8-Ionic and Molecular Compounds

A chemical change…

occurs when starting substances are converted into one or more completely new substances with entirely different physical and chemical properties (like shiny silver turning into black tarnish, or gray iron turning into reddish-brown rust).

During a reaction, the chemical bonds holding the reactants together…

are broken, the atoms are shuffled around, and new bonds are formed to create the products.

The Law of the Conservation of Mass States that…

matter cannot be created or destroyed in a chemical reaction.

When balancing chemical equations never change the small subscript numbers inside a chemical formula (like the 2 in H2), because…

because changing the subscript changes the actual identity of the substance. You can only change the coefficients in front.

Two or more separate elements or simple compounds bond together to form…

one single product (Combination aka synthesis)

in 2Mg+O2—→2MgO

The O is a diatomic molecule, meaning that two oxygen molecules are bonded together and During the chemical change, the O2 bond breaks. Each oxygen atom gains two electrons from a magnesium atom and because Mg has a charge of 2+ and O has a charge of -2 they attract each other to from MgO, creating a stable compound and a 1:1 ratio.

The exact opposite of combination where….

One single reactant splits apart into two or more simpler products, usually triggered by heat. (Decomposition)

A (BLANK) steps in and (BLANK) an element already inside a compound.

an aggressive, uncombined element; switches places with (known as a single replacement)

Decompostion example….

2H2O—>2H2+O2

Single replacement example…

Zn+2HCl—>ZnCl2+H2

The positive ions of two different ionic compounds….

swap partners entirely, often forming a solid powder called a precipitate (a double replacement)

Example of a double replacement

NaOH+HCl—>NaCl+H2O

A carbon-containing compound (a fuel like methane, CH subscript 4, or propane (C3H8) that burns in the presence of oxygen gas (O2)

Combustion

A+B—>AB

Combination/synthesis

AB—>A+B

Decomposition

A+BC—→B+AC

Single replacement

AB+CD—> AD+CB

Double replacement

Hydrocarbon+O2—→Co2+H2O

Combustion

An oxidation-reduction reaction

any reaction where electrons are transferred from one substance to another. One substance loses negative electrons, which means another substance must immediately grab them. They always happen at the same time.

Oxidation is a ……and reduction is a ….

1.) is a loss of electrons 2.) is a gain of electrons

Metals

Tend to lose electrons easily to form positive ions, meaning metals are oxidized.

Nonmetals

Tend to grab electrons to form negative ions, meaning nonmetals are reduced.

The charge goes up (becomes more positive) because it lost negative electrons.

Oxidation

The charge goes down (is reduced, becoming more negative) because it gained negative electrons.

Reduction

Cu²+2e^- →Cu^0

Reduction

Zn^0—>Zn²+2e^-

Oxidation