CHEM 1305 Introductory Chemistry

Transcription

1 CHEM 1305 Introductory Chemistry Introductory Chemistry: Concepts and Critical Thinking 7 th Edition, Charles H. Corwin Chapter 3. Matter and Energy Modified by: Dr. Violeta F. Coarfa

2 Classification of Matter Dr. Coarfa - Chem1305 CHEMISTRY study of matter Matter anything that has mass and occupies volume Matter Pure substances (a single form of mater) silver, gold, water, table salt Separated physically Mixtures (two or more substances mixed) air, brass, dental filling, vinegar Elements (only one type of atom) Ag, Au, Cu Compounds (two or more elements) water, table salt Law of constant composition Homogeneous (uniform composition = solutions) water + salt (solutions), brass, air Solutions: - aqueous: table salt - water - non-aqueous: gasoline - grease - solid: brass; liquid: beer; gas: air Heterogeneous water + sand; oil + water

3 Mixtures Definitions A mixture is a combination of two or more substances in which the substances retain their distinct identities. Homogenous mixture (solution) composition of the mixture is the same throughout. 24-K gold the element 18-K and 14-K alloys Heterogeneous mixture composition is not uniform throughout. cement, iron filings in sand

4 Learning Check Consider the following properties of the element copper: a. Copper metal cannot be broken down by a chemical change. b. Copper reacts with oxygen in air to give copper (II) oxide. c. Copper, in the form of malachite ore, is found worldwide. d. Copper and tin compose bronze alloy. Classify each of the following copper samples as an element, a compound, a homogeneous mixture, or a heterogeneous mixture: a. copper wire b. copper oxide c. malachite ore d. bronze alloy Dr. Coarfa - Chem1305

5 Learning Check Solution Classify each of the following copper samples as an element, a compound, a homogeneous mixture, or a heterogeneous mixture: a. copper wire Element b. copper oxide Compound c. malachite ore Heterogeneous mixture d. bronze alloy Homogeneous mixture malachite bronze star Dr. Coarfa - Chem1305

6 Learning Check Consider the following properties of the element copper: a. Mercury liquid cannot be broken down by a chemical change. b. Mercury (II) oxide can be heated to give mercury and oxygen gas. c. Mercury, in form of cinnabar ore, is found in Spain and Italy. d. Mercury and silver compose the alloy used for dental fillings. Classify each of the following mercury samples as an element, a compound, a homogeneous mixture, or a heterogeneous mixture: a. mercury liquid b. mercury (II) oxide c. cinnabar ore d. dental alloy Dr. Coarfa - Chem1305

7 Learning Check Solution Classify each of the following mercury samples as an element, a compound, a homogeneous mixture, or a heterogeneous mixture: a. mercury liquid Element b. Mercury (II) oxide Compound c. cinnabar ore Heterogeneous mixture d. dental alloy Homogeneous mixture cinnabar ore mercury liquid Mercury (II) oxide dental alloy Dr. Coarfa - Chem1305

8 Physical States of Matter Most substances can exist as either a solid, liquid, or gas. Water exists as a solid below 0 C; as a liquid between 0 C and 100 C; and as a gas above 100 C. A substance can change physical states as the temperature changes. 8

9 States of Matter Solids Solid particles are tightly packed together; definite, fixed shape Cannot be compressed; definite volume (constant) Have the least energy of the three states of matter Liquids definite volume but indefinite shape (they have the shape of the container) Liquid particles are loosely packed and are free to move past one another Cannot be compressed Have more energy than solids but less energy than gasses Gases indefinite shape and volume Large average distances between particles Little attraction between particles Constant collisions between particles, leading to constant changes in direction and velocity Have the most energy of the three states of matter

10 Physical Transformations Dr. Coarfa - Chem1305

11 Learning Check State the term that applies to each of the following changes of physical state: a. Snow changes from a solid to a liquid. b. Gasoline changes from a liquid to a gas. c. Dry ice changes from a solid to a gas. d. A refrigerant changes from a gas to a liquid. e. Water changes from a liquid to a solid. f. Iodine vapor changes from a gas to a solid.

12 Learning Check - Solution State the term that applies to each of the following changes of physical state: a. Snow changes from a solid to a liquid. Melting b. Gasoline changes from a liquid to a gas. Vaporization c. Dry ice changes from a solid to a gas. Sublimation d. A refrigerant changes from a gas to a liquid. Condensation e. Water changes from a liquid to a solid. Freezing f. Iodine vapor changes from a gas to a solid. Deposition

13 Elements and Symbols of Elements An element is a substance that cannot be separated into simpler substances by chemical means. over 100 elements that occur in nature 82 elements are stable only 10 elements account for more than 95% of the mass of Earth s crust

14 Elements In the Human Body Oxygen is the most common element in both the Earth s crust and in the human body. While silicon is the second most abundant element in the crust, carbon is the second most abundant in the body.

15 Periodic Table Group Numbers A main groups (long groups) B secondary groups (short groups) also called transition groups Note: Semimetals or Metalloids Dr. Coarfa - Chem1305

16 Periodic Table Group Names Noble Gases Alkali Metals Alkaline Earth Metals Halogens

17 Names of the Elements Each element has a unique name: sodium, calcium, chlorine Names have several origins: Hydrogen is derived from Greek. Carbon is derived from Latin. Curium is named for Marie Curie. Nobelium is named for Alfred Nobel. Element Symbols Each element is abbreviated using a chemical symbol. The symbols are one or two letters long. Most of the time, the symbol is derived from the name of the element. - C is the symbol for carbon. - Cd is the symbol for cadmium. When a symbol has two letters, the first is capitalized and the second is lowercase.

18 Memorize the elements above and also the rest of elements from main groups, which are not listed above! Dr. Coarfa - Chem1305

19 Learning Check Select the correct symbol for each. A. Calcium 1) C 2) Ca 3) CA B. Sulfur 1) S 2) Sl 3) Su C. Iron 1) Ir 2) FE 3) Fe

20 Learning Check - Solution Select the correct symbol for each. A. Calcium 2) Ca B. Sulfur 1) S C. Iron 3) Fe Dr. Coarfa - Chem1305

21 Learning Check Select the correct name for each symbol. A. N 1) neon 2) nitrogen 3) nickel B. P 1) potassium 2) phlogiston 3) phosphorus C. Ag 1) silver 2) agean 3) gold

22 Learning Check - Solution Select the correct name for each: A. N 2) nitrogen B. P 3) phosphorus C. Ag 1) silver Dr. Coarfa - Chem1305

23 Learning Check Identify the element described by the following: A. Group 7A (17), Period 4 1) Br 2) Cl 3) Mn B. Group 2A (2), Period 3 1) beryllium 2) boron 3) magnesium C. Group 5A (15), Period 2 1) phosphorus 2) arsenic 3) nitrogen

24 Learning Check - Solution Identify the element described by the following: A. Group 7A (17), Period 4 1) Br 2) Cl 3) Mn B. Group 2A (2), Period 3 1) beryllium 2) boron 3) magnesium C. Group 5A (15), Period 2 1) phosphorus 2) arsenic 3) nitrogen

25 1. Metals 2. Nonmetals Types of Elements Elements can be divided into three classes: 3. Semimetals or metalloids - properties midway between those of metals and nonmetals.

26 Metal Properties Metals are typically solids with high melting points and high densities and have a bright, metallic luster. Metals are good conductors of heat and electricity. Metals can be hammered into thin sheets and are said to be malleable. Metals can be drawn into fine wires and are said to be ductile. Nonmetal Properties Nonmetals typically have low melting points and low densities and have a dull appearance. Nonmetals are poor conductors of heat and electricity. Nonmetals are not malleable or ductile and crush into a powder when hammered. 11 nonmetals occur naturally in the gaseous state.

27 Summary of Properties Dr. Coarfa - Chem1305

28 Learning Check Which of the following properties is not characteristic of a metal? a. good conductor of heat b. malleable c. high melting point d. reacts with other metals Solution: Refer to Table 3.4 to classify each of the following properties: a. Metals are good conductors of heat. b. Metals are malleable. c. Metals usually have high melting points. d. Metals do not react with other metals; they mix to form alloys.

29 Learning Check Q1. Which of the following properties is NOT a characteristic of the Group 1A(1) elements (alkali metals)? A) They are shiny. B) They are good conductors of heat. C) They react vigorously with water. D) Most of them are liquids at room temperature. E) They are good conductors of electricity. Q2. The Group 8A(18) elements A) are unreactive and are rarely found in combination with other elements. B) are good conductors of electricity. C) melt at high temperatures. D) are liquids at room temperature. E) react vigorously with water. Dr. Coarfa - Chem1305

30 Learning Check - Solution Q1. Which of the following properties is NOT a characteristic of the Group 1A(1) elements (alkali metals)? A) They are shiny. B) They are good conductors of heat. C) They react vigorously with water. D) Most of them are liquids at room temperature. E) They are good conductors of electricity. Q2. The Group 8A(18) elements A) are unreactive and are rarely found in combination with other elements. B) are good conductors of electricity. C) melt at high temperatures. D) are liquids at room temperature. E) react vigorously with water. Dr. Coarfa - Chem1305

31 Periodic Table of the Elements Each element is assigned a number to identify it. It is called the atomic number. Hydrogen s atomic number is 1; helium is 2; up to uranium, which is 92. The elements are arranged by atomic number on the periodic table. -> Metals - of main groups - of secondary groups (Transition metals) - inner transition metals -> Nonmetals (only in main groups)

32 Solid, Liquid, and Gaseous Elements Dr. Coarfa - Chem1305

33 Learning Check Identify each of the following elements as 1) metal, 2) nonmetal, or 3) metalloid. A. sodium B. chlorine C. silicon D. iron E. carbon F. aluminium Dr. Coarfa - Chem1305

34 Learning Check - Solution Identify each of the following elements as 1) metal, 2) nonmetal, or 3) metalloid. A. sodium (1) B. chlorine (2) C. silicon (3) D. iron (1) E. carbon (2) F. aluminium (1) Dr. Coarfa - Chem1305

35 Learning Check Match the elements to the description. A. Metals in Group 4A (14) 1) Sn, Pb 2) C, Si 3) C, Si, Ge, Sn B. Nonmetals in Group 5A (15) 1) As, Sb, Bi 2) N, P 3) N, P, As, Sb C. Metalloids in Group 4A (14) 1) C, Si, Ge, 2) Si, Ge 3) Si, Ge, Sn, Pb

36 Learning Check Match the elements to the description. A. Metals in Group 4A (14) 1) Sn, Pb 2) C, Si 3) C, Si, Ge, Sn B. Nonmetals in Group 5A (15) 1) As, Sb, Bi 2) N, P 3) N, P, As, Sb C. Metalloids in Group 4A (14) 1) C, Si, Ge, 2) Si, Ge 3) Si, Ge, Sn, Pb

37 Law of Definite Composition Compounds = two or more elements held together by special forces (chemical bonds) The law of definite composition states that Compounds always contain the same elements in a constant proportion by mass. E.g.: Water, H 2 O, is always 11.19% hydrogen and 88.81% oxygen by mass, no matter what its source.

38 Chemical Formulas A unit of matter (particle) composed of two or more nonmetal atoms is a molecule. A chemical formula expresses the number and types of atoms in a molecule. The chemical formula of sulfuric acid is H 2 SO 4.

39 Writing Chemical Formulas The number of each type of atom in a molecule is indicated with a subscript in a chemical formula. If there is only one atom of a certain type, no 1 is used. A molecule of the vitamin niacin has 6 carbon atoms, 6 hydrogen atoms, 2 nitrogen atoms, and 1 oxygen atom. What is the chemical formula? C 6 H 6 N 2 O Dr. Coarfa - Chem1305

40 Ethylene glycol has a total of 10 atoms. Dr. Coarfa - Chem1305 Interpreting Chemical Formulas Some chemical formulas use parentheses to clarify atomic composition. Ethylene glycol, a component of some antifreezes, has a chemical formula of C 2 H 4 (OH) 2 2 carbon atoms 4 hydrogen atoms 2 OH units, meaning 2 H atoms and 2 O atoms Total: 2 carbon atoms, 6 hydrogen atoms and 2 oxygen atoms. How many total atoms are in ethylene glycol?

41 Learning Check Q1. State the total number of atoms in a molecule of vitamin, B 3 C 6 H 6 N 2 O. Q2. Write the chemical formula for vitamin B 6, if a molecule is composed of 8 carbon atoms, 11 hydrogen atoms, 1 nitrogen atom, and 3 oxygen atoms.

42 Learning Check - Solution Q1. State the total number of atoms in a molecule of vitamin, B 3 C 6 H 6 N 2 O. Solution: The chemical formula for vitamin B 3 indicates 6 carbon atoms, 6 hydrogen atoms, 2 nitrogen atoms, and 1 oxygen atom. Thus, C 6 H 6 N 2 O has a total of 15 atoms. Q2. Write the chemical formula for vitamin B 6, if a molecule is composed of 8 carbon atoms, 11 hydrogen atoms, 1 nitrogen atom, and 3 oxygen atoms. Solution: C 8 H 11 NO 3 (total of 23 atoms)

43 Learning Check Q1. State the total number of atoms in a molecule of glycerin, C 3 H 5 (OH) 3 Q2. Write the chemical formula for nitroglycerin if a molecule is composed of 3 carbon atoms, 5 hydrogen atoms, 3 oxygen atoms, and 3 NO 2 units.

44 Learning Check - Solution Q1. State the total number of atoms in a molecule of glycerin, C 3 H 5 (OH) 3 Solution: The chemical formula for glycerin indicates 3 carbon atoms, 5 hydrogen atoms, and 3 OH units. Thus, C 3 H 5 (OH) 3 has a total of 14 atoms. Q2. Write the chemical formula for nitroglycerin if a molecule is composed of 3 carbon atoms, 5 hydrogen atoms, 3 oxygen atoms, and 3 NO 2 units. Solution: C 3 H 5 O 3 (NO 2 ) 3 (20 atoms total)

45 Physical & Chemical Properties A physical property is a characteristic of a pure substance that we can observe without changing its composition. Examples: - appearance; physical state - melting and boiling points - density, conductivity, solubility A chemical property describes the chemical reactions of a pure substance. 45

46 Chemical Properties Sodium metal (Na) reacts with chlorine gas (Cl 2 ) to produce sodium chloride (NaCl). Dr. Coarfa - Chem1305

47 Classify each of the following as a physical property or a chemical property. a. Water appears colorless and odorless at 20 C. b. Water dissolves sugar crystals. c. Water produces a gas with calcium metal. d. Water exists as ice at 10 C. Solution: Learning Check If a reaction occurs, there is a change in composition and the property is chemical. Otherwise, the property is physical. a. Color and odor are physical properties. b. Solubility is a physical property. c. A reaction producing a gas is a chemical property. d. Physical state is a physical property. Dr. Coarfa - Chem1305

48 Learning Check Q1. Classify each of the following properties as physical or chemical. (a) Water appears colorless and odorless at 20 C. (b) Water dissolves sucrose crystals. (c) Water produces a gas with calcium metal. (d) Water exists as ice at -10 C. Q2. Classify each of the following properties as physical or chemical. (a) Water appears hard and crystalline at 0 C. (b) Water is insoluble in gasoline. (c) Water is a very weak conductor of electricity. (d) Water produces a gas with calcium metal.

49 Learning Check - Solution Q1. Classify each of the following properties as physical or chemical. (a) Water appears colorless and odorless at 20 C. (b) Water dissolves sucrose crystals. (c) Water produces a gas with calcium metal. (d) Water exists as ice at -10 C. If a reaction occurs, there is a change in composition and the property is chemical. Otherwise, the property is physical. (a) Color and odor are physical properties. (b) Solubility is a physical property. (c) A chemical reaction is a chemical property. (d) A physical state is a physical property. Q2. Classify each of the following properties as physical or chemical. (a) Water appears hard and crystalline at 0 C. (b) Water is insoluble in gasoline. (c) Water is a very weak conductor of electricity. (d) Water produces a gas with calcium metal. (a) physical; (b) physical; (c) physical; (d) chemical Dr. Coarfa - Chem1305

50 Physical and Chemical Changes A physical change is a change where the chemical composition of the sample does not change. Examples: changes in physical state/shape of a pure substance. A chemical change is a chemical reaction. The composition of the sample changes during a chemical change.

51 Evidence for Chemical Changes gas release (bubbles) light or release of heat energy formation of a precipitate a permanent color change 51

52 Learning Check Q1. Which of the following is not a physical change: A) Nitrogen freezes at -210 o C B) Water vapor condenses to form rain C) Gold melts at 1064 o C D) A puzzle is cut into 1000 pieces E) Apple slices turn brown when they are exposed to air Q2. Which of the following is a physical change: A) grinding coffee beans B) baking a cake C) converting water to hydrogen and oxygen D) digesting a cheeseburger E) burning coal

53 Learning Check - Solution Q1. Which of the following is not a physical change: A) Nitrogen freezes at -210 o C B) Water vapor condenses to form rain C) Gold melts at 1064 o C D) A puzzle is cut into 1000 pieces E) Apple slices turn brown when they are exposed to air Q2. Which of the following is a physical change: A) grinding coffee beans B) baking a cake C) converting water to hydrogen and oxygen D) digesting a cheeseburger E) burning coal

54 Learning Check Classify each of the following as a physical change or a chemical change. a. Touching a lit candle to hydrogen soap bubbles gives an explosion. b. Heating water in a flask produces moisture on the glass. c. Combining two colorless solutions gives a yellow solid. d. Pouring vinegar on baking soda produces gas bubbles. Solution: An observation that indicates a physical change is a change of physical state. The observations that suggest a chemical change include burning, fizzing, changing color, or forming an insoluble substance in solution. a. Hydrogen explodes; thus, it is a chemical change. b. Water is boiled; thus, it is a physical change. c. Two solutions give an insoluble substance; thus, it is a chemical change. d. Baking soda fizzes; thus, it is a chemical change.

55 Conservation of Mass Antoine Lavoisier found that the mass of reactants before a chemical change was always equal to the mass of products after a chemical change. This is the law of conservation of mass. Matter is neither created nor destroyed in a chemical reaction. Example: - If 1.0 gram of hydrogen combines with 8.0 grams of oxygen, 9.0 grams of water is produced. (1.0 g g = 9.0 g) - Consequently, 3.0 grams of hydrogen combine with 24.0 grams of oxygen to produce 27.0 grams of water. (3.0 g g = 27.0 g) - If 50.0 grams of water decompose to produce 45.0 grams of oxygen, how many grams of hydrogen are produced? 50.0 g water 45.0 g oxygen = 5.0 g hydrogen Dr. Coarfa - Chem1305

56 Potential and Kinetic Energy Potential energy, PE, is stored energy; it results from position or composition. Kinetic energy, KE, is the energy matter has as a result of its motion. - Energy can be converted between the two types. - A boulder at the top of the mountain has potential energy; if you push it down the mountain, the potential energy is converted to kinetic energy.

57 Learning Check Q1. An example of kinetic energy is A) a coiled spring. B) running water. C) a tree. D) natural gas. E) chemical energy. Q2. The energy associated with the motion of particles is called A) temperature. B) electrical energy. C) kinetic energy. D) chemical energy. E) potential energy. Q3. Which of the following is an example of potential energy? A) chewing food B) water stored in a reservoir C) burning wood D) a fan blade turning E) riding an exercise bike

58 Learning Check - Solution Q1. An example of kinetic energy is A) a coiled spring. B) running water. C) a tree. D) natural gas. E) chemical energy. Q2. The energy associated with the motion of particles in a substance is called A) temperature. B) electrical energy. C) kinetic energy. D) chemical energy. E) potential energy. Q3. Which of the following is an example of potential energy? A) chewing food B) water stored in a reservoir C) burning wood D) a fan blade turning E) riding an exercise bike Dr. Coarfa - Chem1305

59 KE, Temperature, and Physical State All substances have kinetic energy regardless of their physical state. Solids have the lowest kinetic energy, and gases have the greatest kinetic energy. As you increase the temperature of a substance, its kinetic energy increases.

60 Law of Conservation of Energy Just like matter, energy cannot be created or destroyed, but it can be converted from one form to another. This is the law of conservation of energy. There are six forms of energy: 1. Heat 2. Light 3. Chemical 4. Electrical 5. Mechanical 6. Nuclear Dr. Coarfa - Chem1305

61 Energy and Chemical Changes In a chemical change, energy is transformed from one form to another. For example: 61

62 Law of Conservation of Mass and Energy Mass and energy are related by Einstein s theory of relativity, E = mc 2. Mass and energy can be interchanged. The law of conservation of mass and energy states that the total mass and energy of the universe is constant.

63 Review Chapter 3 - Matter. Classification of Matter. Physical States of Matter, Physical Transformations. - Elements and their Symbols. Types of elements (metals, nonmetals, semimetals). States of matter of elements. - Periodic Table: groups (main/secondary) and periods; atomic number - Law of Definite Composition. Chemical Formula. - Physical and Chemical Properties. - Physical and Chemical Changes. - Law of Mass Conservation. - Potential and Kinetic Energy. Law of Energy Conservation. - Energy of Chemical Changes. Dr. Coarfa - Chem1305