chemical reactions and equations class notes. review from last class what types of changes can occur...
TRANSCRIPT
Chemical Reactions and Equations
CLASS NOTES
Review from last class
• What types of changes can occur as a result of chemical reactions? – Can you give an example?– Physical changes!
– Chemical changes!
What is involved in a chemical reaction?
• There are two parts to a chemical reaction:– Reactants and Products
• Reactants are those substances you begin with • Products are the substances formed by the
reactionreactant1 + reactant2 products
• For example:hydrogen + oxygen water
Chemical equations• Chemical reactions are written using equations, with
reactants on one side and products on the other:• Word equations!
e.g. sodium + chlorine sodium chloride carbon + oxygen carbon dioxide calcium + oxygen calcium oxide
• Usually written with chemical formulas (symbols):Ex. Na + Cl NaCl
C + O₂ CO₂Ca + O CaO
Chemical equations continued…• The number of atoms on one side of the
chemical equation is equal to the other side:• Reactant1 + reactant 2 product is the same as equals, or produces
Endothermic and Exothermic Reactions
• In a chemical reaction, bonds in the reactants break and new bonds form in the products
• Breaking and creating bonds requires energy• Two types of chemical reactions:– Absorbs energy = endothermic
(energy in = ENtrance)– Releases energy = exothermic
(energy EXits)