Science Assessment ~ Items ~ AP033006

A family decides to put a hummingbird feeder in their backyard to attract more hummingbirds. Hummingbirds, like many animals, can get energy by eating sugars such as common table sugar known as sucrose. So, they fill the hummingbird feeder with a mixture of sucrose and water.

Hummingbird and feeder by Dorian Wallender on flickr (CC BY-SA 2.0)

Sucrose molecules inside the hummingbird will react with oxygen molecules that the hummingbird breathes in to form carbon dioxide molecules and water molecules. Your task is to explain the energy changes that occur when a hummingbird uses sucrose to get energy. First, think about the potential energy difference between the reactant molecules (sucrose and oxygen) and the product molecules (carbon dioxide and water).

1. In order for the hummingbird to get energy from this chemical reaction, how must the potential energy of the reactant molecules (sucrose and oxygen) compare to the potential energy of the product molecules (carbon dioxide and water)?

A. The reactant molecules must have more potential energy than the product molecules.

B. The reactant molecules must have less potential energy than the product molecules.

Next, you will make a diagram to illustrate the energy changes that take place during the chemical reaction. Below are several different diagrams. The bars in the diagrams represent the potential energy associated with the chemical reaction system at three times:

The initial state before the oxygen and sucrose molecules have reacted,
A hypothetical intermediate state* where all the atoms are separated, and
The final state after the carbon dioxide and water molecules have formed.

(*During the reaction, atoms are separating and coming together to form new molecules. There is never a time when they are all completely separated at the same time. It is shown that way here to simplify the diagrams.)

2. Which of the diagrams best shows the potential energy changes of the chemical reaction system during the reaction between sucrose and oxygen molecules?

A.
B.
C.
D.

Now, use your diagram to help explain the energy changes that occur during the chemical reaction between sucrose and oxygen.

3. How does the amount of energy in the chemical reaction system change when going from the initial state to the intermediate state? In your explanation, be sure to write about energy inputs or outputs to the chemical reaction system.

4. How does the amount of energy in the chemical reaction system change when going from the intermediate state to the final state? In your explanation, be sure to write about energy inputs or outputs to the chemical reaction system.

5. Given that there are attractive forces between atoms that make up the molecules involved in the chemical reaction, explain why the energy of the chemical reaction system changes when the arrangement of atoms changes (for example, when going from molecules in the initial state to separated atoms in the intermediate state and going from the intermediate state to different molecules in the final state).

Details
Performance
NGSS

Topic: 3D Energy Tasks
Scoring Rubric: Q1; Student selects answer choice A

A. The reactant molecules must have more potential energy than the product molecules.; Q2; Student selects answer choice B; Q3; 1. Student makes a claim

The amount of energy in the system will increase.

2. Student states or uses general science ideas

A molecule has less energy (is more stable) than the same set of atoms separated (i.e., water and carbon dioxide molecules are more stable than separate carbon, hydrogen, and oxygen atoms). [energy of molecules vs. atoms]

Energy is required to break bonds between atoms (i.e., breaking the carbon/carbon bonds in sucrose requires energy). [energy and bond breaking]

3. Student uses crosscutting concepts about the flow of energy

There is an initial input of energy into the system when going from the initial state to the intermediate state.; Q4; 1. Student makes a claim

The amount of energy in the system will decrease.

2. Student states or uses general science ideas

A molecule has less energy (is more stable) than the same set of atoms separated (i.e., water and carbon dioxide molecules are more stable than separate carbon, hydrogen, and oxygen atoms). [energy of molecules vs. atoms]

Energy is released when bonds between atoms form (i.e., energy is released when hydrogen and oxygen atoms bond to form water molecules). [energy and bond making]

3. Student uses crosscutting concepts about the flow of energy

There is an output of energy from the system when going from the intermediate state to the final state.; Q5; 1. Student either states or uses a general science idea

A molecule has less energy (is more stable) than the same set of atoms separated (i.e., water and carbon dioxide molecules are more stable than separate carbon, hydrogen, and oxygen atoms). [energy of molecules vs. atoms]

When two objects interacting through a force field change relative position, the energy stored in teh field is changed (i.e., when the atoms get further apart, there is more energy in the system). [links energy and arrangement of atoms]

2. Student uses reasoning to link science ideas to the claim

The amount of energy in a chemical reaction system depends on how the atoms are arranged because the attractive forces pull the atoms together, which causes the potential energy of the system to be greater when the atoms are farther apart and less when the atoms are closer together

OR

The amount of energy in a chemical reaction system depends on how the atoms are arranged because the attractive forces work to pull the atoms together which causes molecules to have less energy/be more stable than the same set of atoms separated.

Percent of Points Earned

Chart showing distrubtion of responses for Item AP033006

Points Earned

	Avg. Earned	Possible	Percent
Q1	0.49	1	49%
Q2	0.2	1	20%
Q3	0.2	3	7%
Q4	0.3	3	10%
Q5	0.03	2	2%

Overall Task Difficulty

	Total Points Earned	Total Points Possible	Total Percent
	1.22	10	12%

n = 213

Note: The total percent is a weighted average based on the total number of points earned divided by the total number of points possible.

Science and Engineering Practices: SEP2 Develop and/or use multiple types of models to provide mechanistic accounts and/or predict phenomena, and move flexibly between model types based on merits and limitations.
SEP2 Use a model to predict the relationships between systems or between components of a system.
Crosscutting Concepts: CC5 Changes of energy and matter in a system can be described in terms of energy and matter flows into, out of, and within that system.
Disciplinary Core Ideas: PS1.B Chemical processes, their rates, and whether or not energy is stored or released can be understood in terms of the collisions of molecules and the rearrangements of atoms into new molecules, with consequent changes in the sum of all bond energies in the set of molecules that are matched by changes in kinetic energy.

Science Assessment

Item AP033006: Select a model that illustrates the energy changes when a hummingbird uses sucrose to get energy. Using the model, explain how energy flows into and out of the chemical reaction system.