem.

Lab Safety SymbolsIdentify the following symbols

A. B. C.

D. E. F.

G. H. I.

• What is the definition of chemistry?

– The science that studies the composition of matter and its properties.

Chapter 1 8

Chemistry: The Central Science

• Why????

• Most other sciences demand an understanding of basic chemical principles, and Chemistry is often referred to as the Central Science

Chapter 1 9

Modern Chemistry• Chemistry is a science that studies the composition of

matter and its properties.

• Chemistry is divided into several branches:

– Organic chemistry is the study of substances containing carbon

– Inorganic chemistry is the study of all other substances

– Biochemistry is the study of substances derived from plants and animals

– Analytical is the study of matter and ways to study the properties of matter.

– Physical is the physics of chemistry. Thermodynamics and quantum mechanics.

Wednesday, 9/10/14

Learning Target:

Students must know the metric system, SI units and derived units.

Learning Outcome:

Measurement Pre-Lab

Chapter 1 10

The Standard Units• Scientists have agreed on a set of

international standard units for comparing all our measurements called the SI units

Quantity Unit Symbol

length meter m

mass kilogram kg

time second s

temperature kelvin K

Length• SI unit = meter

– About a yard• Commonly use centimeters (cm)

– 1 m = 100 cm– 1 cm = 0.01 m = 10 mm– 1 inch = 2.54 cm

Mass• Measure of the amount of matter

present in an object– weight measures the gravitational pull

on an object, which depends on its mass

• SI unit = kilogram (kg)– about 2 lbs. 3 oz.

• Commonly measure mass in grams (g) or milligrams (mg)

Time

• measure of the duration of an event

• SI units = second (s)

Temperature Scales

• Fahrenheit Scale, °F– used in the U.S.

• Celsius Scale, °C– used in all other countries

• Kelvin Scale, K– The SI unit for

temperature

Prefix Multipliers in the SI System

Prefix SymbolDecimal

EquivalentPower of 10

mega- M 1,000,000 Base x 106

kilo- k 1,000 Base x 103

deci- d 0.1 Base x 10-1

centi- c 0.01 Base x 10-2

milli- m 0.001 Base x 10-3

micro- 0.000 001 Base x 10-6

nano- n 0.000 000 001 Base x 10-9

pico p 0.000 000 000 001 Base x 10-12

What Is a Measurement?

• quantitative observation

• every measurement has a number and a unit

• every digit written is certain, the last one which is estimated

Estimation in Weighing

• What is the uncertainty in this reading?

Thursday, 9/11/14

Learning Target:

Students must be able to compare and contrast accuracy and precision in measurement.

Learning Outcome:

Complete “Measurement Lab”

Chapter 1 20

Uncertainty in Measured Numbers

uncertainty comes from:• limitations of the instruments used for

comparison, • the experimental design, • the experimenter, • nature’s random behavior

Precision and Accuracy• accuracy is an indication of how close a

measurement comes to the actual value of the quantity

Percent error =

• precision is an indication of how reproducible a measurement is

Accuracy vs. Precision

Precision• imprecision in measurements is caused

by random errors– errors that result from random fluctuations

• we determine the precision of a set of measurements by evaluating how far they are from the actual value and each other called standard deviation.

• Do multiple trials to lesson error and improve precision.

Accuracy• inaccuracy in measurement caused by

systematic errors– errors caused by limitations in the instruments

or techniques or experimental design

• we determine the accuracy of a measurement by evaluating how far it is from the actual value

• Use percent error to calculate how accurate you are

Mass & Volume• mass and volume are extensive

properties– the value depends on the quantity of

matter– extensive properties cannot be used to

identify what type of matter something is• if you are given a large glass containing 100 g

of a clear, colorless liquid and a small glass containing 25 g of a clear, colorless liquid - are both liquids the same stuff?

Mass vs. Volume of BrassMass grams

Volume cm3

20 2.4

32 3.8

40 4.8

50 6.0

100 11.9

150 17.9

Monday 9/15/14

Learning Target:

Know how to use significant figures in labs and in problems.

Learning Outcome:

Complete significant figures problems.

Chapter 1 28

Chapter 1 29

Accuracy versus Precision

Significant Figures

• the non-place-holding digits in a reported measurement are called significant figures

• significant figures tell us the range of values to expect for repeated measurements

• We use significant figures in science because measurement is always involved.

Counting Significant Figures

1) All non-zero digits are significant– 1.5 has 2 sig. figs.

2) Interior zeros are significant– 1.05 has 3 sig. figs.

3) Leading zeros are NOT significant –0.001050 has 4 sig. figs.

Counting Significant Figures

4) Trailing zeros may or may not be significant 1) If a decimal is present, trailing zeros are significant

• 1.050 has 4 sig. figs.

2) If a decimal is NOT present, trailing zeros are NOT significant.

• if 150 has 2 sig. figs. then 1.5 x 102

• but if 150. has 3 sig. figs. then 1.50 x 102

**These are considered ambiguous and should be avoided by using scientific notation

Determining the Number of Significant Figures in a Number

How many significant figures are in each of the following?

0.04450 m

5.0003 km

1.000 × 105 s

0.00002 mm

10,000 m

4 sig. figs.; the digits 4 and 5, and the trailing 0

5 sig. figs.; the digits 5 and 3, and the interior 0’s

4 sig. figs.; the digit 1, and the trailing 0’s

1 sig. figs.; the digit 2, not the leading 0’s

Ambiguous, generally assume 1 sig. fig.

Multiplication and Division with Significant Figures

• when multiplying or dividing measurements with significant figures, the answer must reflect the fewest number of significant figures

1) 5.02 × 89,665 × 0.10 =

2) 5.892 ÷ 6.10 =

Addition and Subtraction with Significant Figures

• when adding or subtracting measurements with significant figures, the answer should reflect the largest uncertainty

1) 5.74 + 0.823+ 2.651 =

2) 4.8 - 3.965 =

Roundingif the number after the place of the last significant

figure is:0 to 4, round down

– drop all digits after the last sig. fig. and leave the last sig. fig. alone

5 to 9, round up– drop all digits after the last sig. fig. and increase the last

sig. fig. by one

To avoid accumulating extra error from rounding, round only at the end, keeping track of the last sig. fig. for intermediate calculations

Roundingrounding to 2 significant figures

• 2.34 rounds to 2.3

• 2.37 rounds to 2.4

• 2.349865 rounds to 2.3

Roundingrounding to 2 significant figures

• 0.0234 rounds to 0.023

• 0.0237 rounds to 0.024

• 0.02349865 rounds to 0.023

Roundingrounding to 2 significant figures

• 234 rounds to 230

• 237 rounds to 240

• 234.9865 rounds to 230

Both Multiplication/Division and Addition/Subtraction with

Significant Figures

• First, evaluate the significant figures in the parentheses

• Second, do the remaining steps3.489 × (5.67 – 2.3) =

Perform the following calculations to the correct number of significant figures

4555.30015.45120.010.1 a)

5820.100

1.105

355.0

33.4526755.45299870.3562.4 c)

02.855.084.14 d)

b)

Example 1.6 Perform the following calculations to the correct number of

significant figures652.065219.04555.30015.45120.010.1 a)

4.9 8730.4

5820.100

1.105

355.0

80.5279904.5233.4526755.45299870.3562.4 c)

14.0142.002.855.084.14 d)

b)

Tuesday 9/16/14

Learning Target:

Know how to use and convert numbers into scientific notation.

Learning Outcome:

I will be able to use scientific notation in problems and convert standard notation into scientific notation.

Chapter 1 43

• Why are significant figures not important in your math class?

Chapter 1 44

Density• Ratio of mass:volume

– Solids = g/cm3

• 1 cm3 = 1 mL

– Liquids = g/mL– Gases = g/L

• Volume of a solid can be determined by water displacement – Archimedes Principle

Density

• Density : solids > liquids >>> gases– except ice is less dense than

liquid water!

• Heating an object generally causes it to expand, therefore the density changes with temperature

Density

• Iron has a density of 7.86 g/cm3. Could a block of metal with a mass of 18.2 g and a volume of 2.56 cm3be iron?

Density

• What volume would a 0.871 g sample of air occupy if the density of air is 1.29 g/L?

Wednesday, 9/17/14

Learning Target:

Be able to apply dimensional analysis to convert from one unit of measure to another.

Learning Outcome:

I will be able to complete single-step unit conversion problems.

Chapter 1 49

Units• Always include units in your calculations

– you can do the same kind of operations on units as you can with numbers

• cm × cm = cm2

• cm + cm = cm• cm ÷ cm = 1

Dimensional Analysis

• Using units as a guide to problem solving is called dimensional analysis

• This is the technique that we have learned to convert between two different units.

Problem Solving and Conversion Factors

• Conversion factors are relationships between two units– May be exact or measured

• Conversion factors are generated from unit equalities– e.g., 1 inch = 2.54 cm can give

or

in1

cm54.2cm54.2

in1

Problem Solving and Dimensional Analysis

• Arrange conversion factors so given unit cancels

– Arrange conversion factor so given unit is on the bottom of the conversion factor

• May string conversion factors

– So we do not need to know every relationship, as long as we can find something else the given and desired units are related to

unit desiredunitgiven

unit desiredunitgiven

• Using a ruler from the front counter, measure the length, width and height of a Chemistry textbook to the nearest 1 cm.

• How many meters wide is it?

• How many inches is the width of the textbook (2.54 cm = 1 in)? 

• How many feet is your textbook?

54

Thursday, 9/18/14

Learning Target:

Be able to apply dimensional analysis to convert from one unit of measure to another.

Learning Outcome:

I will be able to complete multi-step unit conversion problems.

Chapter 1 55

Warm-Up

Convert – 232.1 kPa to Pa

Chapter 1 56

Practice – Convert 154.4 lbs to kg

Practice – Convert 30.0 mL to quarts(1 L = 1.057 qt)

Volume• Derived unit (width x length x height)

– any length unit cubed• Measure of the amount of space

occupied• SI unit = cubic meter (m3)• Commonly measure solid volume in

cubic centimeters (cm3)– 1 m3 = 106 cm3

• Commonly measure liquid or gas volume in milliliters (mL)– 1 L is slightly larger than 1 quart– 1 mL = 1 cm3

How many cubic centimeters are there in 2.11 yd3?

Impossible Conversions

• Is it possible to find how many seconds in a kilogram?

• In order to do unit conversions they must be able to correspond to the same quantity.– For example, kilograms and pounds are both

units of mass.

Graphing in Science

• All graphing that is done in science must include the following:

1. A descriptive title

2. X and Y axis labeled with units.

3. The X – axis is the manipulated variable and the Y- axis is the responding variable.

4. A trend line (or line of best fit) to show the trend in the data that has been plotted.

Volume vs. Mass of Brass

0

20

40

60

80

100

120

140

160

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0

Volume, cm3

Mas

s, g

Convert 30.0 mL to quarts

Units & magnitude are correctCheck:• Check

0.03171 qt = 0.0317 qtRound:• Sig. figs. and

round

Solution:• Follow the concept plan to solve the problem

1 L = 1.057 qt1 L = 1000 mL

Concept Plan:

Relationships:

• Strategize

154.4 lbsLbs to kg

Given:Find:

• Sort information

65

Scientific Investigations

• Science is the methodical exploration of nature followed by a logical explanation of the observations.

• Scientific investigation entails:– planning an investigation– carefully recording observations– gathering data– analyzing the results

Chapter 1 66

The Scientific Method

• The scientific method is a systematic investigation of nature and requires proposing an explanation for the results of an experiment in the form of a general principle.

• The initial, tentative proposal of a scientific principle is called a hypothesis.

• After further investigation, the original hypothesis may be rejected, revised, or elevated to the status of a scientific principle.

Scientific Method

the careful noting and recording of natural phenomena

a test of a hypothesis or theory

a tentative explanation of a single or small number of natural phenomena

a general explanation of natural phenomena

a generally observed natural phenomenon

Chapter 1 68

Conclusions Continued• After sufficient evidence, a hypothesis becomes a

scientific theory.

• A natural law is a measurable relationship.

Chapter 1 69

Conclusions

• Scientists use the scientific method to investigate the world around them.

• Experiments lead to a hypothesis, which may lead to a scientific theory or a natural law.

• Chemistry is a central science with many branches.

• The impact of chemistry is felt in many aspects of our daily lives.

QUIZE - CHAPTER -1

1. What is the difference between a hypothesis and theory

2. According to the ancient Greeks, which of the following are not basic elements found in nature:

I. Air

II. Coal

III. Fire

IV. Earth

V. Gold

VI. WaterChapter 1 70