INTRODUCTORY CHEMISTRY INTRODUCTORY CHEMISTRY Concepts & Connections Sixth Edition by Charles H....
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Transcript of INTRODUCTORY CHEMISTRY INTRODUCTORY CHEMISTRY Concepts & Connections Sixth Edition by Charles H....
INTRODUCTORY CHEMISTRYINTRODUCTORY CHEMISTRYConcepts & Connections
Sixth Edition by Charles H. Corwin
Chapter 4 1© 2011 Pearson Education, Inc.
Chapter 4Matter and
Energyby Christopher Hamaker
2Chapter 4© 2011 Pearson Education, Inc.
Matter
• Matter is any substance that has mass and occupies volume.
• Matter exists in one of three physical states:
1. Solid
2. Liquid
3. Gas
3Chapter 4© 2011 Pearson Education, Inc.
Gaseous State
• In a gas, the particles of matter are far apart and uniformly distributed throughout the container.
• Gases have an indefinite shape and assume the shape of their container.
• Gases can be compressed and have an indefinite volume.
• Gases have the most energy of the three states of matter.
4Chapter 4© 2011 Pearson Education, Inc.
Liquid State
• In a liquid, the particles of matter are loosely packed and are free to move past one another.
• Liquids have an indefinite shape and assume the shape of their container.
• Liquids cannot be compressed and have a definite volume.
• Liquids have less energy than gases, but more energy than solids.
5Chapter 4© 2011 Pearson Education, Inc.
Solid State
• In a solid, the particles of matter are tightly packed together.
• Solids have a definite, fixed shape.
• Solids cannot be compressed and have a definite volume.
• Solids have the least energy of the three states of matter.
6Chapter 4© 2011 Pearson Education, Inc.
Physical States of Matter
7Chapter 4© 2011 Pearson Education, Inc.
Changes in Physical States
• Most substances can exist as either a solid, a liquid, or a 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.
8Chapter 4© 2011 Pearson Education, Inc.
Solid ↔ Liquid Phase Changes
• When a solid changes to a liquid, the phase change is called melting.
• A substance melts as the temperature increases.
• When a liquid changes to a solid, the phase change is called freezing.
• A substance freezes as the temperature decreases.
9Chapter 4© 2011 Pearson Education, Inc.
Liquid ↔ Gas Phase Changes
• When a liquid changes to a gas, the phase change is called vaporization.
• A substance vaporizes as the temperature increases.
• When a gas changes to a liquid, the phase change is called condensation.
• A substance condenses as the temperature decreases.
10Chapter 4© 2011 Pearson Education, Inc.
Solid ↔ Gas Phase Changes
• When a solid changes directly to a gas, the phase change is called sublimation.
• A substance sublimes as the temperature increases.
• When a gas changes directly to a solid, the phase change is called deposition.
• A substance undergoes deposition as the temperature decreases.
11Chapter 4© 2011 Pearson Education, Inc.
Summary of State Changes
12Chapter 4© 2011 Pearson Education, Inc.
Classifications of Matter
• Matter can be divided into two classes:
1. Mixtures
2. Pure substances
• Mixtures are composed of more than one substance and can be physically separated into its component substances.
• Pure substances are composed of only one substance and cannot be physically separated.
13Chapter 4© 2011 Pearson Education, Inc.
Mixtures
• There are two types of mixtures:
1. Homogeneous mixtures
2. Heterogeneous mixtures
• Homogeneous mixtures have uniform properties throughout.
– Salt water is a homogeneous mixture.
• Heterogeneous mixtures do not have uniform properties throughout.
– Sand and water is a heterogeneous mixture.
14Chapter 4© 2011 Pearson Education, Inc.
Pure Substances
• There are two types of pure substances:
1. Compounds
2. Elements
• Compounds can be chemically separated into individual elements.
– Water is a compound that can be separated into hydrogen and oxygen.
• An element cannot be broken down further by chemical reactions.
15Chapter 4© 2011 Pearson Education, Inc.
Matter Summary
16Chapter 4© 2011 Pearson Education, Inc.
Occurrence of the Elements
• There are over 100 elements that occur in nature; 81 of those elements are stable.
• Only 10 elements account for 95% of the mass of Earth’s crust:
17Chapter 4© 2011 Pearson Education, Inc.
Elements in the Human Body
• Oxygen is the most common element in Earth’s crust and in the human body.
• While silicon is the second most abundant element in Earth’s crust, carbon is the second most abundant in the body.
18Chapter 4© 2011 Pearson Education, Inc.
Names of the Elements
• Each element has a unique name.
• Names have several origins:
– Hydrogen is derived from Greek.
– Carbon is derived from Latin.
– Scandium is named for Scandinavia.
– Nobelium is named for Alfred Nobel.
– Yttrium is named for the town of Ytterby, Sweden.
19Chapter 4© 2011 Pearson Education, Inc.
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.
20Chapter 4© 2011 Pearson Education, Inc.
Other Element Symbols
• For some elements, the chemical symbol is derived from the original Latin name.
Gold – Au Sodium – Na
Silver – Ag Antimony – Sb
Copper – Cu Tin – Sn
Mercury – Hg Iron – Fe
Potassium – K Tungsten – W
21Chapter 4© 2011 Pearson Education, Inc.
Types of Elements
• Elements can be divided into three classes:
1. Metals
2. Nonmetals
3. Semimetals or metalloids
• Semimetals have properties midway between those of metals and nonmetals.
22Chapter 4© 2011 Pearson Education, Inc.
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.
23Chapter 4© 2011 Pearson Education, Inc.
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.
• Eleven nonmetals occur naturally in the gaseous state.
24Chapter 4© 2011 Pearson Education, Inc.
Summary of Properties
25Chapter 4© 2011 Pearson Education, Inc.
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.
26Chapter 4© 2011 Pearson Education, Inc.
The Periodic Table
27Chapter 4© 2011 Pearson Education, Inc.
Metals, Nonmetals, and Semimetals
• Metals are on the left side of the periodic table, nonmetals are on the right side, and the semimetals are in between.
28Chapter 4© 2011 Pearson Education, Inc.
Physical States of the Elements
• Shown are the physical states of the elements at 25 °C on the periodic table.
29Chapter 4© 2011 Pearson Education, Inc.
Law of Definite Composition
• The law of definite composition states that “Compounds always contain the same elements in a constant proportion by mass.”
• Water is always 11.19% hydrogen and 88.81% oxygen by mass, no matter what its source.
• Ethanol is always 13.13% hydrogen, 52.14% carbon, and 34.73% oxygen by mass.
30Chapter 4© 2011 Pearson Education, Inc.
Chemical Formulas
• A particle composed of two or more nonmetal atoms is a molecule.
• A chemical formula is an expression of the number of and types of atoms in a molecule.
• The chemical formula of sulfuric acid is H2SO4.
31Chapter 4© 2011 Pearson Education, Inc.
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 six carbon atoms, six hydrogen atoms, two nitrogen atoms, and one oxygen atom. What is the chemical formula?
C6H6N2O
32Chapter 4© 2011 Pearson Education, Inc.
Interpreting Chemical Formulas
• Some chemical formulas use parentheses to clarify atomic composition.
• Ethylene glycol, a component of some antifreezes, has a chemical formula of C2H4(OH)2. It contains two carbon atoms, four hydrogen atoms, and two OH units, giving a total of six hydrogen atoms and two oxygen atoms. How many total atoms are in ethylene glycol?
• Ethylene glycol has a total of ten atoms.
33Chapter 4© 2011 Pearson Education, Inc.
Physical and Chemical Properties
• A physical property is a characteristic of a pure substance that we can observe without changing its composition.
• Physical properties include appearance, melting and boiling points, density, conductivity, and physical state.
• A chemical property describes the chemical reactions of a pure substance.
34Chapter 4© 2011 Pearson Education, Inc.
Chemical Properties
Sodium metal (Na)
reacts with
chlorine gas (Cl2)
to produce
sodium chloride (NaCl).
35Chapter 4© 2011 Pearson Education, Inc.
Physical and Chemical Change
• A physical change is a change where the chemical composition of the substance is not changed.
• These include changes in physical state or shape of a pure substance.
• A chemical change is a chemical reaction.
• The composition of the substances changes during a chemical change.
36Chapter 4© 2011 Pearson Education, Inc.
Evidence for Chemical Changes
• Gas release (bubbles)
• Light or release of heat energy
• Formation of a precipitate
• A permanent color change
37Chapter 4© 2011 Pearson Education, Inc.
Conservation of Mass
• Antoine Lavoisier found that the mass of substances before a chemical change was always equal to the mass of substances after a chemical change.
• This is the law of conservation of mass.
• Matter is neither created nor destroyed in physical or chemical processes.
38Chapter 4© 2011 Pearson Education, Inc.
Conservation of Mass Example
• If 1.0 gram of hydrogen combines with 8.0 grams of oxygen, 9.0 grams of water is produced.
• Consequently, 3.0 grams of hydrogen combine with 24.0 grams of oxygen to produce 27.0 grams of water.
• 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
39Chapter 4© 2011 Pearson Education, Inc.
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 motion.
• Energy can be converted between the two types.
• A boulder at the top of the hill has potential energy; if you push it down the hill, the potential energy is converted to kinetic energy.
40Chapter 4© 2011 Pearson Education, Inc.
Energy
41Chapter 4© 2011 Pearson Education, Inc.
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.
42Chapter 4© 2011 Pearson Education, Inc.
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. Electrical
4. Mechanical
5. Chemical
6. Nuclear
43Chapter 4© 2011 Pearson Education, Inc.
Energy and Chemical Changes
• In a chemical change, energy is transformed from one form to another. For example:
44Chapter 4© 2011 Pearson Education, Inc.
Law of Conservation of Mass and Energy
• Mass and energy are related by Einstein’s theory of relativity, E = mc2.
• 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.
45Chapter 4© 2011 Pearson Education, Inc.
Chemistry Connection: Al Recycling
• Although aluminum is very abundant in Earth’s crust, it is difficult to purify it from its ore.
• The energy from 8 tons of coal is required to produce 1 ton of aluminum metal from its ore.
• However, it only takes the energy from 0.4 tons of coal to produce 1 ton of aluminum from recycled scrap.
46Chapter 4© 2011 Pearson Education, Inc.
Chapter Summary
• Matter exists in three physical states:
1. Solid
2. Liquid
3. Gas
• Substances can be converted between the three states.
• Substances can be mixtures or pure substances.
47Chapter 4© 2011 Pearson Education, Inc.
Chapter Summary, Continued
• Pure substances can be either compound or elements.
• The elements are arranged in the periodic table.
• Each element has a name and a one- or two-letter symbol.
• Elements are classified as either metals, nonmetals, or semimetals.
48Chapter 4© 2011 Pearson Education, Inc.
Chapter Summary, Continued
• A physical change is a change in physical state or shape.
• A chemical change is a change in the chemical composition of a substance.
• Both mass and energy are conserved in chemical and physical changes.