Chemical Reactions

Key Concepts A physical change, such as a state change or dissolving, does not create a new substance, but a chemical change does. In a chemical reaction, the atoms and molecules that interact with each other are called reactants. In a chemical reaction, the atoms and molecules produced by the reaction are called products. In a chemical reaction, only the atoms present in the reactants can end up in the products. No new atoms are created, and no atoms are destroyed. In a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.

What is a chemical reaction? In a chemical reaction, the molecules in the reactants interact to form a new substance. A chemical reaction causes a chemical change. Other processes, like dissolving or change of state is a physical change, in which no new substance is formed.

True or false Adding salt to water is a chemical reaction. Burning a candle is a chemical reaction.

Candle and jar demo We lit a candle and it was a chemical reaction. What are the reactants in this chemical reaction? What are the products of this reaction? Why did the flame go out when we placed the jar on top of the candle?

Chemical reaction from candle Wax is made of up hydrocarbons (long molecules carbons and hydrogens) Oxygen that we breath is 2 molecules of O2

How to read a chemical equation The little number written at the lower right after an atom (subscript) tells how many of that atom are in the molecule. The big number written in front of a molecule (coefficient) shows how many of that molecule there are. All the atoms in the products come from the atoms in the reactants.

How the molecules break apart and how to balance the equation http://www.middleschoolchemistry.com/multimedia/chapter6/lesso n1#chemical_reaction_methane No new atoms are created, nor destroyed.