Science Starter  What is the charge of the element magneiusm?  What is the charge of the magneiusm ion?  What is the formula and name of bonding magnesium ion to the chlorate ion?

Unit 7 Chemical Reactions Basic Chemical Reactions

What is a Chemical Reaction?  Chemical reactions are just the rearrangement of atoms.  There are 4 signs of chemical reactions. These include:  Formation of Precipitate  Color Change  Heat/Light  Gas Formation  Reactants react to produce products.  Reactants  Products  DO NOT FLIP THE ARROW! (we don’t read left to right, it doesn’t make sense, so DON’T DO IT! It gives us chemistry teachers headaches.)

Other Important Information About Chemical Reactions  Sometimes you will see some unique signs and symbols.  s, l, g, aq are just physical states (solid, liquid, gas, aqueous)  ∆ is the greek letter delta (means change) and is used to describe heat that is given to a reaction.  Sometimes things like a catalyst is used over the arrow to describe something that speeds up a chemical reaction.  It is not a reactant or a product.

Other important information  All new compounds still follow ALL of the naming and formula writing rules.  NEVER CARRY A SUBSCRIPT  If you do this, you will make the compound not neutral and that can ruin the following steps in the unit.  Know your diatomic elements (Mr. Br 2 I 2 N 2 Cl 2 H 2 O 2 F 2 ) and know their physical states!  Know basic physical states for items  H 2 O (l) is a liquid most of the time.  CO 2 (g), SO 2 (g), NO 2 (g), CH 4 (g)-common name is methane, NH 3 (g)- common name is ammonia are all gases.  Metals like JUST Ca(s), Na(s), Fe(s), Cu(s) are all solids.

5 Types of Chemical Reactions  Double Replacement  Single Replacement  Known a lot of the times as a redox reaction  (One item loses electrons while another species gains them)  Synthesis (combination)  Decomposition  Combustion

Double Replacement Examples  Double replacement reactions involve two ionic compounds that react.  This is where both the cation and anions of each chemical switch.  It is like two people dancing and bump into each other which cause them to switch partners halfway through the song.  Please note that you have to make the compounds neutral if you have to predict the products.  AB + CD  AD + CB  The order of the reactants or the products does not matter AS LONG AS YOU KEEP THEM AS REACTANTS AND PRODUCTS!

Single Replacement Examples  Single replacement involves a compound and a single element.  The compound is broken up by the other similar substance  Look at the single species and see if it could be a cation or anion. Then swap it with the ionic compound.  It is like a partner cutting into a couples dance.  Please note that you have to make the compounds neutral if you have to predict the products. Watch for diatomics!  AB + C  AC + B  C is an anion in this example.  AB + C  CB + A  C is an cation in this example.  The single species can be a metal or non-metal! I should get in on that…

Synthesis Examples  This is also known as a combination reaction.  Two or more species (whether they are a compounds or elements) form ONE SINGLE PRODUCT.  A+B  AB  Please note that you have to make the compounds neutral if you have to predict the products.  Keep an eye out for diatomics!

Decomposition Examples  One compound is broken down (decomposed) into two different pieces.  AB  A + B  Please keep note of diatomics!

Combustion Examples  A compound containing carbon AND hydrogen reacts with oxygen gas, O 2  When a compound is “ burned” it means there was a combustion reaction.  Products will ALWAYS BE CO 2 AND H 2 O  C x H y + O 2  CO 2 + H 2 O  You may also have other elements in your reactant compound other than C and H, such as nitrogen and sulfur. These will form new compounds based on what is “leftover” after you’ve created CO 2 and H 2 O.  C 2 H 5 SH + O 2  CO 2 + H 2 O + SO 2

Identifying the Reaction  From the following reactions, please classify them as SR, DR, S, D, or C:

TRY ME!  NaOH + KNO 3 → NaNO 3 + KOH  What type of reaction am I?  CH O 2 → CO H 2 O  What type of reaction am I?  Ca + NaBr → ____________+ _____________  What type of reaction am I?  __________ + __________ → Ca(OH) 2 + MgSO 4  What type of reaction am I?

Word Practice  Please write the chemical equation that matches the following scenarios: