Chapter 3 Matter and Energy by Christopher G. Hamaker Illinois State University © 2014 Pearson Education, Inc. 1

Matter Matter is any substance that has mass and occupies volume. Matter exists in one of three physical states: Solid Liquid Gas

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.

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.

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.

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. For example, Iron can be changed to a liquid at 1535o C and a gas at 2750o C. Chapter 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.

Liquid ↔ Gas Phase Changes When a liquid changes to a gas, the phase change is called vaporizing. A substance vaporizes as the temperature increases. When a gas changes to a liquid, the phase change is called condensing. 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: Mixtures 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: Heterogeneous mixtures Homogeneous mixtures Heterogeneous mixtures do not have uniform properties throughout. Sand and water is a heterogeneous mixture. Homogeneous mixtures have uniform properties throughout. Salt water is a homogeneous mixture.

Pure Substances There are two types of pure substances: Compounds 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 more than 95% of the mass of Earth’s crust, water, and atmosphere:

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. Curium is named for Marie Curie. Nobelium is named for Alfred Nobel.

Element Symbols Each element is abbreviated using a chemical symbol. The Swedish chemist J.J. Berzelius (1779-1848) proposed our current system of symbols in 1813. 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 Zinc– Zn

These symbols, abbreviations, enable us to write chemical reactions and complex compounds quickly and concisely. HCl + NaOH  NaCl + H2O REMEMBER: The first letter of a symbol is always capitalized but the second letter is never capitalized. Mg, Na, Br Most element symbols are comprised of two-letters. However we have many one-letter symbols. i.e. H, C, O, N

Critical Thinking: Aluminum or Aluminium? Most metals have names that end in –ium. However, element #13 is called aluminum in the USA and Canada, and aluminium in the rest of the world. The different spelling is believed to be from a spelling error which caught on in the USA and Canada. The official IUPAC name is “aluminium”; however, in 1993, IUPAC recognized the alternate spelling “aluminum.”

Types of Elements Elements can be divided into three classes: Metals Nonmetals 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

INTRODUCTION TO THE PERIODIC TABLE OF THE ELEMENTS The periodic table is a tabular arrangement of elements in rows and columns, which highlight the regular repetition of properties of the elements. It is a chemist’s best friend and for a student it is the biggest crib sheet in the room.

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.

Chemistry Connection: Elements 104 and Beyond Scientists continue to discover new, heavier elements beyond the current periodic table. Sometimes disagreements arise over naming of the new elements. IUPAC assigns names to new elements. Until IUPAC assigns a name, the elements are named using Latin prefixes for the numbers followed by the suffix –ium. Hence, element 104 is unnilquadium.

COMPOUNDS and CHEMICAL FORMULAS The French chemist Joseph Louis Proust (1754-1826) studied many compounds and found that the elements that made the compound were always contained in the same portions by mass. In 1799 from his studies he stated “Compounds always contain the same elements in a constant proportion by mass”. This is statement is now know as the Law of definite composition or the Law of constant proportion.

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. Chapter 4 © 2011 Pearson Education, Inc.

SOME ELEMENTS are found in nature as DIATOMIC MOLECULES SOME ELEMENTS are found in nature as DIATOMIC MOLECULES. There are seven (7) of them; H, N, O, F, Cl, Br, and I. As an element in a chemical equation they are always written as H2, N2, O2, F2, Cl2, Br2, and I2

Chemical Formulas A unit of matter composed of two or more nonmetal atoms is a molecule. A chemical formula is an expression of the number of atoms of each element in a compound. The chemical formula of sulfuric acid is H2SO4. NaCl, Al2O3, LiAlH4, CO2, NH4CO3

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 vitamin B3 has 6 carbon atoms, 6 hydrogen atoms, 2 nitrogen atoms, and 1 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 2 carbon atoms, 4 hydrogen atoms, and 2 OH units, for a total of 6 hydrogen atoms and 2 oxygen atoms. How many total atoms are in ethylene glycol? Ethylene glycol has a total of 10 atoms.

A MOLECULAR COMPOUND (substance) is composed of molecules. (NH4)2SO4 All molecular compounds must have a NET CHARGE OF ZERO.

PHYSICAL and CHEMICAL PROPERTIES No two substances have the same physical and chemical properties. In addition the physical and chemical properties of a compound are never the same as the properties of its constituent elements

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, heat and electrical conductivity, solubility, and physical state. A chemical property of a pure substance describes its chemical reactions with other substances.

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 sample does not change. These include changes in physical state or shape of a pure substance. A chemical change is a chemical reaction. The composition of the sample changes during a chemical change.

Evidence for Chemical Changes Gas release (bubbles) Light or release of heat energy A permanent color change

Chapter 4, Table 4.5

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.

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 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.

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.

Looking at the relationship between kinetic energy, temperature and physical states of matter we can see the relationships in the following manner.

In the solid state the force of attraction between particles holds the particles in fixed positions and allows little or no movement between the particles. When heated the temperature increases and the particles begin to vibrate in their fixed positions.

As the temperature increases the vibrations become greater and the force of attraction is overcome and the particles break free from each other and you now have a liquid state.

Liquid is a state of matter in which particles possess sufficient energy to overcome their mutual attraction and have limited movement within their container. Heating the liquid further gives the particles enough energy to completely overcome any force of attraction and the particles are free to fly about bump into the walls of their container or escape into the atmosphere. Study table 4.7 and figure 4.14

Chapter 4, Figure 4.14 Energy and Physical State

ENERGY and PHYSICAL CHANGES The law of conservation of energy applies to the change of physical states. Energy required changing a substance from a solid state to a liquid or a gas will be returned when the material returns to its original state.

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: Heat Light Chemical Electrical Mechanical Nuclear

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

ENERGY and CHEMICAL CHANGES The law of conservation of energy applied to chemical change is analogous to the change in physical states. The total energy before a reaction is the same as the total energy after the reaction even though some reactions require energy input while other reactions release energy.

Energy and Chemical Changes In a chemical change, energy is transformed from one form to another. For example: Chapter 4 © 2011 Pearson Education, Inc.

Critical Thinking: Lower Gasoline Bills In terms of expense, is it better to fill a gas tank in the cool morning, or in the warm afternoon? No matter the temperature, the number of gallons delivered is always the same. When the temperature is lower, a greater mass of gasoline is delivered for the same volume. However, the difference in mass between 40°F and 70°F is only about 1%.

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.

Chapter Summary Matter exists in three physical states: Solid Liquid Gas Substances can be converted between the three states. Substances can be mixtures or pure substances.

Chapter Summary, Continued Pure substances can be either compounds 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.