Chapter 4 1

Chapter 3 Matter and Energy

Chapter 4 2

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 3

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 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 5

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 6

Physical States of Matter

Chapter 4 7

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 8

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 9

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 10

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 11

Summary of State Changes

Chapter 4 12

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 13

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 14

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 15

Matter Summary

Chapter 4 16

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 17

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 18

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 19

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 20

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 21

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 22

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 23

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 24

Summary of Properties

Chapter 4 25

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 26

The Periodic Table

Chapter 4 27

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 28

Physical States of the Elements

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

Chapter 4 29

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 30

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 31

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 32

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 33

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 34

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 35

Evidence for Chemical Changes

• gas release (bubbles)

• light or release of heat energy

• formation of a precipitate

• a permanent color change

Chapter 4 36

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 37

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 38

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 39

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 40

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 41

Energy and Chemical Changes

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

Chapter 4 42

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 43

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 44

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 45

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 46

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.