Chemistry is the study of

• The structure and composition of matter

• The changes that occur in this composition of matter

• The mechanisms that bring about these changes

Different Kinds of Chemistry

• Biochemistry: living things

• Organic chemistry: carbon containing compounds

• Inorganic chemistry: non carbon containing compounds (metals)

• Physical chemistry: chemistry and energy

• Analytical chemistry: the chemistry of unknowns (forensic chemistry)

• Nuclear chemistry: chemistry of the nucleus

Matter: anything that has mass and occupies space

States of Matter

• Solid: has a definite volume, definite shape

• Liquid: has a definite volume, no definite shape

• Gas: has neither a definite volume or definite shape

• Plasma: high temperature and energy state wherein most atoms now have charges

Theory: an explanation of how/why something occurs based on a wide body of evidence which is not yet disproven

Law: an observation that tells you what happens, but not the why, and is also not yet disproven

The Kinetic Theory of Matter

• The particles of matter are always in motion and this motion has consequences

• Used to determine the states of matter

Properties of Matter

• Inertia: resistance to change in state of motion

• Mass: measure of the quantity of matter = measure with a balance

• Weight: measure of Earth’s gravitational attraction = measure with a scale

Types of Properties

• Extensive: depends on the amount of matter that is present = dependent on amount

  • Ex: Mass

• Intensive: does not depend on the amount of matter that is present = independent on amount

  • Ex: Density

• Physical Property: characteristic that can be observed or measured without changing the identity of substance

• Chemical Property: characteristic that relates to a substance’s ability to undergo changes that transform it into different substances

Physical Change

• Reversible process

• Identifying properties of the substance remain unchanged

• No atoms or molecules are destroyed, but the spacing between them changes

Chemical Change

• Can be a reversible or irreversible processes

• Different substances with new properties are formed

• Atoms and moleules are rearranged

Nuclear Change

• Most are irreversible change

• Different substances with new properties are formed

• Atoms are destroyed and new ones are made

5 Signs of a Chemical Reaction

• Production of light

• Color Change

• Production of a gas

• Precipitate is formed - insoluble solid

• Production of heat

Reaction = Undergo a Chemical Change

• Reactants → Products

• In → Out

• Before → After

Energy of reactions

• Exothermic: process that gives off energy

• Endothermic: process that absorbs energy

Chemical: any substance that has a definite composition (synonym - substance)

3 Other Classes of Matter

• Mixtures: a material consisting of 2 or more kinds of matter, each retaining its own characteristic properties

  • Heterogeneous

    • Different from point to point

    • Matter that has parts with different properties

  • Homogeneous

    • Same from point to point

    • Matter that has similar properties throughout

• Pure Substances

  • Elements

    • A substance that cannot be further decomposed

  • Compounds

    • A substance that may be decomposed into 2 or more simpler substances

Mixture vs. Compound

• Mixture

  • Components may be present in any proportion

  • Components do not lose their “identity”

  • Components can be separated by physical means

  • In preparation there is no evidence of a chemical reaction taking place

• Compounds and Elements

  • Components always have a definite proportion (can’t change the ingredient amounts)

  • Components lose their identity

  • Components can be separated by chemical means

  • In preparation evidence of a chemical reaction is usually apparent

  • Has a chemical a formula NaCl, H20, C12H22O11

Element Symbols

• 1st letter = always capitalized, usually 1st letter of name

• 2nd letter = never capitalized

• All element symbols come from the Latin version of the element name

The States of Elements at Room Temperature

• Color of symbol tells state

• Black = solid

• Blue = liquid

• Red = gas

• Outline = manmade

The Nucleus

• Comprised of the 2 nucleons

  • Protons

  • Neutrons

Isotopes

• Not all atoms of the same element have the same mass due to different numbers of neutrons in those atoms

Radioactivity

• Some nuclides of an element may be unstable, or radioactive

  • Referred to as radioisotopes

Types of Radioactive Decay

• 2 Main Types

  • Nuclear Fission

    • Splitting apart of nuclei

    • Results in two smaller atoms

    • Does not normally occur in nature

    • Takes little energy to split -- releases energy 1,000,000 times greater than a chemical reaction (lower than nuclear fusion)

    • Ex: Atomic Bomb

  • Nuclear Fusion

    • Joining together of nuclei

    • Results in larger atoms

    • Often needs a “trigger” to start process -- requires a lot of energy and high temperature

    • Energy released 3-4 times larger than fission (so about 4,000,000 times that of a chemical reaction)

    • Ex: the Sun, Hydrogen bombs

• Alpha Decay: The loss of an a-particle (a helium nucleus)

• Beta Decay: The loss of a B-particle (a high energy or fast moving electron)

• Positron Emission

  • Some nuclei decay by emitting a positron, a particle that has the same mass as but an opposite charge to that of an electron

• Gamma Emission

  • Loss of a y-ray, which is high-energy radiation that almost always accompanies the loss of a nuclear particle

  • Gamma rays are not charged particles like a and B particles

  • Gamma rays are electromagnetic radiation with high frequency

  • When atoms decay by emitting a or B particles to form a new atom, the nuclei of the new atom formed may still have too much energy to be completely stable

    • This excess energy is emitted as gamma rays

• Electron Capture

  • Addition of an electron to a proton in the nucleus

    • The result of this process is that a proton is transformed into a neutron

Neutron-Proton Ratios

• Any element with more than one proton (i.e., anything but hydrogen) will have repulsions between the protons in the nucleus

• A strong nuclear force helps keep the nucleus from flying apart

• Neutrons play a key role in stabilizing the nucleus (more neutrons = more strong force)

• Therefore, the ratio of neutrons to protons is an important factor

• For smaller nuclei (#protons <= 20) stable nuclei have a neutron-to-proton ratio close to 1:1

• As nuclei get larger, it takes a greater number of neutrons to stabilize the nucleus

Stable Nuclei

• There are no stable nuclei with an atomic number greater than 83

• Nuclei with such large atomic numbers tend to decay by alpha emission

Half-Life

• The time it takes for half of your isotope to decay into another element

Electrons in Atoms

• Electrons can only orbit the nucleus in specific, allowed pathways

• They move toward and away from the nucleus by “steps” or discrete amounts of energy that are released or absorbed

• Electrons farther from the nucleus have more energy. Those closer to the nucleus have less energy

• Ground State: lowest energy state

  • This means that electrons are found in shells closer to the nucleus

• Excited State: higher potential energy of an atom

  • A form of heat, light, electrical or mechanical energy is needed to go from the ground to an excited state

  • As electrons increase in energy, they move away from the nucleus and into outer shells

Absorption: moves electrons from a ground state to a higher energy state

Emission: lets electrons fall back down to a lower energy state

• Usually light

The kind of light emitted by each element is unique because each element has a unique arrangement of electrons

Carbon footprint is the summation of all emissions, as a result of activities

• Ex: the fuel burned by cars or buses to get to school

• Chemicals in carbon, such as carbon dioxide, are harmful

• Should be taken seriously because of its effect on the temperature.

Energy comes from the sun

• Solar power/sunlight can be converted into electricity

• The Sun influences all forms of energy like coal and other renewable sources

• The Sun also influences things like heat, wind, and plants

Elements in the Sun

• Predominant one is Hydrogen

• Small amount of Helium is present, with traces of other elements

Life cycle of a star

• Formation of stars occurs as a result of gravitational centers with nebulas that draw minerals together

• Hydrogen in stars (the fuel) can run out, and they collapse → explosion by increasing temperature and presure, counteracting gravity

• Larger stars have shorter lifespans because of their mass

Death of stars

• Different deaths can occur due to their shape and size

• Occurs due to the exhaustion of reactants/fission energy

• Normal stars become white dwarfs

• Large stars turn into black holes or nebulas

Particles found in the center of the atom: Protons and neutrons

Neutral atoms have the same number of protons and electrons

Positive ions have more protons than electrons

Negative ions have less protons than electrons

The ratio of protons to electrons is based on the charge of the atom

The rule for determining the mass number of an atom or ion is protons and neutrons that are present in the nucleus

Element symbol is determined by the number of protons

• The letters representing the chemical element

Charge is determined by the protons and electrons

• The value difference between protons and electrons

Atomic number is determined by the number of protons

Mass number is determined by the protons and netrons

Isotopes

• Protons and neutrons affect the stability of the atom

• Electrons do not affect the stability of the atom

• Requirements for 2 atoms to be isotopoes of each other

  • They have to have the same number of protons but a different number of neutrons

  • They need to have the same charge

Similarities/Differences between an atom, ion, and isotope

• They have the same number of protons

• Isotopes have a different amount of neutrons

• Ions have a different amount of electrons

Order of the Periodic Table

• Column (verticle) = Group or Family

  • Alkali Metals

  • Alkaline Earth Metals

  • Transition Metals

  • Boron Family

  • Carbon Family

  • Nictides (Nitrogen Family)

  • Chalcogens (Oxygen Family)

  • Halogens

  • Noble Gases

• Row (horizontal) = Period or Series

  • Actinide

  • Lanthanide

• Metals/Mettaloids/Nonmetals

  • Left

  • Zigzag

  • Right