Stop Motion Enthalpy Change Lab (No Googling)

1. Write the balanced equation for your reaction and have the instructor check it:

2. Determine and draw the Lewis structures for all the molecules in your reaction and have the instructor check your work:

3. Build the reactant models for the reactants using the models provided.

4. Determine the energy for bond breaking (endothermic). Using a Sharpie marker, write the energy on a sticky note.

5. Determine the energy for bond forming (exothermic). Using a Sharpie marker, write the en-ergy on a sticky note.

6. Determine ΔH for the reaction. Using a Sharpie marker, write the energy on a sticky note.

7. Create a stop motion video using the Stop Motion App for the iPad or iPhone.

8. The video should show collision of molecules, bond breaking (with energy), bond forming (with energy) and ΔH for the reaction. Adjust the speed of the movie so that the energy and the reaction are legible.

Teacher instructions:

Assign each group a reaction:

A. Hydrogen gas reacts with oxygen gas to form water.

B. Carbon (graphite) reacts with oxygen gas to form carbon monoxide.

C. Nitrogen gas reacts with hydrogen gas to form ammonia.

D. Hydrogen peroxide decomposes into water and oxygen gas.

Provide each group with the proper model parts (students could do this if there is enough time):A. 4 white hydrogen atom centers, 2 red oxygen atom centers, 4 short bond tubes, 2 long bond

tubesB. 2 black carbon atom centers, 2 red oxygen atom centers, 6 long bond tubesC. 2 blue nitrogen atom centers, 6 white hydrogen atom centers, 6 short bond tubes, 6 long

bond tubesD. 4 white hydrogen atom centers, 4 red oxygen centers, 6 short bond tubes, 2 long bond

tubes

Key:A. 2H2 + O2 → 2H2O ΔH = (432 x 2 + 498) - (467 x 4) = 1362 - 1868 = - 506 kJ

Lewis Structures:

B. 2C + O2 → 2CO ΔH = ( 498) - (1070 x 2) = 498 - 2140 = -1642 kJ

Lewis Structures:

C. N2 + 3H2 → 2NH3 ΔH = (945 + 432 x 3) - (391 x 6) = 2241 - 2346 = -105 kJLewis Structures:D. 2H2O2 → 2H2O + O2 ΔH = (467 x 2 + 204) - (467 x 4 + 498) = 1138 - 2366 = -1228 kJ

Lewis Structures:

H HH HH HH

H OO OO OO O

O OO OO O C OC OC O

N NN NN N H HH HH H HH O

HH

H NHOH O

C C C

Example Stop Motion Video for Reaction C (Student work: these students switched the bond breaking enthalpy with the bond forming enthalpy):