Basic Chemistry for Biology Chemical Bonds

What is a chemical reaction? “A chemical reaction is a process that leads to the transformation of one set of chemical substances into another.” Wikipedia.org …so, how do chemicals get transformed?? By the breaking and re-forming of chemical bonds

…so, why do I care? Because of the LAW OF CONSERVATION OF MATTER AND ENERGY “Matter and energy can be neither created nor destroyed but only transformed (changed from one form to another)” Antoine Lavoisier And what does THAT mean? You can’t end up with more or less substance than you start with!

Chemical Equations H2 + O2  H2O Chemical equations MUST be balanced They must have the same number of atoms of each element on each side of the equation H2 + O2  H2O Subscript – tells how many atoms of each element in a compound SUBSCRIPTS CAN’T BE CHANGED!!

Balancing Equations 2 H2 + O2  2 H2O Since you can’t change the subscripts, you must be able to use some kind of number as a multiplier 2 H2 + O2  2 H2O Coefficient – just like in math, a coefficient multiplies everything that follows Now the equation is balanced!

And what does this mean? The entire reaction requires To produce 2 molecules of hydrogen (2 H2) = 4 atoms H 1 molecule of oxygen (O2) = 2 atoms O To produce 2 molecules of water (2 H2O) = 4 atoms H and 2 atoms O Without losing any matter