GEN CHEM 1 | Physical and Chemical Change and Chemical Reactions

Physical Change

change in physical properties and not its chemical identity nor composition, does not lead to the formation of new susbances

Intensive Properties

inherent physical properties, does not depend on amount of substance (color, temperature, density, solubility)

Extensive Properties

depends on the amount of substance (size, volume, weight)

Melting

solid to liquid

Freezing

liquid to solid

Evaporation

liquid to gas

Condensation

gas to liquid

Deposition

gas to solid

Sublimation

solid to gas

Chemical Change

change in chemical composition through rearrangement of atoms into a new substances with significantly different properties; substances reacts and produces a new substances

Evidences/Indicators of Chemical Change

• evolution of gas - bubbles in reaction

• evolution of heat - release or absorption of heat

• color change

• odor production

• formation of precipitate - insoluble solids formed

Reactants

substances that are used in the reactions, written on the left side of reaction

Products

substances that formed from the reaction, written on right side of reactions

Phases

indicated by (s) for solid, (l) for liquid, (aq) for aqueous solution, or (g) for gas on the right of the involves substances to indicate their phases

Plus Sign

indicate combination of substance

Arrow

to form or to yield

Coefficients

the big number that indicates the number of molecules of the substances; always a whole number

Subscripts

the smaller number that indicates the number of atoms of a certain element; always a number

Diatomic Molecules

elements that naturally appear in nature as a gas with two combined atoms

Diatomic Elements

Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine, Bromine

Combination Reaction | Definition

also known as synthesis reaction, multiple reactants combine to form a single product

Combination reaction | Formula

X + Y → XY

Decomposition Reaction | Definition

As the opposite of the combination reaction, a single compound breaks into two or more simpler substances

Decomposition Reaction | Formula

XY → X + Y

Single Displacement Reaction | Definition

also known as a substitution reaction, a more reactive element displaces a less reactive element from its aqueous salt solution

Single Displacement Reaction | Formula

X + YZ → XZ + Y

Double Displacement Reaction | Definition

also known as a metathesis reaction, ions get exchanged between two reactants which a new compound

Double Displacement Reaction | Formula

XY + ZA → XZ + YA

Monatomic Ions

Ions based on elements in groups 1A, 2A, 3A, 5A, 6A, 7A

Cations

Ions found in groups 1A, 2A, and 3A

Anions

Ions found in groups 5A, 6A, and 7A, has a suffix -ide

1A Cations

has a +1 charge; examples include Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Caesium (Cs), Francium (Fr)

2A Cations

has a +2 charge; examples include Berillium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), Radium (Ra)

3A Cations

has a +3 charge; examples include Boron (B) and Aluminum (Al)

5A Anions

has a -3 charge; examples include Nitride (N), Phosphide (P), Arsenide (As)

6A Anions

has a -2 charge; examples include Oxide (O), Sulfide (S), Selenide (Se), Telluride (Te)

7A Anions

has a -1 charge; examples include Fluoride (F), Chloride (Cl), Bromide (Br), Iodide (I)

8A Atoms

have zero charge

Polyatomic Ions

Compounds that have an overall charge

Criss Cross Rule

In ionic bonds, the ion’s respective charges become the other’s subscripts

Combustion Reaction | Definition

the reaction behind burning

Combustion Reaction | Formula

C_xH_y + O₂ (g) → CO₂ (g) + H₂O (g)

Law of Conservation of Mass

Proposed by French chemist Antoine Lavoisier, mass in an isolated system can neither be created nor destroyed but can change in form. This means the mass of reactants is equal to the mass of the products.

Balancing Chemical Reactions

due to the law of conservation of mass, balancing equations helps one better understand stoichiometric calculations through the correct ratio of reactants and products

Balancing Chemical Reactions Guidelines

1. Subscripts or the formula itself cannot be changed

2. Coefficients are the only numbers that can be changed, and it must be a whole number

3. Each element must have an equal number of atoms on both the reactant and product sides