Unit 12: Chemical Reactions
This week in chemistry we learned all about chemical reactions including the different kinds of chemical reactions, how they happen, if they will happen, and how to balance the chemical equation to make them happen. Balancing a chemical reaction isn't as easy as it seems, it takes time and practice but with help from labs like the Nail Lab learning about chemical reactions and formulas became a lot easier.
- Basic Things to Know About Reactions: When you first start a reaction the materials you start with are called the reactants and the material(s) you end with are called the product(s). There are many symbols that go along with knowing how a chemical reaction takes place. Some of these symbols include (+) which means used to separate 2 reactants or 2 products, (an arrow) which means used for reversible reactions, and (aq) which means aqueous solution; the substance is dissolved in water.
- Diatomic Molecules: Diatomic molecules are specific elements that occur in nature in groups rather than separate. These elements include Br2, I2, N2, H2, O2, and F2. These elements are commonly known as the "heavenly 7".
- How to Balance a Chemical Equation: Balancing a chemical equation is not always the easiest thing but with practice it becomes much easier. The first thing to know when balancing the equation is that the equation had to have equal numbers of each element in the reactants an din the products. You must write the "skeleton equation" first then count the number of atoms on the reactant side and balance it on the product side. Remember never to change subscripts and balance of element at a time and you will do fine!
- How to Know a Chemical Reaction is Taking Place: There are 5 simple things you need to remember to know a chemical reaction is taking place. 1.) a temperature change (+q) means colder and (-q) means warmer, 2.) a color change, 3.) an odor, 4.) gas bubbles, 5.) a formation o f a solid (precipitate).
Types of Chemical Reactions
- Synthesis Reactions: A synthesis reaction is when 2 or more substances react to produce a single product. If two elements react then it is always a synthesis reaction. When there is a synthesis reaction remember there will be a single ionic product.
- Combustion Reaction: A combustion reaction is when an element or compound reacts with oxygen producing energy in the form of heat or light. O2 will always be a reactant and another reactant is typically hydrocarbon. Some but not all combustion reactions are also synthesis reactions. This picture is an example of a combustion reaction because its product results in heat and light.
Tips to balancing Combustion Reactions: 1.) Place a "2" in front of the hydrocarbon, 2.) balance the C on each side, 3.) go back and balance H, 4.) balance O2 last, 5.) simplify coefficients if you can.- Decomposition Reactions: A decomposition reaction is when a single compound breaks down into 2 or more elements or compounds. It is also the opposite of a synthesis reaction.
- Single Replacement Reactions: A single replacement reaction is when one element switches places with another element in a compound. An example would be A + BX (arrow) AX + B.
- To know if one element will replace another we use the Activity Series chat. Activity decreases as you go down the row.
- Double Replacement Reactions: A double replacement reaction is an exchange of ion between 2 compounds. The cations will stay in place and the anions with switch places. This reaction usually takes place in aqueous solutions. A double replacement reaction will produce water, a solid, or a gas.
- We know a reaction will take place if it is soluble which means both reactants must be able to dissolve in water and dissociate into their ions. One product of the reaction must be insoluble.
Nail Lab
When doing the nail lab we first mass out are reactants including the nail and copper chloride. After filling the beaker with the copper chloride and letting the nails sit in there for a few days we observed that copper was starting to form on the once clean nail. We know a chemical reaction took place because there was a color change of the copper chloride and a solid forming on the nail. We determined that the reaction was a single replacement reaction because one element switched places with another element in the compound. This nail lab helped me see and observe in depth what a real chemical reaction looked like.
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