Chemical reactions

Chemical Reactions

Use Models to represent chemical reactions. Describe chemical reactions using equations. Investigate chemical and physical change.

Next Tuesday-Lab

• If you could bring in one bottle of Elmer’s glue, we will be able to do the lab on Tuesday!!! Thanks.

• I need it by Monday!

Chemical Reactions

• Vocabulary• Reactant-participate in the

reaction • Product-what is produced by the

reaction• Exothermic-Release energy • Endothermic-Absorb energy

Brain Storm

• With a partner-take 1 minute to make a list of chemical reactions that you witness or do every day.

•Chemical reactions Rearrange atoms

Synthesis-combines substances

•A + B AB

•2Na + Cl2 2NaCl

•You start with two separate substances and they combine to make something new.

Decomposition

•AB A + B

•2H2O 2H2 + O2

•Start with one substance and break it down into two.

•

Single Replacement Reaction

•AX + B AB + X

The “Scandalous” element steals away the Compounds partner and replaces it with itself.

Combustion Reaction

•Use oxygen as a reactant

• CH4 + 2O2 CO2 + 2H20

Double Replacement Reaction

•AX + BY AY + BX

•A reaction where two compounds appear to exchange ions

• Chemical Rxns (reactions) rearrange the atoms in an equation

• Occur when substances go through chemical changes to form new substances.

• Add energy to break bonds• Release energy to form bonds

1) ____ Ag2SO4 + ____ NaNO3

2) ____ NaI + ____ CaSO4

3) ____ HNO3 + ____ Ca(OH)2

4) ____ CaCO3

5) ____ AlCl3 + ____ (NH4)PO4

6) ____ Pb + ____ Fe(NO3)3

Signs of a chemical reaction

• Changes you can see•Formation of a gas, •Formation of a solid•Color Changes•Release of energy (heat/energy)

Law of Conservation of Mass/Energy • Energy is Conserved • The energy you start with is the same

energy that you end with just in a different form.

• Total amount of energy of reactants must always equal the total amount of energy in the products and their surrounding environment.

• Reactions that release energy are exothermic

• Reactions that absorb energy are endothermic

Energy and Reactions

• Reactions that release energy are exothermic-

• Examples-combustion reactions are always exothermic

• Products have less energy than the reactants.

Reaction Rates

•Anything that increases contact between particles will increase the rate of reaction.

•Most reactions go faster at higher temperatures

•Large surface area•Higher concentrations of

reactants react faster

•Higher pressure increases reaction rate

•Catalysts speed up reactions •Enzymes are biological

catalysts

Balancing Equations

• 1. Get yourself an unbalanced equation. I might give this to you, or I might make you figure it out.

• 2. Draw boxes around all the chemical formulas. Never, ever, change anything inside the boxes. Ever. Really. If you do, you're guaranteed to get the answer wrong.

• 3. Make an element inventory. How are you going to know if the equation is balanced if you don't actually make a list of how many of each atom you have? 

• 4. Write numbers in front of each of the boxes until the inventory for each element is the same both before and after the reaction. Whenever you change a number, make sure to update the inventory - otherwise, you run the risk of balancing it incorrectly. When all the numbers in the inventory balance, then the equation can balance.

• Example

• 1. __NaCl + __BeF2 --> __NaF + __BeCl2• 2. __FeCl3 + __Be3(PO4)2 --> __BeCl2 + __FePO4

• 3. __AgNO3 + __LiOH --> __AgOH + __LiNO3

• 4. __CH4 + __O2 --> __CO2 + __H2O

• 5. __Mg + __Mn2O3 --> __MgO + __Mn

• Bill Nye

Exit Ticket

• Predict what products will be found in

a. The decomposition of HgOb. Calcium Carbonate and

Hydrochloric Acid (HCL) reacting together.

Exit ticket

• List 3 signs that could indicate that a chemical reaction is taking place.