Ready... Set..... React!

Today was the start of our chemical reaction unit. I am very excited for this unit because it seems like it will not be as bad as the last one.
We started off today talking about what a chemical reaction is a signs to look for:

1. color change
2. a solid forms
3. bubbles form
4. heat and/or a flame is produces, or heat is absorbed
• exothermic (gets hot)- energy leaves the reaction (-)
• Energy is written as a product
• endothermic (gets cold)- energy goes into the reaction (+)
• Energy is written as a reactant

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After we figured out whether a reaction was chemical or not, we had to figure out the chemical equation.
EX: CH₄(g) + 2O₂ (g) --> CO₂(g) + 2H₂O(g)

•  CH₄(g) + 2O₂ (g) = reactant
• CO₂(g) + 2H₂O(g) = product
• --> = yields sign
• (g) = state of reactant/product

When writing the equation you must make sure all the atoms on the left side are the arrow are balanced on the right side of the arrow.

CH₄ + O₂ ---> CO₂ + H₂O

 This Chemical equation is not balanced! What do we do?

***********Start with the CHO method (Carbon-Hydrogen-Oxygen)**********

Looking at the carbon: 1=reactant; 1= product (we dont have to change anything there since they are balanced)

Looking at the Hydrogen: 4= reactant; 2=product (we would have to add a coeffiecnt of 2 in front of the H on the product side to balance it on both sides, leave 4=reactant; 4=product)

Lastly, Looking at the Oxygen: 2=product 4=product since there is 2 oxygen in CO2 and with the added coeffient for Hydrogen the 2 is distributed to the oxygen which adds two more (we would have to had a coeffient of 2 to the O2 on the reactant side to balance the equation)

Leaving us with an equation of:

CH₄ + 2O₂ ---> CO₂ + 2H₂O

We also learned about combustion. Three main things you should know:

1. always react with oxygen
2. combustion of a hydrocarbon always produces carbon dioxide and water
3. Use CHO method when balancing

If you need help with anything from above there are links below to videos/websites that might help:
Chemical vs Physical Reactions (website) (video)
Balancing Chemical Equations (website) (video)

Quiz Yourself:
Chemical vs Physical Change Quiz
Balancing Equations