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Core Chemistry Name: __________________________ Molecular Model Activity Date: _______________ Hour:________ Balancing Equations with Molecular Models LAW OF CONSERVATION OF MATTER: ❑ ATOMS ARE NEITHER CREATED NOR DESTROYED DURING A CHEMICAL REACTION. ❑ The bonds in reactant molecules break and these atoms rearrange to make new bonds with different atoms resulting in a new compound or compounds. Example: ______ H 2 + ______O 2 → ______ H 2 O Element # atoms on reactant side (original) # atoms on product side (original) # atoms on reactant side (final, balanced) # atoms on product side (final, balanced) Hydrogen Oxygen For each of the chemical equations written below, you will perform the following tasks: 1. Pick a partner. Decide who is Partner A: ________________________ and who is Partner B: ______________________ 2. Using the molecular model kit, build the molecules (use color guide to ﬁgure out which spheres to use.) Partner A: Build the reactants for the original reaction. Look at the number of each atom on the reactants side (unbalanced) and write these numbers down. Take the needed atoms and bonds (ex: H 2 and O 2 : take 2 H and bond them together, and 2 O and bond them together) Partner B: Build the products for the original reaction. Look at the number of each atom on the products side (unbalanced) and take the needed atoms and bonds (ex: H 2 O: take 2H and one O and bond them together with O in the middle) 3. Compare the number of each atom on the reactant side to the product side. If they are the same, you're done. If not, you need to adjust quantities. Remember, atoms bonded to each other must stay that way! If you are dealing with O 2 , you can't just add an additional single O atom – they add in pairs. (ex: Oxygen is not balanced. Partner b builds a second H 2 O molecule on the product side.This causes H on the reactant side to be unbalanced, so Partner a builds a second H 2 molecule)

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Core Chemistry Name: __________________________Molecular Model Activity Date: _______________ Hour:________

Balancing Equations with Molecular Models

LAW OF CONSERVATION OF MATTER:❑ ATOMS ARE NEITHER CREATED NOR DESTROYED DURING A CHEMICAL REACTION. ❑ The bonds in reactant molecules break and these atoms rearrange to make new bonds with different

atoms resulting in a new compound or compounds.

Example: ______ H2 + ______O2 → ______ H2O

Element # atoms on reactant side (original)

# atoms on product side (original)

# atoms on reactant side (final, balanced)

# atoms on product side (final, balanced)

HydrogenOxygen

For each of the chemical equations written below, you will perform the following tasks:1. Pick a partner. Decide who is Partner A: ________________________

and who is Partner B: ______________________ 2. Using the molecular model kit, build the molecules (use color guide to figure out which spheres to

use.) Partner A: Build the reactants for the original reaction. Look at the number of each atom on the reactants side (unbalanced) and write these numbers down. Take the needed atoms and bonds (ex: H2 and O2: take 2 H and bond them together, and 2 O and bond them together)

Partner B: Build the products for the original reaction. Look at the number of each atom on the products side (unbalanced) and take the needed atoms and bonds (ex: H2O: take 2H and one O and bond them together with O in the middle)

3. Compare the number of each atom on the reactant side to the product side. If they are the same, you're done. If not, you need to adjust quantities. Remember, atoms bonded to each other must stay that way! If you are dealing with O2, you can't just add an additional single O atom – they add in pairs.(ex: Oxygen is not balanced. Partner b builds a second H2O molecule on the product side.This causes H on the reactant side to be unbalanced, so Partner a builds a second H2 molecule)

4. Continue until the number of each atom on the reactants side is equal to the number of each atom on the products side. All atoms of the reactants rearrange to create the products – there should be the same number of everything, including bonds!

5. Balance the equation by writing the correct coefficient in front of each reactant and product of the chemical equation.

YOUR TURN: Balance the following equations by building models for the reactants and products according to the above instructions. Fill in the table as you go. When finished, write in the coefficients for the balanced equations. Get teachers initials at the end of each problem with molecular structures built.1. _____CH2 + _____H2 → _____C2H6

Element # atoms on reactant # atoms on product # atoms on reactant # atoms on product