Chapter 1



Chapter 1

Chemistry: The Study of Change

Study Objectives

Sections 1.2-1.3

1. Describe matter and its physical states.

2. Define chemistry

Sections 1.4-1.6

3. Distinguish between elements, compounds, and solutions.

4. Distinguish between homogenous and heterogeneous mixtures.

5. Distinguish between physical and chemical properties of a substance.

Section 1.7

6. Express base units and derived units of the SI.

7. Learn the prefixes used in the SI.

Section 1.8

8. Express numbers and perform calculations in exponential notation.

9. Determine the number of significant figures in a given number and in a number that is the result of a mathematical calculation.

10. Round off numbers to the desired digit.

Section 1.9

11. Construct conversion factors from known equalities.

12. Solve problems using the factor-label method.

13. Solve problems involving density.

About Chemistry

• __________ is the study of ______ and the _______ it undergoes.

• ______ is defined as anything that has ____ and occupies _____.

▪ The three physical states of matter are _____, ______, and ___.

▪ All matter exists in one or another of these three states, depending on the ___________ and ________ of the surrounding environment.

• Chemists are concerned with developing the tools used to study matter and the given forms of matter into new and different substances, and to the discovery of the properties and uses of these new materials.

▪ Chemists usually observe matter and the changes it undergoes in the ___________ world. This refers to the objects we can ___ and _____, and deal with everyday.

▪ However, our interpretations of matter involve atoms and molecules and their properties. Because atoms and molecules are so extremely _____, we refer to them as belonging to the ___________ world.

Matter and Its Properties

• A ____ _________ is a form of matter that has ________ ___________ and ________ properties.

▪ Examples are water, table salt, and iron.

▪ Just as each individual person has a set of characteristics, such as fingerprints and color of eyes and hair, each pure substance has characteristic properties.

• There are two types of pure substance: ________ and _________.

▪ An _______ is a ____ _________ that cannot be __________ into simpler substances by ________ ________ _________.

← ________ are the building blocks of which all compounds are composed.

← Nitrogen, oxygen, and iron are examples of elements.

▪ _________ are pure substances that are composed of ___ or ____ ________ combined in ________ ___________.

← Compounds can be ______ ____ into the elements of which they are composed by ________ _____.

← Water and table salt are compounds.

• The action of an electric current, called ____________, is one method that can be used to _________ both water and molten table salt into their constituent ________.

▪ Pure water consists of 89 % oxygen and 11 % hydrogen by mass.

▪ Pure salt contains 39% sodium and 61% chlorine.

• Pure substances can be brought together to form ________.

▪ ________ are combinations of two more substances with ________ ___________.

▪ They can be ___________ or _____________ depending on the state of subdivision of the components.

• Salt water is a _______ _______ of table salt (NaCl) and water.

▪ The original crystals of salt have dissolved and are dispersed ______.

▪ On the ordinary scale of observation we cannot detect any chemical or physical differences between adjacent regions of the _______.

← The particles of salt are too small to observe.

▪ A mixture that has the ____ composition throughout is said to be a ___________ mixture.

▪ The properties of a homogeneous mixture vary since they depend on the _______ ___________.

← For example, the ________ of steel, a solid mixture of ____ and ______, depends on the __________ of ______ that is added to ____.

▪ Homogeneous mixtures are also called _________.

• _____________ mixtures are ___ _______ in composition.

▪ And indeed the individual particles of their components can often be ____ by the _______ ___.

▪ For example, when preparing home-made ice cream, you use a mixture of ice and rock salt.

← This is a heterogeneous mixture.

← The individual chunks (particles) of ice and salt are clearly visible, and the particles are so large, they are not evenly dispersed.

▪ The composition of this mixture ______ from place to place within the mixture itself.

▪ _______ ___ is actually a heterogeneous mixture.

← It consists of nitrogen, oxygen, and argon gases, but also contains solid particles of pollen and dust.

• Any mixture, whether it be homogeneous or heterogeneous, can be separated into its pure components by ________ _____.

Physical and Chemical Properties of Matter

• ________ __________ are those properties that can be measured and observed _______ ________ the ________ or composition of the substance.

▪ Physical properties include color, hardness, solubility, density, specific heat, melting point, and boiling point.

• ________ _______ are those that take place with __ ______ in ________ ___________.

▪ _______ of a substance from one _____ of matter to another do not change its chemical composition and are examples of ________ _______.

▪ The three forms of water we call ice, liquid water, and steam are all the same substance, just different physical states.

• ________ __________ most often are descriptions of reactions that a substance undergoes when brought in contact with other substances.

▪ In a chemical reaction the original substance or substances are changed into ___ __________.

▪ When sodium metal and chlorine gas are heated together, a white solid called sodium chloride is formed.

← That this is a chemical change is evident by the observation that sodium, a shiny metal, and chlorine, a pale yellow green gas, have disappeared, and in their place is a substance with a completely new set of properties.

← Sodium chloride is a white solid that melts at very high temperatures.

• All properties of matter are either _________ or _________ properties.

▪ _________ properties depend on the ______ __ ______ being considered.

← ______ and ____ are examples.

▪ In contrast, ___________ and _______ are two properties that __ ___ ______ __ ___ ______ __ ____ present.

▪ Thus, they are _________ properties.

Units of Measurement

• Since 1960 a coherent system of units, known as the __, has been in effect and is accepted among scientists and engineers.

• SI is the abbreviation for Le Systeme International d’Unites.

• The SI has as its base units: the _________ (__) for mass, the _____ (__) for length, the ______ (__) for time, the ______ (__) for temperature, and the ____ (___) for amount of substance.

• ____________ of base units produce _______ _____. For example, velocity is distance traveled per unit of time.

▪ Therefore, velocity has units of meters per second (m/s) and is a derived unit rather than a base unit.

• A major advantage of the SI is that it uses the decimal system.

▪ A list of the SI ________ is given in Table 1.3.

▪ These ________ will be used throughout your study of chemistry.

▪ Note that in the SI the same prefix can be applied to any base unit or derived unit.

▪ Thus the prefix milli can be used to describe a unit that is 1/1000 of a gram, or 1/1000 of a meter, or 1/1000 of any SI unit.

1 milligram = 1/1000 gram

1 millimeter = 1/1000 meter

1 millisecond = 1/1000 second

• ______ is a derived unit. It can be expressed in terms of ______ _____ because for rectangular solids volume is equal to length times width times height all of which have the base unit meters.

volume = length x width x height = length3

volume = m x m x m = m3

• The SI unit for volume is the _____ _____ (__) which is the volume of a cube 1 m on each edge.

▪ This unit is too large and related units such as the _____ __________ (___) and cubic decimeter (dm3) are often used.

• The volume of a _____ is usually measured in ______ (__).

▪ A liter is roughly the size of a quart (1.06 qt). A liter is the volume of a cube with an edge of 10 cm, and therefore is 1000 cm3.

▪ The volume unit you are most likely to use in chemistry is the milliliter (mL). One mL is 0.001 L, and so 1000 mL equal 1 L.

▪ Since 1 L = 1000 cm3 = 1000 mL, then one milliliter (mL) is _____ to one cubic centimeter (cm3).

1 mL = 1 cm3

• ________ is an important physical property of objects and substances.

• The _______ of an object is defined as the ratio of its ____ to its ______.

▪ Density has units that are _______ from the base units for mass and volume which are kilograms per cubic meter.

▪ However, it is more convenient to report densities in units of _____ ___ _____ __________ or _____ ___ __________.

• Chemists use two temperature scales, the ______ scale (K) and the _______ scale (°C).

• A third scale, the Fahrenheit scale (°F), is commonly used in the United States.

• The _______ scale defines ___ as the ________ _____ of _____ and _____ as the _______ _____ of _____.

Handling Numbers

• Many of the quantities (numbers) encountered in chemistry are more easily manipulated when they are written in a form known as __________ or ___________ ________.

• Very large or very small numbers are expressed as N x 10n, where N is a number between 1 and 10 and n corresponds to the exponents 1, 2, 3, etc.

• Recall that the exponent tells you how many times to multiply the number 10 by itself. Therefore:

|103 = 10 x 10 x 10 |= 1000 |

|102 = 10 x 10 |= 100 |

|101 = 10 |= 10 |

|100 |= 1 |

• To write the number 5000 in exponential notation, we could rewrite it as 5 x 1000. But 1000 can be written 10 x 10 x 10, or just 103. Therefore, 5000 can be written as 5 x 103.

▪ More simply, to find the exponent of 10, just _____ the ______ of ______ that the decimal point must be moved to the ____ to give the number N.

▪ For the number 5000, moving the decimal point three places to the left gives 5 x 103.

• __________ _______ can also be expressed in scientific notation, but in this case the decimal point will be moved to the right and the exponent will be a ________ ______ (–n).

▪ For the number 0.05, the decimal point must be moved two places to the right to give N (a number between 1 and 10).

▪ In exponential notation 0.05 becomes 5 x 10–2.

• Multiplication and division of numbers that are expressed in exponential notation are accomplished by operating on the coefficients (N) and exponentials (n) __________.

• Recall when ___________ two exponential numbers that the exponents are _____.

• When ________ exponential numbers, we ________ the exponent in the denominator from the exponent in the numerator.

Significant Figures

• Measurements, and calculations based on measurements, must be reported so as to convey information about the number of __________ digits.

• The ___________ _______ are those digits in a measured number that include all _______ ______ plus ___ having ___________.

▪ If we measure the length of a desktop with a meterstick calibrated in millimeters and find the length to be 972.5 mm, then the digits 9, 7, and 2 mean there are 9 hundreds, 7 tens, and 2 ones, and because of the calibrations, these digits are _______.

▪ Five-tenths, however, is an estimate because it falls between the finest calibrations.

▪ Someone else might read it as 0.6 or 0.4.

▪ The result could be expressed with error limits as 972.5 ± 0.1 mm.

▪ This measurement provides three certain digits and one uncertain digit.

▪ All of these provide useful information, and we say the number 972.5 has four significant figures.

• Always take care that the numbers you write reflect the proper number of meaningful digits.

• The process of determining the correct number of significant figures after a calculation depends on the type of calculation.

Guidelines for Writing Significant Figures

• To determine the number of significant digits that are present in a written number, use the following rules:

▪ Count ___ numbers significant ______:

← _______ _____ 0.0002

← ________ _____ with a decimal point 2500

• In most cases the numbers we measure are used to calculate other __________.

• Care must be exercised to report the ______ ______ of significant figures in the calculated result.

• This is extremely important when electronic calculators are used because they give answers with eight and ten digits.

• The rule used is that the ________ of the result is _______ by the _____ ________ measurement.

▪ In multiplication and division, the number of significant figures in a calculated result is determined by the ________ ___________ that has the ______ number of significant digits.

▪ Thus, if a number with three significant figures is multiplied by a number with four significant figures, the computed result will have only three significant figures.

▪ Even if a calculator computes eight digits, most of them will be ___________ in terms of their physical significance.

▪ A number is _______ off to the desired number of significant figures by dropping one or more digits to the right.

• In addition and subtraction, the number of significant figures in the answer depends on the original number in the calculation that has the ______ ______ to the _____ of the _______ _____.

▪ For example, when ______:

102.226

2.51

846.     [pic]fewest digits to the right of the decimal point

950.736

7, 3 and 6 are nonsignificant digits

951 [pic]rounded off

▪ and when ___________:

102.25

–99.3 [pic]fewest digits to the right of the decimal point

2.95

5 is a nonsignificant digit

3.0 [pic]rounded off

• It is important to remember when adding or subtracting, that the number of significant figures in the answer is not necessarily determined by the ________ having the fewest significant figures, which is true for multiplication and division.

Accuracy and Precision

• ________ tells us how _____ a measurement is to the ____ _____ of the quantity that was measured.

• _________ refers to how _______ two or more measurements of the same quantity _____ with one another.

The Factor-Label Method of Solving Problems

• The ______-_____ ______ (also called ___________ ________) is a simple but powerful technique that can be applied to a great variety of calculation problems.

▪ In this method the _____ (labels) of the quantities involved are used as a guide in setting up a calculation.

▪ The method is based on the use of conversion factors and on the idea that units or dimensions of various quantities can be handled algebraically in the same way as numbers are handled.

• Conversion factors are constructed from equalities such as the following:

2.540 cm = 1 in 1000 g = 1 kg 24 h = 1 day

• These conversion factors are examples of unit factors.

▪ Each unit factor is equal to __ (unity) because the _________ equals the ___________.

▪ Treating units in the same fashion as numbers are treated in algebra is the essential element of the factor-label method.

▪ For example, multiplying inch by inch yields inches squared, or square inches.

in x in = in2

▪ One hour divided by one hour is equal to 1, and we say that the units cancel:

|h |= 1 |

|h | |

• In the factor-label method we multiply a given quantity by appropriate conversion factors in order to arrive at a desired quantity.

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