Science Exam Revision Semester 2 - Chemical Reactions

Reactants

A starting material in a chemical reaction

Products

The elements or compounds produced by a chemical reaction.

Chemical Reaction

the process by which one or more substances change to produce one or more different substances

Chemical change

A change in matter that produces one or more new substances

Law of Conservation of Mass

Matter is not created nor destroyed in any chemical or physical change

Chemical Formula

A combination of chemical symbols and numbers to represent a substance

Coefficient

A number in front of a chemical formula in an equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction.

Subscript

A number in a chemical formula that tells the number of atoms in a molecule or the ratio of elements in a compound

word equation

an equation in which the reactants and products in a chemical reaction are represented by words

Chemical Equation

A representation of a chemical reaction that uses symbols to show the relationship between the reactants and the products

balanced chemical equation

chemical equation with the same number of atoms of each element on both sides of the equation

endothermic reaction

A reaction that ABSORBS energy in the form of heat

exothermic reaction

A reaction that releases energy in the form of heat

decomposition reaction

a reaction in which a single compound breaks down to form two or more simpler substances

synthesis reaction

a reaction in which two or more substances combine to form a new compound

single replacement reaction

a chemical change in which one element replaces a second element in a compound

double replacement reaction

a chemical change that involves an exchange of positive ions between two compounds

combustion reaction

a chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light

precipitation reaction

a reaction in which an insoluble substance forms and separates from the solution

soluble

capable of being dissolved

Insoluble

incapable of being dissolved

precipitate

A solid that forms from a solution during a chemical reaction.

reaction rate

the rate at which reactants change into products over time

Temperature & reaction rate

usually the higher the temperature the faster the reaction rate

Concentration & Reaction Rate

the higher the concentration of starting materials, the more rapidly the reaction takes place (more collisions taking place). as more reactants are consumed the rate of reaction slows down

Agitation

Stirring up the reactants - increasing the reaction rate

catalyst

substance that speeds up the rate of a chemical reaction

Enzymes

Catalysts for chemical reactions in living things