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Chapter 1 The Science of Chemistry

Section 1 What Is Chemistry? Section 2 Describing Matter

Section 3 How Is Matter Classified?



Working with the Properties and Changes of Matter• A chemical is any substance that has a definite

composition.

• A chemical reaction is the process by which one or more substances change to produce one or more new substances.

Section 1 What Is Chemistry?Chapter 1



Visual Concepts

Chemical

Chapter 1



Physical States of Matter

• The states of matter are the physical forms of matter which are solid, liquid, gas, and plasma.

• Macroscopic refers to what you can see with the unaided eye.

• Microscopic refers to what you would see if you could see individual atoms.




Physical States of Matter, continuedProperties of the Physical States

• Solids have a fixed volume and shape that result from the way their particles are arranged.

• Liquids have a fixed volume but not a fixed shape.

• Gases have neither fixed volume nor shape.




Water in Three States




Visual Concepts

Solid, Liquid and Gas

Chapter 1



Changes of Matter

• Physical changes are changes in which the identity of a substance doesn’t change.

• Changes of state are physical changes.

• Chemical changes occur when the identities of substances change and new substances form.




Changes of Matter, continuedChemical Changes

mercury(II) oxide mercury + oxygen

• Reactants are the substances are the left-hand side of the arrow.

• They are used up in the reaction.

• Products are the substances are the right-hand side of the arrow.

• They are made in the reaction.




Evidence of a Chemical Change




Changes of Matter, continuedEvidence of a Chemical Change

• Evidence that a chemical change may be happening generally falls into one of the following categories.

• the evolution of a gas

• the formation of a precipitate

• the release or absorption of energy

• a change in temperature or the giving off of light energy

• a color change in the reaction system




Visual Concepts

Chemical Reaction

Chapter 1



Matter Has Mass and Volume

• Matter is anything that has mass and volume.

• Volume is the space an object occupies.

• Mass is the quantity of matter in an object.

• Devices used for measuring mass in a laboratory are called balances.

• Weight is the force produced by gravity acting on a mass.

Section 2 Describing MatterChapter 1



Visual Concepts

Comparing Mass and Weight

Chapter 1



Units of Measurement

• When working with numbers, be careful to distinguish between a quantity and its unit.

• Quantity describes something that has magnitude, size, or amount.

• Unit is a quantity adopted as a standard of measurement.




Units of Measurement, continuedScientist Express Measurements in SI Units

• Scientists worldwide use a set of units called the Système Internationale d’Unités or SI.




Units of Measurement, continuedScientist Express Measurements in SI Units, continued

• Base units can be too large or too small for some measurements, so the base units may be modified by attaching prefixes.




Visual Concepts

SI (Système Internationale d’Unités )

Chapter 1



Visual Concepts

Conversion Factor

Chapter 1



Section 2 Describing Matter

Unit of Measurement, continuedConverting One Unit to Another

• A conversion factor is a simple ratio that relates two units that express a measurement of the same quantity.

• example: You can construct conversion factors between kilograms and grams as follows:

1 kg = 1000 g can be written as or

0.001 kg = 1 g can be written as

1 kg 1000 g 1000 g 1 kg

0.001 kg 1 g

1 g 0.or

001 kg

Chapter 1



Using Conversion Factors





Converting Units

Sample Problem A

Convert 0.851 L to milliliters.

Chapter 1



Sample Problem A Solution

• The equality that links the two units is 1000 mL = 1 L. (The prefix milli- represents 1/1000 of a base unit.)

• The conversion factor needed must cancel liters and leave milliliters. Thus, liters must be on the bottom of the fraction and milliliters must be on the top.

1000 mL

1 L

1000 mL? mL = 0.851 L × =

1 L851 mL




Derived Units

• Many quantities you can measure need units other than the seven basic SI units.

• These units are derived by multiplying or dividing the base units.

• Speed is distance divided by time.The derived unit of speed is meters per second (m/s).

• A rectangle’s area is found by multiplying its length (in meters) by its width (also in meters).

• Its unit is square meters (m2).




Derived Units, continued

• Volume is another commonly used derived unit.

• The volume of a book can be found by multiplying its length, width, and height.

• The unit of volume is the cubic meter (m3).

• This unit is too large and inconvenient in most labs. Chemists usually use the liter (L).

1L = 1000 mL = 1000 cm3




Properties of MatterPhysical Properties

• A physical property of a substance is a characteristic that does not involve a chemical change.

• Physical properties of a substance can be determined without changing the nature of a substance.

• Physical properties include texture, state, melting point, and boiling point.




Properties of Matter, continuedDensity is the Ratio of Mass to Volume

• The density of an object is the mass of the object divided by volume of the object.

• Densities are expressed in derived units such as g/cm3 or g/mL.

• Density is calculated as follows:


mass mdensity D

volume v or

Chapter 1



Properties of Matter, continuedDensity of an Object

• The density of a substance is the same no mater what the size of the sample is.




Visual Concepts

Equation for Density

Chapter 1



Properties of Matter, continuedDensity Can Be Used to Identify Substances

• Because the density of a substance is the same for all samples, you can use this property to help identify substances.




Properties of Matter, continued Chemical Properties

• A chemical property a property of matter that describes a substance’s ability to participate in chemical reactions.

• A chemical property of many substances is that they react with oxygen.

• example: rusting

• Some substances break down into new substances when heated.




Visual Concepts

Comparing Physical and Chemical Properties

Chapter 1



Visual Concepts

Signs of a Chemical Reaction

Chapter 1



Classifying Matter

• An atom is the smallest unit of an element that maintains the properties of that element.

• Matter exists in many different forms but there are only 110 types of atoms.

• Atoms are joined together to make up all the different kinds of matter.

Section 3 How Is Matter Classified?Chapter 1



Pure Substances

• A pure substance is a sample of matter, either a single element or a single compound, that has definite chemical and physical properties.

• Elements are pure substances that only contain one kind of matter. They cannot be separated or broken down into simpler substances by chemical means.

• Each element has its own unique set of physical and chemical properties.




Pure Substances




Elements are Pure Substances

• Each elements is represented by a distinct chemical symbol.




Pure Substances, continuedElements as Single Elements or Molecules

• A molecule is the smallest unit of a substance that keeps all of the physical and chemical properties of that substance.

• A molecule usually consists of two or more atoms combined in a definite ratio.

• Diatomic elements exist as two atoms of the same element joined together.




Pure Substances, continuedSome Elements Have More Than One Form

• Some elements, such as oxygen, phosphorus, sulfur, and carbon, have many different molecular forms.

• An allotrope is one of a number of different molecular forms of an element.

• The properties of allotropes vary widely.




Pure Substances, continuedSome Elements Have More Than One Form, continued

• Oxygen exists as allotropes.

• Oxygen gas (O2) is colorless and odorless.

• Ozone (O3) is toxic and pale blue.




Pure Substances, continued Compounds are Pure Substances

• Pure substances that are not elements are compounds. Compounds are composed of more than one kind of atom.

• example: carbon dioxide (CO2)

• There may be easier ways of preparing them, but compounds can be made from their elements.

• Compounds can be broken down into their elements, though often with great difficulty.




Pure Substances, continued Compounds are Represented by Formulas

• Because every molecule of a compound is made up of the same kinds of atoms arranged the same way, a compound has characteristic properties and composition.

• Compounds can be represented by an abbreviation or formula.

• A formula has subscripts which represent the ratio of different atoms in the compound.

• example: H2O has 2 hydrogen atoms and one oxygen atom




Pure Substances, continued Compounds are Represented by Formulas, continued

• Molecular formulas give information only about what makes up a compound.

• example: the molecular formula for aspirin is C9H8O4

• A structural formula shows how the atoms are connected

• This two-dimensional model does not show the molecule’s true shape.





• A ball-and-stick model shows the distances between atoms and the angles between them in three dimensions.

• A space-filling model attempts to represent the actual sizes of the atoms and not just their relative positions.

• A hand-held model can provide more information than models shown on the flat surface of the page.





• These models convey different information about acetylsalicylic acid (aspirin).




Mixtures

• A mixture is a combination of two or more substances that are not chemically combined.

• Air is a mixture of mostly nitrogen and oxygen.

• All the different gases in air are physically mixed.

• The proportions of the gases can vary.

• Water is not a mixture.

• The H and O atoms are chemically bonded

• The ratio of H to O atoms is always 2 to 1.




Mixtures, continuedMixtures Can Vary in Composition and Properties

• The proportion of the materials in a mixture can change.

• The properties of the mixture may vary.

• An alloy is a solid mixture.

• example: An alloy of gold and other metal atoms is stronger than pure gold.

• 18-karat gold contains 18 grams of gold per24 grams of alloy.

• 14-karat gold contains 14 grams of gold per24 grams of alloy.




Particle Models for Gold and Gold Alloy

Chapter 1



Mixtures, continuedHomogenous Mixtures

• A homogenous mixture describes something that has uniform structure or composition throughout.

• examples: gasoline, syrup, and air

• Because any two samples of a homogenous mixture will have the same proportions of ingredients, homogenous mixtures have the same properties throughout.




Mixtures, continuedHeterogeneous Mixtures

• A heterogeneous mixture describes something that is composed of dissimilar components.

• example: A mixture of sand and water is a heterogenous mixture.

• Any two samples of a heterogeneous mixture will have the different proportions of ingredients.

• Heterogeneous mixtures have different properties throughout.




Examples of Mixtures

• Mixtures are either homogenous or heterogeneous.




Types of Mixtures

Chapter 1 Section 3 How Is Matter Classified?



Mixtures, continuedDistinguishing Mixtures from Compounds

• The properties of a mixture reflect the properties of the substances it contains.

• The properties of a compound often are very different from the properties of the elements that make it up.

• A mixture’s components can be present in varying proportions.

• A compound has a definite composition in terms of the masses of its elements.




Classifying Matter

Chapter 1 Section 3 How Is Matter Classified?



1. Which of the following is best classified as a homogeneous mixture?

A. blood

B. copper wire

C. pizza

D. hot tea

Standardized Test Preparation

Understanding Concepts

Chapter 1



1. Which of the following is best classified as a homogeneous mixture?

A. blood

B. copper wire

C. pizza

D. hot tea



Chapter 1



2. Which of the following statements about compounds is true?

F. A compound contains only one element.

G. A compound can be classified as either heterogeneous or homogeneous.

H. A compound has a defined ratio by mass of the elements that it contains.

I. A compound varies in chemical composition depending on the sample size.



Chapter 1



2. Which of the following statements about compounds is true?

F. A compound contains only one element.

G. A compound can be classified as either heterogeneous or homogeneous.

H. A compound has a defined ratio by mass of the elements that it contains.

I. A compound varies in chemical composition depending on the sample size.



Chapter 1



3. Which of the following is an element?

A. BaCl2

B. CO

C. He

D. NaOH



Chapter 1



3. Which of the following is an element?

A. BaCl2

B. CO

C. He

D. NaOH



Chapter 1



4. Is photosynthesis, in which light energy is captured by plants to make sugar from carbon dioxide and water, a physical change or a chemical change? Explain your answer.



Chapter 1



4. Is photosynthesis, in which light energy is captured by plants to make sugar from carbon dioxide and water, a physical change or a chemical change? Explain your answer.

Answer: Photosynthesis is a chemical change because the products of the change are different substances than the starting materials.



Chapter 1



5. A student checks the volume, melting point, and shape of two unlabeled samples of matter and finds that the measurements are identical. He concludes that the samples have the same chemical composition. Is this a valid conclusion? What additional information might be collected to test this conclusion?



Chapter 1



5. A student checks the volume, melting point, and shape of two unlabeled samples of matter and finds that the measurements are identical. He concludes that the samples have the same chemical composition. Is this a valid conclusion? What additional information might be collected to test this conclusion?

Answer: The conclusion is not valid because volume and shape give no information about identity and two different substances can have the same melting point. Additional information could include determining additional physical properties or chemical properties.



Chapter 1



6. Describe the physical and chemical changes that occur when a pot of water is boiled over a campfire.



Chapter 1



6. Describe the physical and chemical changes that occur when a pot of water is boiled over a campfire.

Answer: A physical change is the conversion of liquid water to vapor. A chemical change is the reaction between wood and oxygen that generates heat while forming carbon dioxide and ash.



Chapter 1



Read the passage below. Then answer the questions.

Willow bark has been a remedy for pain and fever for hundreds of years. In the late eighteenth century, scientists isolated the compound in willow bark that is responsible for its effects. They then converted it to a similar compound, salicylic acid, which is even more effective. In the late nineteenth century, a German chemist, Felix Hoffmann, did research to find a pain reliever that would help his father’s arthritis, but not cause the nausea that is a side effect of salicylic acid. Because the technologies used to synthesize chemicals had improved, he had a number of more effective ways the work with chemical compounds than the earlier chemists. The compound that he made, acetylsalicylic acid, is known as aspirin. It is still one of the most common pain relievers more than 100 years later.

Reading Skills

Standardized Test PreparationChapter 1



7. The main reason willow bark has been used as a painkiller and fever treatment is because

F. chemists can use it to make painkilling compounds.

G. it contains elements that have painkilling effects.

H. it contains compounds that have painkilling effects.

I. no other painkillers were available long ago.

Reading Skills




7. The main reason willow bark has been used as a painkiller and fever treatment is because

F. chemists can use it to make painkilling compounds.

G. it contains elements that have painkilling effects.

H. it contains compounds that have painkilling effects.

I. no other painkillers were available long ago.

Reading Skills




8. Why is aspirin normally used as a painkiller instead of salicylic acid?

A. Aspirin tends to cause less nausea.

B. Aspirin is cheaper to make than salicylic acid.

C. Only aspirin can be isolated from willow bark.

D. Salicylic acid is less effective as a painkiller.

Reading Skills




8. Why is aspirin normally used as a painkiller instead of salicylic acid?

A. Aspirin tends to cause less nausea.

B. Aspirin is cheaper to make than salicylic acid.

C. Only aspirin can be isolated from willow bark.

D. Salicylic acid is less effective as a painkiller.

Reading Skills




The table and graph below show a relationship of direct

proportionality between mass (grams) versus volume (cubic

centimeters). Use it to answer questions 9 through 12.

Interpreting Graphics




9. Based on information in the table and the graph, what is the relationship between mass and volume of a sample of aluminum?

F. no relationship

G. a linear relationship

H. an inverse relationship

I. an exponential relationship





9. Based on information in the table and the graph, what is the relationship between mass and volume of a sample of aluminum?

F. no relationship

G. a linear relationship

H. an inverse relationship

I. an exponential relationship





10. From the data provided, what is the density of aluminum?

A. 0.37 g/cm3

B. 1.0 g/cm3

C. 2.0 g/cm3

D. 2.7 g/cm3





10. From the data provided, what is the density of aluminum?

A. 0.37 g/cm3

B. 1.0 g/cm3

C. 2.0 g/cm3

D. 2.7 g/cm3





11. Someone gives you a metal cube that measures 2.0 centimeters on each side and has a mass of 27.5 grams. What can be deduced about the metal from this information and the table?

F. It is not pure aluminum.

G. It has more than one element.

H. It does not contain any aluminum.

I. It is a compound, not an element.





11. Someone gives you a metal cube that measures 2.0 centimeters on each side and has a mass of 27.5 grams. What can be deduced about the metal from this information and the table?

F. It is not pure aluminum.

G. It has more than one element.

H. It does not contain any aluminum.

I. It is a compound, not an element.





12.The density of nickel is 8.90 g/cm3. How could this information be applied, along with information from the graph, to determine which of two pieces of metal is aluminum, and which is nickel?





12.The density of nickel is 8.90 g/cm3. How could this information be applied, along with information from the graph, to determine which of two pieces of metal is aluminum, and which is nickel?

Answer: From the table, you can calculate the density of aluminum. Aluminum is much less dense than nickel, so if the pieces of metal are the same size, the lighter one is aluminum.



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