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


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.


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.


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.


Physical States of Matter


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.


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.


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.


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.


Summary of State Changes


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.


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.


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.


Matter Summary


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:


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.


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.


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.


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


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.


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.

• Eleven nonmetals occur naturally in the gaseous state.


Summary of Properties


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.


The Periodic Table


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.


Physical States of the Elements

• Shown are the physical states of the elements at 25 °C on the periodic table.


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.


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.


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


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.


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.


Chemical Properties

Sodium metal (Na)

reacts with

chlorine gas (Cl2)

to produce

sodium chloride (NaCl).


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.


Evidence for Chemical Changes

• Gas release (bubbles)

• Light or release of heat energy

• Formation of a precipitate

• A permanent color change


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.


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


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.


Energy


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.


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


Energy and Chemical Changes

• In a chemical change, energy is transformed from one form to another. For example:


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.


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.


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.


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.


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.

INTRODUCTORY CHEMISTRY INTRODUCTORY CHEMISTRY Concepts & Connections Sixth Edition by Charles H....

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