Chemistry Chapter 1.4

Compounds What is a compound? What is a compound? Pure substance composed of atoms of two or more different elements Pure substance composed of atoms of two or more different elements What are the two types of compounds? What are the two types of compounds? Covalent and ionic compounds Covalent and ionic compounds

Covalent Compounds The smallest particle of a covalent compound that has the properties of the compound is a ___________. The smallest particle of a covalent compound that has the properties of the compound is a ___________. Molecule Molecule Examples: Examples: Water, sugar, and oxygen Water, sugar, and oxygen

Ionic Compounds An _______ is an atom or group of atoms with an __________ _________. An _______ is an atom or group of atoms with an __________ _________. Ion, Ion, Electrical charge Electrical charge Example: Example: Table Salt Na + and Cl - Table Salt Na + and Cl -

Compounds Compounds are: Compounds are: Pure substances Pure substances Have a unique set of chemical properties Have a unique set of chemical properties Have a unique set of physical properties Have a unique set of physical properties

Compounds Acetic Acid Acetic Acid The term acid indicates that it belongs to a group of compounds with similar chemical properties The term acid indicates that it belongs to a group of compounds with similar chemical properties Acids all have a pH of less than 7 Acids all have a pH of less than 7 Can be strong or weak Can be strong or weak

Compounds pH: pH: The degree to which an aqueous solution of compound shows the properties of an acid The degree to which an aqueous solution of compound shows the properties of an acid In water, acids have a pH of less than 7 In water, acids have a pH of less than 7 Aspirin when dissolved in water has a pH of 2.7 Aspirin when dissolved in water has a pH of 2.7

Compounds Base: Base: A compound that when dissolved in water has a pH greater than 7 A compound that when dissolved in water has a pH greater than 7 Some of the properties of bases are opposite of the properties of acids Some of the properties of bases are opposite of the properties of acids

Compounds If we don’t know the pH of an aqueous solution how do you think we would figure it out? If we don’t know the pH of an aqueous solution how do you think we would figure it out? Use a pH meter Use a pH meter Indicators Indicators The color of the indicator will change to indicate if it is an acid or a base The color of the indicator will change to indicate if it is an acid or a base

Water solutions of acids…. Water solutions of bases … Taste sour Taste bitter and feel slippery Turn blue pH paper red Turn red pH paper blue Have pH values less than 7 Have pH values greater than 7 React with bases and certain metals to form salts React with acids to form salts

Organic or Inorganic What is the difference between an organic compound and an inorganic compound? What is the difference between an organic compound and an inorganic compound? Compounds that contain carbon are organic compounds. Compounds that contain carbon are organic compounds. There are a few exceptions There are a few exceptions Compounds that do not contain carbon are inorganic compounds Compounds that do not contain carbon are inorganic compounds

Formulas There are 4 different ways to represent compounds There are 4 different ways to represent compounds 1. Molecular formula: C 9 H 8 O 4 C 9 H 8 O 4 Shows the number of atoms of each element present in a molecule Shows the number of atoms of each element present in a molecule Does not show how they are bonded though Does not show how they are bonded though

Formulas 2. Structural Formula Shows the exact number of atoms present in a molecule Shows the exact number of atoms present in a molecule Shows how the atoms are bonded together Shows how the atoms are bonded together The lines represent the bonds between atoms The lines represent the bonds between atoms

Structural Formula

Formulas 3. Ball-and-stick model Show the geometric arrangement of atoms in a formula Show the geometric arrangement of atoms in a formula Acetic Acid

Formulas 4. Space-fill model Shows the geometric arrangement Shows the geometric arrangement Most closely represents the actual shape of the molecule Most closely represents the actual shape of the molecule

Formulas 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 common? What do all three structural formulas have in common? What is unique about acetaminophen? What is unique about acetaminophen?

Mixtures What is a mixture? What is a mixture? Collection of two or more pure substances physically mixed together Collection of two or more pure substances physically mixed together The proportions of different substances in a mixture can vary The proportions of different substances in a mixture can vary Ex: Chicken soup Ex: Chicken soup

Mixtures 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 shape in jewelry it is mixed with other metals to give it more strength 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 more strength Gold alloy is used to make 18-karat gold Gold alloy is used to make 18-karat gold It is 18 parts gold out of 24 parts total It is 18 parts gold out of 24 parts total For even greater hardness they also make a 14-karat gold For even greater hardness they also make a 14-karat gold

Mixtures Homogeneous mixture: Homogeneous mixture: All the components are uniformly distributed at the microscopic level All the components are uniformly distributed at the microscopic level Gasoline, syrup, air, and 18-karat gold are all homogeneous Gasoline, syrup, air, and 18-karat gold are all homogeneous All regions of the mixture are identical in their composition and properties All regions of the mixture are identical in their composition and properties

Mixtures Homogeneous mixture: Homogeneous mixture: The most common type of homogeneous mixture is a ____________. The most common type of homogeneous mixture is a ____________. Solution Solution Example: Vinegar, tea, and salt water Example: Vinegar, tea, and salt water

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

HeterogeneousHomogeneous Orange juice or tomato juice: Uneven distribution of components. Settles out upon standing. Iced tea: Uniform distribution of components. Components can not be filtered out. Will not settle out Chocolate chip pecan cookie: Uneven distribution of components Stainless steel: Even distribution of components Granite: Uneven distribution of components Carbonated beverage: Uniform distribution of components Salad: Can be easily separated by physical means Maple syrup: Components cannot be filtered out and will not settle upon standing

Mixtures vs. Compounds 2 principal differences: 2 principal differences: 1. The properties of the mixture reflect the properties of the substances it contains, but the properties of a compound often bear no resemblance to the properties of the elements that compose it.

Mixtures vs. Compounds 2 Principal differences 2 Principal differences 2. Compounds have definite composition by mass of their combining elements, while the components of mixtures may be present in varying proportions.

Mixtures How would you go about separating chemical mixtures? How would you go about separating chemical mixtures? React the mixture to form a substance that can easily be removed by filtration React the mixture to form a substance that can easily be removed by filtration

When is a Substance Pure? Is water that you drink from the tap pure? How about bottled water? Is water that you drink from the tap pure? How about bottled water? The answer is most likely no for both because they have minerals which are considered impurities. The answer is most likely no for both because they 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 established to control for impurities Standards for chemical purity have been established to control for impurities

When is a substance pure? Figure 1-23 Figure 1-23 Primary-standard chemicals are of a higher purity than reagent-grade Primary-standard chemicals are of a higher purity than reagent-grade Commercial or technical grade chemicals are less expensive and because we don’t need high-purity chemicals for our experiments Commercial or technical grade chemicals are less expensive and because we don’t need high-purity chemicals for our experiments

Figure 1-24 Go through the figure together! Go through the figure together!

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