Chapter 3 Matter and Energy

Matter Matter is any substance that has mass and occupies volume. Matter exists in one of three physical states: Solid (s) Liquid (l) Gas (g) Chapter 4

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. They can be compressed into a liquid, like liquid Nitrogen, N2(l) or a solid, like dry ice, CO2(s). Gases have the most energy of the three states of matter. Chapter 4

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. Chapter 4

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. Chapter 4

Physical States of Matter Chapter 4

Changes in Physical State 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. Chapter 4

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. Chapter 4

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. Chapter 4

Solid ↔ Gas Phase Changes When a solid changes directly to a gas, the phase change is called sublimation. Example: Moth ball. 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. Chapter 4

Summary of State Changes Chapter 4

Classifications of Matter Matter can be divided into two classes: Mixtures (also called solutions) 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. Chapter 4

Mixtures There are two types of mixtures: homogeneous mixtures heterogeneous mixtures Homogeneous mixtures have uniform properties throughout. Beer; salt and water. Air. Alloy. Heterogeneous mixtures do not have uniform properties throughout. Sand and water. Sulfur and sand. Oil and water. Chapter 4

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. Chapter 4

Matter Summary Chapter 4

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 the Earth’s crust: Chapter 4

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. Chapter 4

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 Chapter 4

Element Symbols Each element is abbreviated using a chemical symbol. The symbols are 1 or 2 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. Chapter 4

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 Chapter 4

Types of Elements Elements can be divided into three classes: Metals: Na, Mg, Al, Cr, Hg,…. etc. Note: All metals are soild except Hg which is a liquid. Nonmetals: H, C, P, Cl, Ar,….etc. All nonmetals are either solid or gas except Br2 which is a liquid. semimetals or metalloids: B, Si, Ge,….etc. Semimetals have properties midway between those of metals and nonmetals. Chapter 4

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. Chapter 4

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. They are H2, N2, O2, F2, Cl2, He, Ne, Ar, Kr, Xe, Rn. Chapter 4

Summary of Properties Chapter 4

Periodic Table of the Elements Each element is assigned a number to identify it. It is called the atomic number. It’s also called the proton number. Hydrogen is 1; helium is 2; up to uranium, which is 92. The elements are arranged by atomic number on the periodic table. Chapter 4

The Periodic Table Chapter 4

Metals, Nonmetals, & Semimetals Metals are on the left side of the periodic table, nonmetals are on the right side, and the semimetals are in between. Chapter 4

Physical States of the Elements Shown are the physical states of the elements at 25 °C on the periodic table. Chapter 4

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

Chemical Formulas A 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 H2SO4. Chapter 4

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? C6H6N2O Chapter 4

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. There are 2 carbon atoms, 4 hydrogen atoms, and 2 OH units, giving 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. Chapter 4

Physical & 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. Chapter 4

Physical & 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. Simply put, you’ll always be able to get it back when a substance undergoes physical changes by adjusting temperature, pressure, etc. Example: Sublimation, melting, boiling, etc. A chemical change is a chemical reaction. The composition of the substances changes during a chemical change. Simply put, you cannot get it back when a substance undergoes a chemical reaction. Example: Boiling an egg, fruits ripe, nail rust, combustion (or burning or explosion), decomposition, combination, oxidation-reduction, baking a potato, color of carpet faded by sunlight, magnesium metal dissolves in vinegar to produce hydrogen gas, etc. In nutrition, it’s metabolism or digestion. Chapter 4

Evidence for Chemical Changes gas release (bubbles) light or release of heat energy formation of a precipitate a permanent color change Chapter 4

Conservation of Mass 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. Chapter 4

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 Chapter 4

Potential & 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. Chapter 4

KE, Temperature, and Physical State All substances have kinetic energy no matter what physical state they are in. 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. Chapter 4

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, electrical, mechanical, chemical, and nuclear. Chapter 4

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

Law of Conservation of Mass & 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 4

Chemistry Connection: Al Recycling Although aluminum is very abundant in the 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 4

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 4

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 1- or 2-letter symbol. Elements are classified as either metals, nonmetals, or semimetals. Chapter 4

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. Chapter 4