Chapter Five chemistry note

·         One mole is the atomic weight in grams. One mole of an element contains Avogadro’s number of atoms. To know how many particles there are, multiply the number by Avogadro’s number.

·         Molar mass = weight of all included elements

·         Moles to grams: moles X molar mass

·         Grams to moles: g/mm

·         The subscripts also state the number of moles in each element

·         Physical change alters the appearance of a substance but not its formula

·         In a chemical change, the reacting substances change into new substances that have different formulas and different properties

·         A chemical reaction always involves chemical change as bonds between the atoms in the original substances are broken and new bonds are formed.

·         A chemical equation tells us the materials we need and the products that will form in a chemical equation. In an equation, the formulas of the reactants are written of the left of the arrow and the formulas of the products on the right. A plus sign is used when two or more formulas are involved.

·         Since atoms cannot be destroyed or changed, the equation must balance out on the other side.

·         In a combination reaction, two or more elements or compounds bond to form one product.

·         In a decomposition reaction, a reactant splits into simpler products.

·         In a single replacement reaction, a reacting element switches place with an element in the other reacting compound.

·         In a double replacement reaction, the positive ions in the reacting compounds switch places. You have to look at the charges to know which ones to change.

·         In an oxidation reduction reaction, electrons are transferred from one substance to another. If one gains than the other one must lose.

·         Oxidation is the loss of electrons

·         Reduction is the gain of electrons

·         In any chemical reaction, the total amount of matter in the reactant is equal to the total amount of matter in the products.

·         The coefficients are also moles.

·         Three conditions required for a reaction to occur:

o   Collision

o   Orientation- the reactants must align properly to break and form bonds

o   Energy

·         The heat of reaction is the energy difference between reactants and the products.

·         Exothermic reactions give off heat

·         Endothermic reactions need heat

·         The rate of reaction is measured by the amount of reactant used up or the amount of product formed in a certain period of time. The more heat (energy) used, the faster the rate.

·         The rate of reaction also increases when reactants are added because there’s more collision going on.

·         Adding a catalyst will also speed up the reaction because it lowers the energy of activation. Like digging a tunnel through a mountain instead of going over it.