chemistry final
Chemistry- is the study of the composition, structure, properties, and reactions of matter. Matter is another word for all the substances that make up our world.
A chemical- is a substance that always has the same composition and properties wherever it is found.
The scientific method- is a process that scientists use to make observations in nature, gather data, and explain natural phenomena.
Measurements- Describe the attributes of matter. (anything that has mass)
Characteristics-
volume
length or distance
time
temperature
Base units- can be combined to make derived units
density = mass (g)/volume (ml)
Significant figures are all the meaningful digits in a measurement plus one estimated digit at the end.
Significant figures- all digits that are not zero are always significant figures
zeros that are located between sigfig are significant
zeros that appear before sigfigs are called leading zeros and are not significant.
zeros that appear after sigfig digits in a number with no decimal are not significant
zeros that appear after sigfig digits in the presence of a decimal are significant
The final answer in a calculation must have the same number of significant digits as the measurement with the fewest significant figures
Conversion factors- are ratios of two units whose purpose is to change from one unit to another.
Measurement numbers - required by instrument tools or devices.
Pure substance- anything with a definite composition
mixture- a combination or 2 or more pure substances
homogeneous- a uniform composition or even distribution, aka solution
Heterogeneous- not uniform, the different components are easily identified
compounds- a combination of 2 or more elements
Separation of a mixture
Filtration- separates a mixture physically by pouring or decanting the mixture through a filter paper
Chromatography - the chemical method used to separate components of a liquid mixture.
Mixture can exist in three states of matter
solid- definite shape and volume
liquids- definite volume and indefinite shape
gases- indefinite volume and indefinite shape
Physical property- characteristics that are observed or measured without affecting the identity of a substance
Melting- solids into liquids
freezing- liquid into solid
evaporation/vaporization- liquid to gases
condensation- gases to liquid
sublimation- solid to gas without liquid state
deposition- gas to solid
Chemical properties- the ability of a substance to change into a new substance
ex. iron into rust
Heat of fusion- the energy needed to melt ice or freeze water
Chemical symbols- identify the elements they appear as a single or capital letter or 2 letter combination
Atom- the simplest form of matter
made up of three particles
nucleus- protons, neutrons
electrons
Mass number- describes the number of particles in the nucleus
atomic number- number of protons only
- Protons identify elements
Periodic table-
arranged in increasing atomic number
1st table made by Dimitri Mandelave
arrangement of table
vertical colums reflected as groups or families with group number written on top
Horizontal rows are called periods
Groups have specific names
group a- alkali metals
group 2a- alkaline earth metals
group 6a- calcogens (oxygen, sulfer)
group 7a- halogens (clorine, iodine)
group 8a Noble gases
metalloids located on left side of table
non-metals on right side
small group called metaloids aka semi-metals (middle of table)
atomic size increases going down the group
Further from the nucleus, the + and - charges are less attracted to each other
metals- will lose electrons to form ions
Ionization energy- The energy needed to remove an electron from the outermost energy level of an atom.
Isotope: An atom that differs only in mass number from another atom of the same element. Isotopes have the same atomic number (number of protons), but different numbers of neutrons.
Metal and non-metal forms an ionic bond
metals name 1st and non metal changes to “ide”
ex. sodium and fluorine
sodium fluoride
Lewis dot structure- symbols of the elements surrounded to represent the valence electrons
Ionic compound
1. Lithium + Chlorine
Step 1: Write the ions
Lithium (Li) is in Group 1 → forms Li⁺
Chlorine (Cl) is in Group 17 → forms Cl⁻
Step 2: Combine ions in a neutral ratio
Li⁺ + Cl⁻ → LiCl
Ionic compound: Lithium chloride
Formation equation:
2Li (s) + Cl₂ (g) → 2LiCl (s)
Polyatomic Ions
“ate” more oxygen
ex. MgSO4- magnesium sulfate
“ite” less oxygen
NO2 - sulfite
MgSO₄
Explanation:
Magnesium (Mg) is a Group 2 metal, so it has a charge of +2 → Mg²⁺
Sulfate is a polyatomic ion → SO₄²⁻
Since both ions have a charge of ±2, they combine in a 1:1 ratio, so the formula is:
➡ MgSO₄
Transition metals- have variable charges
1. Iron (Fe)
Fe²⁺ = Iron(II)
Fe³⁺ = Iron(III)
Examples:
FeCl₂ → Iron(II) chloride
FeCl₃ → Iron(III) chloride
2. Copper (Cu)
Cu⁺ = Copper(I)
Cu²⁺ = Copper(II)
Examples:
Cu₂O → Copper(I) oxide
CuO → Copper(II) oxide
3. Lead (Pb)
Pb²⁺ = Lead(II)
Pb⁴⁺ = Lead(IV)
Examples:
PbO → Lead(II) oxide
PbO₂ → Lead(IV) oxide
*Mn2 + NO3= Mn3NO2= manganese(II) nitrate
Electronegativity and Bond Polarity
Electronegativity- the ability of an atom to attract a shared pair of electrons towards itself
Polar covalent = unequal sharing of electrons in a bond.
1. Nonpolar Covalent Bond
Electrons are shared equally.
ΔEN < 0.4
Example: O₂ (Oxygen molecule)
Oxygen EN = 3.5
ΔEN = 3.5 – 3.5 = 0
Bond Type: Nonpolar Covalent
Visual:
O : O
(bonding electrons shared equally)
2. Polar Covalent Bond
Electrons are shared unequally.
ΔEN between 0.5 – 1.7
Example: H₂O (Water)
Oxygen EN = 3.5, Hydrogen EN = 2.1
ΔEN = 1.4 → Polar Covalent
Visual:
mathematica
CopyEdit
Hδ⁺ — Oδ⁻ — Hδ⁺
Oxygen pulls electrons more strongly → partial negative charge (δ⁻)
Hydrogens → partial positive charge (δ⁺)
3. Ionic Bond
Electrons are completely transferred.
ΔEN > 1.7
Example: NaCl (Sodium chloride)
Sodium EN = 0.9, Chlorine EN = 3.0
ΔEN = 2.1 → Ionic
Ionic Reaction:
Na → Na⁺ + e⁻
Cl + e⁻ → Cl⁻
Result: Na⁺Cl⁻ → Ionic bond
Avogadro number - Particles such as atoms, molecules, and ions are counted by the mole, which contains approximately 6.02 × 10^23 items. This value, known as Avogadro’s number.
Equations for chemical reactions
Balanced chemical reactions- they identify all the reactions and products involved
- they tell us the states of the substances involved in the reaction
-the quantities of the reaction and product
- the energy involved
A+B= AB combination reaction
AB= A+B decomposition reaction
AB + CD= AD + CB double replacement
Combustion reaction (burning a substance in oxygen)
Complete combustion produces 2 products, 1 carbon dioxide (CO2) 2. water (H2O) CO2+H2O
fuels hydrocarbons- substances made from hydrogen and carbon
Incomplete combustion produces carbon monoxide and water
CO + H2O
Reduction and Oxidation
Reduction- is a gain of electrons
Oxidation- is the loss of electrons
Redox- they occur simultaneously
As one substance loses an electron another substance gains those electrons
Neutral element loses an electron and becomes ion
Energy and Reaction
activation energy- the amount of energy required to break bonds in reactants (energy)
Endothermic reaction- energy is added ( absorbed) for the reaction to occur (feels cold)
Exothermic reaction- energy is given off or released for the reaction to occur ( heat released)
Collision- the reaction must collide
Orientation- must align properly for a reaction to occur
We can speed up the reaction by
increasing temp
increasing concentration of reactant
using catalist (facilitate reaction)
Gases Kenetic theory of gases
Gases are made up of small particles that move randomly
The atrractive forces between particles of a gas are minimal, they rarely bump into each other
The volume occupied by gases are larger than the volume of the gas particles themselves
Particles of a gas are constantly moving in a straight path
the average kinetic energy of gases is proportional to the average Kelvin temperature
Bolyles law: gas behavior can be described by measuring some attributes like their volume, temp, pressure, and amount (moles)
p1v1=p2v2
p= atmosphere (atm)
v= liters (ml)
pressure:mmHg = millimeters of mercury
Charles law= pressure and amount are constant
v1/t1=v2/t2
Gay-Lussac’s law= pressure and temperature
p1/t1=p2/t2
Standard temperature and pressure and molar volume (STP)
pressure = is the force exerted on the inner wall of the container by the particles of gas
Solubility
solution= solute + solvent
Solutions are also called homogeneous mixture
Alloy- mixtures of metals
solvent is larger quantity
solute- less quantity
Solution= like dissolves like
Miscibility- mixable in other words no separation between liquids
immiscible- mixture will separate (oil and water)
Equivalents= are used to measure electrolyte ions
are based on charges on the ions
Concentration is the amount of solute dissolved in a solution
dilute= solution that has less than the maximum amount
the universal solvent is water
Electrolyte= substance that can conduct an electric current
Solubility- the ability of a substance to dissolve in a solvent. it measures the amount of a substance dissolved in a solvent. Usually expressed in grams of solute in 100g H2O
Unsaturated- when we have less than the maximum amount of solvent in a solution
All nitrates are soluble (NO3)
Mass/mass concentration
m/m %= grams of solute/ volume of solution X 100
Mass/volume concentration
m/v%= grams of solute/ volume of solution X 100
Molarity = moles of solute/ liters of solution