Upload
jesse-garrett
View
219
Download
0
Embed Size (px)
Citation preview
CHEMICAL REACTIONS
Chapters 7 and 8
What is a chemical reaction A chemical reaction (a.k.a, chemical
change) is a process in which one or more substances change into new substances.
This happens when atoms or molecules of the starting substances collide, bonds break, and new bonds are formed. ATOMS ARE NOT CREATED NOR DESTROYED. They are merely rearranged.
Evidence of a chemical reaction
Not every chemical reaction is accompanied by observable evidence, however many reactions are. Some signs that a chemical reaction has taken place are:
temperature changeproduction of heat and lightcolor changeproduction of an odorFormation of a precipitate (solid forming)Formation of bubbles
Representing chemical reactions
Chemical reactions are represented with “equations”. All equations have reactants on the left and products on the right, with an arrow separating the two. This arrow says “reacts to produce” or “yields”.
Ex: reactant 1 + reactant 2 product 1 + product 2
Word equations – use names of reactants and products only
Ex: iron + chlorine iron (III) chloride
Skeleton Equations – use correct chemical formulas for the reactants and products
Ex: Fe + Cl2 FeCl3
Balanced Chemical Equations – use correct chemical formulas for the reactants and products AND coefficients to reflect the law of conservation of mass
Ex: 2Fe + 3Cl2 2FeCl3
Other symbols often found in chemical equations (s) = solid (l) = liquid (g) = gas (aq) = aqueous (dissolved in water) Δ (over the arrow) = reactants must be
heated ↑(after a product) = produced as a gas ↓(after a product) = produced as a solid
precipitate = reactants and products are in equilibrium
Some examples Solid iron reacts with chlorine gas to produce
solid iron (III) chloride.
2Fe(s) + 3Cl2(g) 2FeCl3(s)
Aqueous solutions of sodium carbonate and calcium chloride react to produce aqueous sodium chloride and solid calcium carbonate.
Na2CO3(aq) + CaCl2(aq) 2NaCl(aq) + CaCO3(s)