Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes.
Vocabulary: calorimeter, chemical bond, endothermic, enthalpy, exothermic, Hess’s law
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. Two magnets are stuc...
1 two magnets are stuck together what might you have to do to get them to separate
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Lab 22: Student Exploration: Reaction Energy
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Vocabulary: calorimeter, chemical bond, endothermic, enthalpy, exothermic, Hess’s law
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. Two magnets are stuck together. What might you have to do to get them to separate?
Pull them apart
2. Suppose you held two magnets a short distance apart, then let go. What would happen?
Depends on which poles of the magnets were facing each other. If one was
positive and one was negative, they would be attracted to each other. If they
were either both positive or negative, they would repel.
3. Think about the magnets in terms of energy. In which case do you increase the potential
energy of the magnets? In which case do you increase the kinetic energy of the
magnets?
Kinetic energy increases if you were to move magnets with the same charge
towards each other because they are going to repel. Potential energy would
increase if they were different poles because they are attracted to each
other.
Gizmo Warm-up
Just like magnets, atoms of different elements are
attracted together to form chemical bonds.
Breaking these bonds requires energy. When a
new bond forms, energy is released and
temperatures rise. In the Reaction Energy Gizmo,
you will explore how the energy of chemical
bonding relates to temperature changes that occur
during chemical reactions.
To begin, check that Reaction 1 and Forward are selected. In this reaction, hydrogen (H2) and
oxygen (O2) react to form water (H2O). The reaction takes place inside a device called a
calorimeter. Inside the calorimeter, a small chamber holds the reactants. The rest of the
calorimeter is filled with water.
, 1. Click Play ( ). What happens?
Temperature increases, moving molecules.
2. How does the temperature change?
Increases
This study source was downloaded by 100000847097152 from CourseHero.com on 11-15-2022 12:00:01 GMT -06:00
Activity A: Get the Gizmo ready:
Energy of ● Check that Reaction 1 and Forward are
chemical bonds selected.
● Select the INVESTIGATION tab.
Introduction: The heat energy stored in a chemical system is called the enthalpy (H) of the
system. When atoms are joined by a chemical bond, energy must be added to pull them apart.
This increases the enthalpy of the system. When a chemical bond forms, energy is released as
shared electrons move into lower-energy orbitals. This causes the enthalpy to decrease.
Question: How can you predict how much energy is released in a chemical reaction?
1. Predict: In the warm-up activity, you observed how the reaction inside the chamber affected
the temperature of the surrounding water. Based on what happens to the surrounding water,
do you think heat energy (enthalpy) is absorbed in the reaction or released? Explain.
Heat is released because the surrounding water is absorbing the heat (which we
know because the temperature increases).
2. Observe: In the Gizmo, the energy required to break a chemical bond is modeled by placing a
molecule into a set of mechanical claws. Place one of the hydrogen (H2) molecules between
the claws, and press the Break bond.
A. What happens? The bond between the atoms is broken and energy is
absorbed.
B. Look under the Energy absorbed column of the table. How much energy was required to
break this bond?
436kJ/mol
Note: The energy is given here in units of kilojoules per mole (kJ/mol). This is the
energy, in kilojoules, required to break all of the H–H bonds in one mole of H2 gas.
C. Remove the hydrogen atoms from the claws and then break apart the other H–H
872kJ/mol
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