Ch. 4 - Chemical Reactions
Standards covered in this chapter:
7.PS1.4 - Analyze and interpret chemical reactions to determine if the total number of atoms in the reactants and products support the Law of Conservation of Mass.
Important Vocabulary:
Physical Change - A change that alters the form of the appearance of a material but does not make the material into a new substance.
Chemical Change - A change in which one or more substances combine or break apart to form new substances.
Reactants - A substance that enters into a chemical reaction.
Product - A substance formed as a result of a chemical reaction.
Exothermic reaction - A reaction that releases energy, usually in the form of heat.
Endothermic Reaction - A reaction that absorbs energy.
Chemical equation - A short, easy way to show a chemical reaction using symbols.
Law of Conservation of Mass - The principle that the total amount of matter is neither created nor destroyed during any chemical or physical change.
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.
Enzyme - A type of protein that speeds up a chemical reaction in a living thing.
Summary
Changes in matter can be described in terms of physical changes and chemical changes. Chemical reactions involve changes in properties and changes in energy that you can often observe. A chemical equation tells you the substances you start with in a reaction and the substances that are formed at the end. In a chemical reaction, all of the atoms present at the start of the reaction are present at the end of the reaction. All of the chemical reactions need a certain amount of activation energy to get started. Factors that can affect rates of reactions include surface area, temperature, concentration, and the pressure of catalysts and inhibitors.
A chemical change is where one or more combine or break apart to form new substances.
Physical changes alter the appearance and form of materials, but do not make them into new substances.
