Chemistry Unit Notes 8
Chemistry Unit Notes
Objective 4.01: Understand that naturally occurring and synthetic substances are chemicals
Key Terms 4.01
Chemical
Synthetic chemical
Matter
Element
Synthetic element
Mixture
Compound
Science book page numbers
· Ch 13 pgs 536-544
Notes 4.01
§ Chemical—substance that used in a chemical process or that is formed by a chemical process or it may also be any substance that is always made of the same thing
o Ex. Water is always H2O
§ Chemicals can be natural or synthetic
o Natural—CO2, H2O, gold, and sugar
o Synthetic—chemicals made in the laboratory
§ Ex. Plastic, steel, bronze
§ Matter is anything that has mass and volume
§ Mass is the amount of matter in a substance
§ Volume is the amount of space the substance occupies
§ The main three states of matter—solid, liquid, and gas
o Solid has a definite shape and volume—table, chair
o Liquid has a definite volume but not shape—water, oil
o Gas doesn’t have a definite volume or shape—air
§ Element-simplest form of matter, it can not be broken down into simpler substances by ordinary chemical means
o Changing an element to another element requires a lot of energy such as a nuclear explosion
o There are about 109 elements discovered
§ all of the known elements are combined into natural elements and synthetic elements—93 are natural elements, synthetic elements—16 that scientists created
§ Mixture—when two or more substances combine but do not join together chemically—the different parts keep their individual identities (properties)
o Ex. Cereal(mix of bran, fruit, milk, etc) and air (mix of gases)
§ Compound—when two or more elements combine chemically, individual substances join and do not keep their original properties
o Ex table salt (NaCl—sodium chloride), sodium by itself is a metal that explodes in water and chlorine is a poisonous gas—together you can eat it
§ Mixtures and compounds can be natural or synthetic
o Minerals are examples of natural mixtures
o Stainless steel is an example of synthetic mixture
http://1.bp.blogspot.com/_CxKx0boID9A/TUIo73lCUGI/AAAAAAAAAAM/RBJ3p3M6W4A/s1600/periodic_table3.gif
Discussion Question 1
Briefly explain the difference between a mixture and a compound and give two examples of each.
Objective 4.02: Evaluate evidence that elements combine in a multiple of ways to produce compounds that account for all living and nonliving substances
Key Terms 4.02
Compound
Molecule
Chemical formula
Atom
Proton
Neutron
Electron
Nucleus
Valence electrons
Ionic bond
Ion
Covalent bond
Science Book Reading
· Review Ch 13 Sec 1
· Read Ch 15 Sec 1 pgs 604-609
Notes 4.02
§ Compound—two or more substances chemically combine forming a new substance
o Have a definite composition---NaCl is always table salt
o Can be broken down into simpler substances by chemical means meaning NaCl can be broken into Na and Cl
o Can be identified by their physical properties meaning how you observe it and measure it
§ Molecule—smallest unit of a compound that has all the properties of the compound
o Ex smallest molecule of water would be H2O
§ Chemical formula—the makeup of a compound, uses chemical symbols and subscripts to identify the number of atoms of each element in a molecule of a compound
o Ex. H and O are chemical symbols of hydrogen and oxygen, 2 is the subscript for the number of hydrogen atoms needed to bond with oxygen to make water…this is the formula for water H2O
o When there is not a subscript for a symbol that means there is only 1 atom present, you need one sodium and one chlorine to make salt the chemical formula is NaCl
§ Atom—smallest unit of an element that has the properties of the element, also called the building block of an matter
http://0.tqn.com/d/chemistry/1/7/w/2/1/helium-atom.jpg
§ Three types of atom particles: protons, neutrons, and electrons
o Proton—a particle with a positive charge (+)
o Neutron—a particle without a charge (neutral) ( )
o Electron—a particle with a negative charge (-)
§ Protons and neutrons are found in the center of the atom called the nucleus
§ Electrons orbit the nucleus in a region called the electron cloud
· Electrons have different amounts of energy
· The closest electrons have less energy than electrons farther from the nucleus
· Electrons on the same energy level have similar amounts of energy
§ Each energy level can hold a certain number of electrons
Energy Level / Max Number of Electrons1 / 2
2 / 8
3 / 18
4 / 32
§ Valence electrons are found in the outer shell of the atom
o To determine how atoms combine to make compounds is dependent upon the number and arrangement of valence electrons
§ Chemical bonds—forces that hold atoms together
o Ionic bond-when a bond is formed by losing or gaining electrons
o Ion—atom that has gained or lost one or more electrons
§ Losses electrons—atom becomes positive
§ Gains electrons—atom becomes negative
§ Form because opposite charges attract
http://3.bp.blogspot.com/-0lmakBuwdIc/TVvctuCdf8I/AAAAAAAAADc/TKzKB8OzE5E/s1600/ionic.bond.jpg
§ To bond atoms need to have a total of eight electrons in their outer energy level
o Atoms with 1, 2, or 3 valence electrons normally give their electrons to atoms of elements that have 7, 6, or 5 valence electrons
§ Covalent bonds—atoms share valence electrons
o Form between elements whose atoms have 4, 5, 6, or 7 valence electrons
§ The same elements and be combined differently to form different elements
o Ex. H2O=water, H2O2=hydrogen peroxide; CO=carbon monoxide, CO2= carbon dioxide
§ Atomic Theory
o All matter is composed of atoms (building block)
o Atoms of a given element are identical—same number of protons and electrons
o Atoms of different elements combine in simple whole-number ratios to form chemical compounds—determined by valence electrons
o Compounds can make up living or nonliving substances
§ Living—proteins, carbohydrates, fats
§ Nonliving—plastics, rubber, medicines
Discussion Question 2
Is it possible to change a mixture into a compound?
Objective 4.03: Explain how the Periodic Table is a model for:
· Classifying elements
· Identifying the properties of elements
Key Terms 4.03
Atomic mass
Periodic table
Atomic number
Period
Group
Reactivity
Metalloid
Inert
Science Book Reading
· Review Ch 15 Sec 1
· Read Ch 15 Sec 2 pgs 610-617
Notes 4.03
§ Atomic mass—equal to the number of protons and neutrons in the nucleus
§ Mendeleev’s periodic table arranges elements according to the atomic mass
§ Elements with similar properties are found in the same column
§ Periodic table—chart that organizes information about all of the known elements according to their properties
http://www.click4chill.com/wp-content/uploads/2010/11/Periodic-Table-of-Elements-fix.jpg
§ Today elements are in order of the atomic number
§ Atomic number—number of protons in the nucleus of an atom
§ Period is the horizontal row in the periodic table
o Numbered 1-7, arranged in order of increasing atomic number
§ Chemical family or group is the Vertical column on the periodic table
o All have similar properties, numbered 1-18 and from 1A to 8A, all have same number of valence electrons
o Groups 1-2(IA-IIA) and 13-18(IIIA-VIIIA) are the main groups
o Groups 3-12 are called transition elements
o Elements on the left side of the periodic table are metals, except hydrogen
o Elements on the right side of the periodic table are nonmetals
Properties of Metal / Properties of NonmetalsSolid at room temperature, except mercury, which is a liquid / Most are gases, except bromine, which is a liquid
Malleable(shaped) and ductile (drawn into wire) / Brittle in solid phase
Have luster (shiny) / Normally dull
Have high thermal and electrical conductivity / Are poor conductors of heat and electricity
Tend to lose electrons in chemical reactions / Tend to gain electrons in chemical reactions
§ Reactivity describes how likely an element is to form bonds with other elements
§ Hydrogen is found above Group 1 but doesn’t belong to any group. It was placed here because it only has one valence electron. It’s properties are different from the other groups.
§ Group 1 (Alkali Metals) on periodic table
o Most chemically active
o One electron in the outer shell
o Easily combine with nonmetals
o Reactivity of the metal increases with increasing atomic number
§ Group 2 (Alkaline Earth Metal) on the periodic table
o Highly reactive but less reactive than group 1
o Reactivity of the metal increases with increasing atomic number
§ Group 3 –12 (transition metals) on the periodic table
o Generally hard solids with high melting points
o Often form colored ions
§ Metalloids
o Found along the zigzag between the metals and nonmetals on the periodic table
o Have properties of both metals and nonmetals
§ Group 17 (Halogens) on the periodic table
o Most reactive of the nonmetals
o Reactivity in nonmetals increases as atomic number decreases
o Fluorine (F) is the most reactive
o Halogens react with alkali metals to form salts
o Elements in this family are all states of matter
§ Fluorine(Fl) and Chlorine—gases
§ Bromine (Br)—liquid
§ Iodine (I) and Astatine (At) are solids at room temperature
§ Group 18 (Noble Gases) on periodic table
o Least reactive of all elements
o Inert—unable to react chemically
Discussion Question 3
When looking at different versions of the periodic table, why is hydrogen normally not attached to the periodic table?
Objective 4.04: Describe the suitability of materials for use in technological design:
· Electrical conductivity
· Density
· Magnetism
· Solubility
· Malleability
Key Terms 4.04
Property
Physical property
Chemical property
Metal
Nonmetal
Metalloid
Malleable
Ductile
Magnetism
Conductor
Insulator
Semiconductor
Density
Solubility
Science Book Readings
· Review Ch 15 Sec 2
· Read Ch 13 pgs 538-539
· Read Ch 13 Sec 2 pgs 546-550
· Read Ch 15 Sec 3 pgs 618-624
· Read Ch 15 Sec 4 pgs 625-635
Notes 4.04
§ Property—any factor that can be used identify and describe matter
o Helps for deciding the uses of various materials for technology
§ Physical property—observable and measureable characteristic without changing the identity of the substance
o Ex Mass, volume, color, hardness, and phase
o Every substance has its own unique properties
§ Chemical property—how the matter will change under certain conditions, this characteristic is unique to substances
o Ability to burn, rust, react to light, or react with acids are chemical properties of matter
§ Zigzag line divides the table into metalloids, metals, and nonmetals
§ Malleable—able to be hammered and shaped and rolled into thin sheets like foil
§ Ductile—able to be stretched or drawn into wires without breaking
§ Magnetism—attraction(moving towards) or repulsion (moving away) between like or unlike poles—iron, cobalt, and nickel are strong magnets
§ Conductor—a material or substance electricity or heat easily flows through
§ Insulators—a material that electricity or heat doesn’t easily flow through—rubber, wood, plastic, glass
§ Semiconductor—a material that has conductive properties that are variable—these can be useful for carrying electricity under certain conditions
§ Density—density=mass/volume certain substances have a specific density
§ Solubility—measure of how much of a substance can dissolve in a certain amount of another substance
o Carbon dioxide will dissolve more in water than oxygen, that’s why it is used in sodas
Discussion Question 4
Insulation is used in the walls of homes to regulate the flow of heat into and out of the house. Why would aluminum be a poor choice for insulation?
Objective 4.05: Identify substances based on characteristic physical properties:
· Density
· Boiling/Melting points
· Solubility
· Chemical reactivity
· Specific heat
Key Terms 4.05
Physical property
Density
Melting point
Boiling point
Specific heat
Solubility
Solution
Reactivity
Science Book Reading
Review pgs 538-539, 549, 550
Read Ch 16 Sec 2 pgs 698-703
Read Ch 14 Sec 1 & 2 pgs 572-583
Notes 4.05
§ Temperature is a physical property that is used to determine a substance because the temperature that a substance melts or boils is specific for the that substance
§ Melting point—the temperature at which a solid changes into a liquid—water 0°C
§ Boiling point—the temperature at which a liquid changes into a gas—water 100°C
§ Specific heat—the amount of heat needed to raise 1 gram (1 g) of a substance by 1 degree Celsius
o The unit of specific heat is joules per gram per degree Celsius (J/g · °C)
o Used to compare how different substances absorb heat
Substance / Specific Heat (J/g · °C)Water (liquid) / 4.18
Ethanol / 2.44
Water (solid) / 2.06
Aluminum / 0.897
Lead / 0.129
Of the above substances lead heats the fastest it has the lowest specific heat
§ Solubility, chemical properties, and reactivity are also identifiers of substances
Discussion Question 5
Is it possible for two different substances to have the same physical property? Explain.
Objective 4.06: Describe and measure quantities related to chemical/physical changes within a system:
· Temperature
· Volume
· Mass
· Precipitate
· Gas production
Key Terms 4.06
Physical change
Chemical change
Chemical reaction
Precipitate
Reactant
Product
Science Book Readings
Review pgs 538-539
Read pgs 552-554, 556, 650-655
Notes 4.06
§ Physical change-changing the physical properties of a substance without changing the substance—melting ice it is still water, tearing a sheet of paper it is still paper, and sharpening pencil it is still a pencil
§ Chemical change—changing a substance into a new substance this will make it have different properties—involve chemical reactions Sodium is a metal and chlorine is a gas when they react (chemically change) the new substance created is table salt
§ Chemical reaction—the process by which new substances are formed, most aren’t reversible
Sign of Chemical Reaction / ExplanationFormation of precipitate / A solid forms in a solution
Gas formation / If you see bubbles or visible gas
Color change / Substances change color
Energy change / A rise (exothermic) or fall(endothermic) in temperature, light is given off
§ Chemical bonds are either broken or formed—this requires energy—during a chemical reaction