ChemistryChemistry

Chapter 1.4Chapter 1.4

CompoundsCompounds

What is a compound?What is a compound?

Pure substance composed of atoms of two or more Pure substance composed of atoms of two or more different elementsdifferent elements

What are the two types of compounds?What are the two types of compounds?

Covalent and ionic compoundsCovalent and ionic compounds

Covalent CompoundsCovalent Compounds

The smallest particle of a covalent compound The smallest particle of a covalent compound that has the properties of the compound is a that has the properties of the compound is a ___________.___________.

MoleculeMolecule

Examples:Examples: Water, sugar, and oxygenWater, sugar, and oxygen

Ionic CompoundsIonic Compounds

An _______ is an atom or group of atoms with An _______ is an atom or group of atoms with an __________ _________.an __________ _________.

Ion, Ion, Electrical chargeElectrical charge

Example:Example: Table Salt NaTable Salt Na++ and Cl and Cl--

CompoundsCompounds

Compounds are:Compounds are:

Pure substancesPure substances Have a unique set of chemical propertiesHave a unique set of chemical properties Have a unique set of physical propertiesHave a unique set of physical properties

CompoundsCompounds

Acetic AcidAcetic Acid

The term acid indicates that it belongs to a group The term acid indicates that it belongs to a group of compounds with similar chemical propertiesof compounds with similar chemical properties

Acids all have a pH of less than 7Acids all have a pH of less than 7 Can be strong or weakCan be strong or weak

CompoundsCompounds

pH:pH: The degree to which an aqueous solution of The degree to which an aqueous solution of

compound shows the properties of an acidcompound shows the properties of an acid

In water, acids have a pH of less than 7In water, acids have a pH of less than 7

Aspirin when dissolved in water has a pH of 2.7Aspirin when dissolved in water has a pH of 2.7

CompoundsCompounds

Base:Base:

A compound that when dissolved in water has a A compound that when dissolved in water has a pH greater than 7pH greater than 7

Some of the properties of bases are opposite of the Some of the properties of bases are opposite of the properties of acidsproperties of acids

CompoundsCompounds

If we don’t know the pH of an aqueous If we don’t know the pH of an aqueous solution how do you think we would figure it solution how do you think we would figure it out?out?

Use a pH meterUse a pH meter IndicatorsIndicators

The color of the indicator will change to indicate if it is The color of the indicator will change to indicate if it is an acid or a basean acid or a base

Water solutions of acids….Water solutions of acids…. Water solutions of bases …Water solutions of bases …

Taste sourTaste sour Taste bitter and feel Taste bitter and feel slipperyslippery

Turn blue pH paper redTurn blue pH paper red Turn red pH paper blueTurn red pH paper blue

Have pH values less than 7Have pH values less than 7 Have pH values greater Have pH values greater than 7than 7

React with bases and React with bases and certain metals to form saltscertain metals to form salts

React with acids to form React with acids to form saltssalts

Organic or InorganicOrganic or Inorganic

What is the difference between an organic What is the difference between an organic compound and an inorganic compound?compound and an inorganic compound?

Compounds that contain carbon are organic Compounds that contain carbon are organic compounds.compounds.

There are a few exceptionsThere are a few exceptions

Compounds that do not contain carbon are Compounds that do not contain carbon are inorganic compoundsinorganic compounds

FormulasFormulas

There are 4 different ways to represent compoundsThere are 4 different ways to represent compounds

1.1. Molecular formula:Molecular formula: CC99HH88OO44

Shows the number of atoms of each element present in a Shows the number of atoms of each element present in a molecule molecule

Does not show how they are bonded thoughDoes not show how they are bonded though

FormulasFormulas

2. Structural Formula2. Structural Formula

Shows the exact number of atoms present in a Shows the exact number of atoms present in a moleculemolecule

Shows how the atoms are bonded together Shows how the atoms are bonded together

The lines represent the bonds between atomsThe lines represent the bonds between atoms

Structural FormulaStructural Formula

FormulasFormulas

3. Ball-and-stick model3. Ball-and-stick model

Show the geometric Show the geometric arrangement of atoms in arrangement of atoms in a formulaa formula

Acetic Acid

FormulasFormulas

4. Space-fill model4. Space-fill model

Shows the geometric Shows the geometric arrangementarrangement

Most closely represents Most closely represents the actual shape of the the actual shape of the moleculemolecule

FormulasFormulas

Look at Figure 1-21 in your text (page 28)Look at Figure 1-21 in your text (page 28)

What do all three structural formulas have in What do all three structural formulas have in common?common?

What is unique about acetaminophen?What is unique about acetaminophen?

MixturesMixtures

What is a mixture?What is a mixture? Collection of two or more pure substances Collection of two or more pure substances

physically mixed togetherphysically mixed together

The proportions of different substances in a The proportions of different substances in a mixture can varymixture can vary Ex: Chicken soup Ex: Chicken soup

MixturesMixtures

The properties of a mixture can vary:The properties of a mixture can vary:

Pure gold is 24-karat gold because it is too soft to keep its Pure gold is 24-karat gold because it is too soft to keep its shape in jewelry it is mixed with other metals to give it shape in jewelry it is mixed with other metals to give it more strengthmore strength

Gold alloy is used to make 18-karat goldGold alloy is used to make 18-karat gold It is 18 parts gold out of 24 parts totalIt is 18 parts gold out of 24 parts total

For even greater hardness they also make a 14-karat goldFor even greater hardness they also make a 14-karat gold

MixturesMixtures

Homogeneous mixture:Homogeneous mixture:

All the components are uniformly distributed at the All the components are uniformly distributed at the microscopic levelmicroscopic level

Gasoline, syrup, air, and 18-karat gold are all Gasoline, syrup, air, and 18-karat gold are all homogeneoushomogeneous

All regions of the mixture are identical in their All regions of the mixture are identical in their composition and propertiescomposition and properties

MixturesMixtures

Homogeneous mixture:Homogeneous mixture:

The most common type of homogeneous mixture The most common type of homogeneous mixture is a ____________.is a ____________.

SolutionSolution

Example: Vinegar, tea, and salt water Example: Vinegar, tea, and salt water

MixturesMixtures

Heterogeneous mixture:Heterogeneous mixture:

Contains substances that are not evenly distributed.Contains substances that are not evenly distributed.

Some regions have different properties in the Some regions have different properties in the mixture than others.mixture than others.

HeterogeneousHeterogeneous HomogeneousHomogeneousOrange juice or tomato juiceOrange juice or tomato juice: : Uneven distribution of components. Uneven distribution of components. Settles out upon standing.Settles out upon standing.

Iced teaIced tea: Uniform distribution of : Uniform distribution of components. Components can not be components. Components can not be filtered out. Will not settle outfiltered out. Will not settle out

Chocolate chip pecan cookie: Chocolate chip pecan cookie: Uneven distribution of componentsUneven distribution of components

Stainless steelStainless steel: Even distribution of : Even distribution of componentscomponents

Granite: Granite: Uneven distribution of Uneven distribution of componentscomponents

Carbonated beverage: Carbonated beverage: Uniform Uniform distribution of componentsdistribution of components

Salad: Salad: Can be easily separated by Can be easily separated by physical meansphysical means

Maple syrup: Maple syrup: Components cannot be Components cannot be filtered out and will not settle upon filtered out and will not settle upon standingstanding

Mixtures vs. CompoundsMixtures vs. Compounds

2 principal differences:2 principal differences:

1.1. The properties of the mixture reflect the The properties of the mixture reflect the properties of the substances it contains, but the properties of the substances it contains, but the properties of a compound often bear no properties of a compound often bear no resemblance to the properties of the elements that resemblance to the properties of the elements that compose it.compose it.

Mixtures vs. CompoundsMixtures vs. Compounds

2 Principal differences2 Principal differences

2.2. Compounds have definite composition by mass Compounds have definite composition by mass of their combining elements, while the of their combining elements, while the components of mixtures may be present in components of mixtures may be present in varying proportions.varying proportions.

MixturesMixtures

How would you go about separating chemical How would you go about separating chemical mixtures?mixtures?

React the mixture to form a substance that can React the mixture to form a substance that can easily be removed by filtrationeasily be removed by filtration

When is a Substance Pure?When is a Substance Pure?

Is water that you drink from the tap pure? How Is water that you drink from the tap pure? How about bottled water?about bottled water? The answer is most likely no for both because they The answer is most likely no for both because they

have minerals which are considered impurities. have minerals which are considered impurities.

Are chemicals in the stockroom pure?Are chemicals in the stockroom pure? They most likely also contain impurities They most likely also contain impurities Standards for chemical purity have been Standards for chemical purity have been

established to control for impuritiesestablished to control for impurities

When is a substance pure?When is a substance pure?

Figure 1-23Figure 1-23

Primary-standard chemicals are of a higher Primary-standard chemicals are of a higher purity than reagent-gradepurity than reagent-grade

Commercial or technical grade chemicals are Commercial or technical grade chemicals are less expensive and because we don’t need less expensive and because we don’t need high-purity chemicals for our experimentshigh-purity chemicals for our experiments

Figure 1-24Figure 1-24

Go through the figure together!Go through the figure together!

Review QuestionsReview Questions

Questions 1-5Questions 1-5

Questions 8-9Questions 8-9

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