General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake Welcome to Chemistry 121 © 2013 Pearson Education, Inc.

Chapter 1 Chemistry and Measurements General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake Chapter 1 Chemistry and Measurements Lectures © 2013 Pearson Education, Inc.

What is Chemistry? Chemistry is the study of matter and its composition, structure, properties, and reactions Chemsitry occurs all around you, for example, when you cook food, add chlorine to your pool, digest food, and drop an antacid tablet in a glass of water.

Success in Chemistry 121 Regular attendance, active participation in problem solving Ask questions early and often! Seek extra help as needed – show up before class, take advantage to tutoring sessions Follow the suggestions given in chapter one of the text book, learn how to use the different features of your text book

Using your textbook Before reading, review topics in Looking Ahead. Review Learning Goals at the beginning of each section. Solve Concept Checks to help you understand the key ideas in each chapter. After reading, work through Sample Problems and try the associated Study Checks. Work the sets of Questions and Problems at the end of each section.

Active Learning Use Active Learning methods to help you learn chemistry. Read all assigned materials before you attend lectures. Note questions you have about the reading to discuss with your instructor Practice problem solving. Attend the office hours for help.

Form a Study Plan

Chemistry and Measurements General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake Chapter 1 Chemistry and Measurements © 2013 Pearson Education, Inc.

Sec. 1.3 Measurement in Science We use measurements in everyday life, such as walking 2.1 km to campus, carrying a backpack with a mass of 12 kg, and observing when the outside temperature has reached 22 oC. Notice that all measurements have 2 components A numerical value A unit written after the numerical value, to indicate the type of measurement made.

Units of Measurement: The Metric and SI Systems The metric system and SI (Système International) are used for length, volume, mass, temperature, and time, in most of the world, and everywhere by scientists.

Units in the Metric System In the metric and SI systems, one unit is used for each type of measurement. Measurement Metric Base Unit SI Unit Length meter (m) meter (m) Volume liter (L) cubic meter (m3) Mass gram (g) kilogram (kg) Temperature Celsius (C) Kelvin (K) Time second (s) second (s)

Length Measurement Length uses the unit meter (m) in both the metric and SI systems. uses centimeters (cm) for smaller units of length. The letter “c” in front of the “m” is called a metric prefix and denotes a specific power of 10

Converting Between Different Units of Length -- Inches, Centimeters, and Meters Useful relationships between units of length

Volume Measurement Volume is the space occupied by a substance. uses the unit liter (L) in the metric system. uses the unit cubic meter (m3) in the SI system. is measured using a graduated cylinder in units of milliliters (mL).

Converting between Quarts, Liters, and Milliliters Useful relationships between units of volume

Mass Measurement The mass of an object is a measure of the quantity of material it contains. measured in grams (g) for small masses. is measured in kilograms (kg) in the SI system. The standard kilogram for the United States is stored at the National Institute of Standards and Technology.

Converting Between Pounds, Grams, and Kilograms Useful relationships between units of mass

Temperature Measurement measured on the Celsius (C) scale in the metric system, measured on the Kelvin (K) scale in the SI system, and 18°C or 64°F on this thermometer. Temperature indicates how hot or cold a substance is, and is

Section 1.4 Scientific Notation is used to write very large or very small numbers. is used to give the width of a human hair (0.000 008 m) as 8 x 10-6 m. for a large number such as 100 000 hairs is written as 1 x 105 hairs.

Writing Numbers in Scientific Notation A number in scientific notation contains a coefficient between 1 and 10 and a power of 10 and a unit. When converting a number from standard notation to scientific notation, the decimal point is moved until there is only be one digit to the left of the decimal point For numbers larger than 1, the power of 10 is positive. For numbers less than 1, the power of 10 is negative 0.0075 L = 7.5 x 0.001 = 7.5 x 10-3 L

Some Powers of Ten

Scientific Notation and Calculators You can enter a number in scientific notation on many calculators using the EE or EXP key. Use the (+/−) key to change the value of the exponent from positive to negative.

Scientific Notation and Calculators You can enter a number in scientific notation on many calculators using the EE or EXP key. Use the (+/−) key to change the value of the exponent from positive to negative.

Scientific Notation and Calculators When a calculator display appears in scientific notation, it is shown as a number between 1 and 10 followed by a space and the power of 10.

Scientific Notation and Calculators To write this number in correct scientific notation, write the coefficient and use the power of 10 as an exponent.

Converting Scientific Notation to a Standard Number When a number in scientific notation has a positive power of 10, move the decimal point to the right for the same number of places as the power of 10 and add placeholder zeros to give the additional decimal places needed.

Converting Scientific Notation to a Standard Number When a number in scientific notation has a negative power of 10, move the decimal point to the left for the same number of places as the power of 10 and add placeholder zeros in front of the coefficient as needed.

1.5 Measured Numbers and Significant Figures General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake Chapter 1 Chemistry and Measurements 1.5 Measured Numbers and Significant Figures Lectures © 2013 Pearson Education, Inc.

Representing Measured Numbers Section 1.5 Measured Numbers and Significant Figures Representing Measured Numbers Measured numbers are numbers obtained by using measuring devices, such as a scale or analytical balance, a graduated cylinder, a clock or stopwatch, or a ruler

Writing down measured numbers Make sure you write down all numbers in the measurement and include the measurement unit The number of digits you record will depend on the sentsitivity of the measuring device being used For example, on a metric ruler with lines marking divisions of 0.1cm, write the length to 0.1 cm and estimate the value of the final number to 0.01 cm by visual inspection (you can estimate one decimal place beyond the smallest increments on the measuring device The length of the wood shown to the left would be written down as 4.55 cm

The Concept of Significant Figures When making a measurement, the number of digits written down include all the digits you are certain of plus the first estimated digit. A number is a significant figure if it is a nonzero number. (234 g, 3 SF) a zero between nonzero numbers. (50071 g, 5 SF) a zero at the end of a decimal number. (50.00 m, 4 SF) the coefficient of a number is written in scientific notation. (2.0 x 103 m, 2 SF)

The Atlantic-Pacific Rule For Significant Digits Imagine your number in the middle of the country Pacific Atlantic If a decimal point is present, start counting digits from the Pacific (left) side of the number, The first sig fig is the first nonzero digit, then any digit after that. e.g. 0.003100 would have 4 sig figs

The Atlantic-Pacific Rule For Significant Digits Imagine your number in the middle of the country Pacific Atlantic If the decimal point is absent, start counting digits from the Atlantic (right) side, starting with the first non-zero digit. The first sig fig is the first nonzero digit, then any digit after that e.g. 31,400 ( 3 sig. figs.)

Scientific Notation and Significant Zeros When one or more zeros in a large number are significant, they are shown more clearly by writing the number in scientific notation. 5,000. kg 5.000 x 103 kg If zeros are not significant, we use only the nonzero numbers in the coefficient. 5,000 kg 5 x 103 kg

Exact Numbers Exact numbers are those numbers obtained by counting items. those numbers in a definition comparing two units in the same measuring system. not measured and do not affect the number of significant figures in a calculated answer.

1.6 Significant Figures in Calculations General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake Chapter 1 Chemistry and Measurements 1.6 Significant Figures in Calculations Lectures © 2013 Pearson Education, Inc.

Sec. 1.6 Mathematical Calculations and Significant Figures The number of significant figures in measured numbers are used to limit the number of significant figures in the final answer. Calculators do not provide the appropriate number of significant figures.

Rounding Off To represent the appropriate number of significant figures, we use "rules for rounding." 1. If the first digit to be dropped is 4 or less, then it, and all following digits are simply dropped from the number. 2. If the first digit to be dropped is 5 or greater, then the last retained digit of the number is increased by 1.

Rounding Off

Multiplication and Division When multiplying or dividing use the same number of significant figures (SF) as the measurement with the fewest significant figures, and the rounding rules to obtain the correct number of significant figures.

Multiplication and Division When multiplying or dividing use the same number of significant figures (SF) as the measurement with the fewest significant figures, and the rounding rules to obtain the correct number of significant figures.

Adding Significant Zeros Sometimes we add one or more significant zeros to the calculator display in order to obtain the correct number of significant figures needed. Example: Suppose the calculator display is 4, and you need 3 significant figures. 4 becomes 4.00 1 SF 3 SF

Addition and Subtraction When adding or subtracting, use the same number of decimal places as the measurement with the fewest decimal places and the rounding rules to adjust the number of digits in the answer. one decimal place two decimal places calculated answer final answer (with one decimal place)

Sec. 1.7 Metric Prefixes and Equalities A prefix in front of a unit increases or decreases the size of that unit. makes units larger or smaller than the initial unit by one or more factors of 10. indicates a numerical value.

Metric and SI Prefixes Prefixes that increase the size of the unit:

Metric and SI Prefixes Prefixes that decrease the size of the unit:

Daily Values for Selected Nutrients

Metric Equalities An equality states the same measurement in two different units. can be written using the relationships between two metric units. Example: 1 meter is the same as 100 cm and 1000 mm.

Measuring Length The metric length of 1 meter is the same length as 10 dm, 100 cm, and 1000 mm. Q How many millimeters (mm) are in 1 centimeter (cm)?

Measuring Volume

Measuring Mass Several equalities can be written for mass in the metric (SI) system.

Sec. 1.8 Solving Problems In Chemsitry Using Dimensional Analysis and Conversion Factors Dimensional Analysis is a problem-solving method used in science It depends on your ability to identify the numerical information given by the problem, and your ability to identify the numerical information you are supposed to find when solving the problem. The link between the known value (given) and the unkown value (find) is called a Converion Factor

Equalities Equalities use two different units to describe the same measured amount. are written for relationships between units of the metric system; between U.S. units or between metric and U.S. units. Examples:

Equalities and Conversion Factors Equalities are written as a fraction. used as conversion factors. can be represented with one equality in the numerator and the second equality in the denominator. Examples:

Common Equalities

Exact and Measured Numbers in Equalities Equalities between units of the same system are definitions with numbers that are exact. different systems (metric and U.S.) are measurements with numbers that have significant figures. The equality of 2.54 cm = 1 in. is an exception and considered to be exact.

Metric Conversion Factors We can write equalities as conversion factors.

Metric-US Conversion Factors Metric–US conversion factors are written as a ratio with a numerator and denominator. Example:

Equalities on Food Labels The contents of packaged foods in the U.S. are listed in both metric and U.S. units. indicate the same amount of a substance in two different units.

Percent as a Conversion Factor A percent factor uses a ratio of the parts to the whole in a fraction. uses the same units for the parts and whole. uses the value 100 for the whole. can be written as two factors. Example: A food contains 18% (by mass) fat.

Chapter 1 Chemistry and Measurements General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake Chapter 1 Chemistry and Measurements 1.9 Problem Solving Lectures © 2013 Pearson Education, Inc.

Guide to Problem Solving Using Conversion Factors There are 4 steps to solving problems with conversion factors.

Steps to Solving the Problem If a person weighs 164 lb, what is the body mass in kilograms? Step 1 State the given and needed quantities. Analyze the Problem Step 2 Write a plan to convert the given unit to the needed unit. lb US–Metric kilograms Factor Given Need 164 lb kilograms

Steps to Solving the Problem If a person weighs 164 lb, what is the body mass in kilograms? Step 3 State the equalities and conversion factors. Step 4 Set up the problem to cancel units and calculate the answer.

Steps to Solving the Problem If a person weighs 164 lb, what is the body mass in kilograms? Step 3 State the equalities and conversion factors. Step 4 Set up the problem to cancel units and calculate the answer.

Using Two or More Factors Often, two or more conversion factors are required to obtain the unit needed for the answer. Unit 1 Unit 2 Unit 3 Additional conversion factors are placed in the setup to cancel each preceding unit.

Example: Problem Solving How many minutes are in 1.6 days? Step 1 State the given and needed quantities. Analyze the Problem. Step 2 Write a plan to convert the given unit to the needed unit. days time time min factor 1 factor 2 Given Need 1.6 days minutes

Example: Problem Solving How many minutes are in 1.6 days? Step 3 State the equalities and conversion factors. Step 4 Set up problem to cancel units and calculate answer.

Density Density compares the mass of an object to its volume. is the mass of a substance divided by its volume. are measured in g/L for gases. are measured in g/cm3 or g/mL for solids and liquids. Density expression:

Chapter 1 Chemistry and Measurements General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake Chapter 1 Chemistry and Measurements 1.10 Density Lectures © 2013 Pearson Education, Inc.

Density Density compares the mass of an object to its volume. is the mass of a substance divided by its volume. are measured in g/L for gases. are measured in g/cm3 or g/mL for solids and liquids. Density expression:

Densities of Common Substances

Density Calculations

Calculating Density If a 0.258-g sample of HDL has a volume of 0.215 cm3, what is the density, in g/cm3, of the HDL sample? Step 1 State the given and needed quantities. Analyze the Problem. Step 2 Write the density expression. Given Need 0.258 g HDL 0.215 cm3 HDL density in g/cm3 of HDL

Calculating Density If a 0.258-g sample of HDL has a volume of 0.215 cm3, what is the density, in g/cm3, of the HDL sample? Step 3 Express mass in grams and volume in milliliters (mL) or cm3. Step 4 Substitute mass and volume into the density expression and calculate the density.

Sink or Float Ice floats in water because the density of ice is less than the density of water. Aluminum sinks in water because its density is greater than the density of water.

Problem Solving using Density Density can be written as a conversion factor.

Problem Solving using Density Density can be used as a conversion factor. A density of 3.8 g/mL, can be written as an equality, or written as conversion factors.

Problem: Density as a Conversion Factor If the density of milk is 1.04 g/mL, how many grams of milk are in 0.50 qt of milk? Step 1 State the given and needed quantities. Analyze the Problem.

Problem: Density as a Conversion Factor If the density of milk is 1.04 g/mL, how many grams of milk are in 0.50 qt of milk? Step 1 State the given and needed quantities. Analyze the Problem.

Problem: Density as a Conversion Factor If the density of milk is 1.04 g/mL, how many grams of milk are in 0.50 qt of milk? Step 2 Write a plan to calculate needed quantity. volume US–Metric density mass factor factor Step 3 Write equalities and conversion factors.

Problem: Density as a Conversion Factor If the density of milk is 1.04 g/mL, how many grams of milk are in 0.50 qt of milk? Step 4 Set up the problem to calculate the needed quantity.

Specific Gravity Specific Gravity (sp gr) is the relationship between the density of a substance and the density of water. is determined by dividing the density of the sample by the density of water. is a unitless quantity.

Specific Gravity Specific Gravity is measured by an instrument called a hydrometer.