Chemistry Midterm 2022-2023

Study guide with review questions and vocabularyfrom Chapters 1-7

Scientific Method

The process of observing, asking questions, and seeking answers through tests and experiments

Matter

Anything that has mass and takes us space

Phases of Matter

Solid, Liquid, and Gas

Mixtures

Substances can be physically mixed together to make

Element

Atoms of the same type

Compounds

When atoms of different elements chemically combine together

Chemical change

Chemical change = a change which results in a change in the chemical substance, usually not reversible

Physical change

Physical change = a change in which the chemical substance does not change, usually reversible

Measurements

quantitative observation

Uncertainty

denotes the precision of the measurement

Units

provide context and scale

Metric System

used in most of the world, uses prefixes to create larger or smaller units

Accuracy

a measure of the correctness of a value, or how close it is to the true or accepted value

Precision

 a measure of the exactness of a value, or how close the values are to each other

Accuracy vs precision

Accuracy refers to how close a measurement is to the true or accepted value. Precision refers to how close measurements of the same item are to each other.

Periodic table

Is a rows and columns arrangement of the chemical elements

Atomic number

number of protons + number of neutrons

Average atomic mass

the mass of an atom

Groups

the vertical columns of the periodic table; elements in the same group have similar chemical properties and behaviors

Periods

the horizontal rows on the periodic table; indicates the energy level, and the approximate size of the atom

Phases

Black: solid, Blue: Liquid, Red: Gas

Metals

found on the left and middle of the Periodic table

Nonmetals

found on the upper right of the Periodic table

Protons

the identity of the atom

Electrons

the mass of the  atom (w/ protons)

Neutrons

the charge of the atom (w/ protons)

Isotopes

atoms of the same element that have different masses (same number of protons, different number of neutrons)

Dalton atomic theory

All elements are composed of atoms, All atoms of a given element are identical, Atoms of different elements are different, Compounds consist of the atoms of different elements, Atoms are neither created nor destroyed in a chemical reaction

Thomson atomic theory

showed that atoms consisted of smaller particles, now known as electrons (cathode ray tube and plum pudding model)

Rutherford atomic theory

discovered that the atom has a small, dense, positively charged nucleus (gold foil experiment)

Bohr atomic theory

the electrons orbit the nucleus at specific energies, and can jump between the orbits, by absorbing or emitting energy (Planetary model)

Schrodinger atomic theory

proposed that electrons behave according to mathematical wave functions

Atomic orbitals

clouds of electron density, based on mathematical probabilities

Quantum numbers

Principle energy level, Subshell or sublevel, Spin

Electron configurations

states which atomic orbitals are filled and the number of electrons in the orbitals

Valence electrons

electrons in the outermost shell (energy level) of the atom

Electronegativity

a measure of how strongly an atom holds onto/pulls on shared electrons

Ionization energy

the amount of energy required to remove an electron from an atom

Ion

an atom (or a group of atoms) with an electrical charge

Properties of metals

Low electronegativity, Low ionization energy, Tend to lose electrons

Properties of nonmetals

High electronegativity, High ionization energy, Tend to gain electrons

Cation

an ion with a positive charge

Anion

an ion with a negative charge

Polyatomic ions

2 or more atoms bonded together that have charge

Ionic bond

electrons are transferred from one atom to the other, no sharing of electrons

Properties of Ionic compounds

Ionic bonds are generally very strong, Most ionic compounds are solids at room temperature with high melting points, They conduct electricity when dissolved in water or in the liquid phase, Form a crystal lattice structure

Ionic compound

chemical compound composed of ions held together by electrostatic forces

Covalent bonding

pairs of electrons shared between 2 atoms

Molecule

2 or more atoms covalently bonded together

Polar bond

unequal sharing of electrons

Nonpolar bond

equal sharing of electrons

Lewis Structures

2-dimensional representations of covalent molecules

Lone Pairs

represented by dots around the atoms

Molecular geometry

the 3-dimensional shape of molecules

Central atom

an atom bonded to 2 or more other atoms

Terminal atom

an atom bonded to only 1 other atom

Polarity of molecules

separation of charge, or an uneven distribution of electrons in a molecule

Scientific notation

used to express very large or very small numbers

Significant figures

the number of digits in a measurement that carry meaning

Equivalent statement

Example: 1 inch = 2.54 centimeters

Conversion factor

\

Density

ratio of the mass to the volume

Percent error

Indicates how far from the true or accepted value a measurement is

Moles

a unit to measure the number of atoms (or molecules) in a sample

Counting by weighing

a process to determine the number of things without physically counting them, by measuring their mass

Average atomic mass

the mass of the average atom of an element

Amu

1 amu = 1.66 x 10-24 grams

Molar mass

the mass in grams of 1 mole of an element or compound

Percent composition

the percent by mass of each element in a compound

Empirical formula

the smallest integer ratio of the elements in a compound

Molecular formula

the actual number of atoms of each element in the compound

Law of Mass conversation

Matter cannot be created or destroyed during a chemical reaction, it can only change forms

Chemical equations

Represent what is occurring during a chemical reaction

Reactant

Chemicals at the start of the reaction, and are written to the left of the arrow

Product

Chemicals produced at the end of the reaction, and are written to the right of the arrow

Coefficient

Integer numbers written to the left of each substance, indicates how many of each substance is involved in the reaction

Precipitation

2 aqueous ionic compounds react to form a solid ionic compound (and another compound, usually aqueous)

Acid-Base

an acid (containing hydrogen) and a base (containing hydroxide) react to form water (and another compound)

Synthesis

making a compound from its elements

Decomposition

breaking down a compound into its elements

Combustion

something combines with oxygen, usually produces heat/light

Single Displacement

one element takes the place of another element in a compound

Chemistry

the study of matter, it’s interactions, and changes

What are the 3 things a measurement must contain?

1. The number 
2. The unit - provides context and scale
3. A degree of uncertainty - denotes the precision of the measurement

Diatomic elements

elements that exist in their natural state as molecules consisting of 2 atoms chemically bonded

Light

Electromagnetic radiation, a form of energy

Ground state

the lowest energy state possible for an atom or molecule

Excited State

Excess energy

Aufbau Principle

electrons fill the orbitals in order from lowest energy to highest energy; ‘electrons are lazy’

Hund’s Rule

each orbital in a sublevel is filled with 1 electron before any are filled with a second; ‘electrons are anti-social’

Pauli Exclusion Principle

no 2 electrons can have the same 4 quantum numbers; an orbital can only hold 2 electrons, and they must have opposite spins 

The state of matter characterized by both a definite shape and a definite volume is a

solid

Burning wood is an example of a

chemical change

When a substance changes and still retains its original chemical identity, the change is called

Physical

The state of matter in which the atoms or molecules are far apart and have very little interaction with each other is

gas

Which metric unit would be used to measure the mass of an object

Kilograms

When several substances are placed together but do not combine chemically they form a

mixture

What does the prefix kilo- indicate?

10^3

What scientist proposed the existence of distinct energy levels after observing the consistent color produced when energizing samples of hydrogen gas?

Bohr

Who proposed an atomic model based on the idea that electrons behave as waves, rather than particles?

Schrodinger and de Broglie