Inter-level Scaffolding and Sequences of Representational Activities in Teaching a Chemical System with Graphical Simulations

Abstract

Chemistry knowledge can be represented at macro-, micro- and symbolic levels, and learning a chemistry topic requires students to engage in multiple representational activities. This study focused on scaffolding for inter-level connection-making in learning chemistry knowledge with graphical simulations. We also tested whether different sequences of representational activities produced different student learning outcomes in learning a chemistry topic. A sample of 129 seventh graders participated in this study. In a simulation-based environment, participants completed three representational activities to learn several ideal gas law concepts. We conducted a 2 × 3 factorial design experiment. We compared two scaffolding conditions: (1) the inter-level scaffolding condition in which participants received inter-level questions and experienced the dynamic link function in the simulation-based environment and (2) the intra-level scaffolding condition in which participants received intra-level questions and did not experience the dynamic link function. We also compared three different sequences of representational activities: macro-symbolic-micro, micro-symbolic-macro and symbolic-micro-macro. For the scaffolding variable, we found that the inter-level scaffolding condition produced significantly better performance in both knowledge comprehension and application, compared to the intra-level scaffolding condition. For the sequence variable, we found that the macro-symbolic-micro sequence produced significantly better knowledge comprehension performance than the other two sequences; however, it did not benefit knowledge application performance. There was a trend that the treatment group who experienced inter-level scaffolding and the micro-symbolic-macro sequence achieved the best knowledge application performance.

Appendices

Appendix 1: Sample Questions/Tasks in the Three Representational Activities

Questions in the Macro Activity

• Slowly drag the fire holder to the bottom of the aerosol can, observe and describe what happens.

• Think about this: Why does the aerosol can explode as you move the fire close enough?

Questions/Tasks in the Symbolic Activity

• Slowly drag the temperature slider from left to right, record the values for temperature, pressure and volume for five times.

  

• Please put the data points you recorded in the following graph

  

• Discuss with your group partners: What do you learn from the data?

Sample Questions in the Micro Activity

• Please look at one molecule. Does it move in a certain direction or in random directions?

• How could a molecule keep changing directions?

• Please drag the temperature slider back and forth, describe how do the gas molecules behave and interact with each other?

Appendix 2: Pre- and Posttest

Pretest

1. An infected tooth forms a tiny space that fills with gas. The gas puts pressure on the nerve of the tooth, causing a toothache. Which of the following should the patient choose to relieve pain?

A. Moist heat

B. Ice pack

Why? Explain

2. Car tires are more likely to pop in the summer than in the winter. Please explain why that happens

Posttest

Comprehension subtest

1. Gas is composed of______________

2. Do gas molecules move in certain directions? How do gas molecules behave? How do gas molecules interact with each other?

3. Label the variables on the picture (In this labeling question, a snapshot of the simulation was given, and participants were expected to correctly label temperature, volume and pressure, and the three unit names for the variables)

4. You throw an aerosol can into the fire and it explodes. Please explain how that happens.

5. What is gas pressure? How do you understand gas pressure?

6. When the volume of a certain amount gas stays the same, the higher the temperature, the ______________ the gas pressure. How does that happen?

7. If you want to decrease gas pressure, what should you do? Why?

Application subtest (same as the pretest)

1. An infected tooth forms a tiny space that fills with gas. The gas puts pressure on the nerve of the tooth, causing a toothache. Which of the following should the patient choose to relieve pain?

A. Moist heat

B. Ice pack

Why? Explain.

2. Car tires are more likely to pop in the summer than in the winter. Please explain why that happens.

Appendix 3: Coding and Scoring Scheme and Coding and Scoring Examples (Open-Ended Questions)

Knowledge Units in the Coding Scheme

Functional Knowledge Units

F1:

Causal relationship between gas pressure and some macro-level phenomena, e.g., increased pressure caused the car tire to explode

F2:

Causal relationship between temperature and pressure, e.g., lower temperature leads to lower pressure

F3:

Causal relationship between temperature and speed of molecular movement, e.g., when temperature is higher, molecules move faster

F4:

Causal relationship between temperature and molecular collision rate, e.g., when temperature is higher, molecules bounce off more

F5:

Causal relationship between molecular behaviors and pressure as an emergent function, e.g., molecules bouncing off more causes pressure to increase

Behavior Knowledge Units

B1:

Random movement of gas molecules, e.g., molecules move in random directions, molecules move all over the place

B2:

Speed change of gas molecules, e.g., molecules move faster/slower

B3:

Bouncing behaviors of gas molecules, e.g., molecules collide with each other, and molecules bounce off container walls

Structural Knowledge Units

S1:

Mention “temperature” of gas without mentioning its relationship to gas pressure or molecular behaviors, e.g., it is about temperature

S2:

Mention “molecules” without describing their behaviors or interactions, e.g., because of molecules

Coding and scoring procedure In order to increase the objectivity in scoring participants’ answers, we reviewed each answer to an open-ended question for the presence and absence of each knowledge unit listed above. We applied the codes F1, F2, F3, F4, F5, B1, B2, B3, S1, S2 if the associated knowledge units were present. To score an answer, we assigned 1 point to each functional and behavior knowledge unit and assigned 0.5 point to each structural knowledge unit. If an answer did not contain any of the knowledge units in our list, no code was assigned and the answer was scored 0.

Sample question from the comprehension subtest: Do gas molecules move in certain directions? How do gas molecules behave? How do gas molecules interact with each other?	Sample question from the comprehension subtest: You throw an aerosol can into the fire and it explodes. Please explain how that happens	Sample question from the comprehension subtest: What is gas pressure? How do you understand gas pressure?	Sample question from the application subtest: Car tires are more likely to pop in the summer than in the winter. Please explain why that happens
Answer: “By behaving, I think” Code: none Score: 0	Answer: “It happens by the can burning up as the fire moves closer to the aerosol can” Code: none Score: 0	Answer: “Gas pressure is when you pressure the gas” Code: none Score: 0	Answer: “Because the sun makes it explode” Code: none Score: 0
Answer: “Bumping into each other” Code: B3 Score: 1	Answer: “Heat in the fire makes molecules in the can go crazy then end up exploding” Code: F3 Score: 1	Answer: “Gas pressure is made of molecules, I don’t know the rest” Code: S2 Score: 0.5	Answer: “They are more likely to pop in the summer because the heat of the sun would make the tire to get heated up and over inflate” Code: S1 Score: 0.5
Answer: “Gas molecules go random ways, gas molecules interact with each other by bumping into each other” Code: B1, B3 Score: 2	Answer: That happens because the more something heats up the faster the molecules move so they hit the walls of the soda cans so hard and much the can exploded Code: F3, F4 Score: 2	Answer: “Gas pressure is when the pressure in the air is heavy so the molecules movement are at full speed” Code: B2 Score: 1	Answer: “In the summer would pop the tires, because of the temperature, if it’s hot the pressure will rise” Code: F2 Score: 1
Answer: They move in random directions and they bounce off each other. They move fast and slow Code: B1, B3, B2 Score: 3	Answer: “The molecules create an impact by bumping into each other when in contact with heat, therefore creating pressure that the can can’t hold” Code: F3, F2, F5 Score: 3	Answer: “What I know about gas pressure is that if the temperature is high the molecules moved faster, the pressure controlled the molecules” Code: F2, S2 Score: 1.5	Answer: “Because of the molecules speeding and there is a lot of pressure on the tires so they pop” Code: B2, F1 Score: 2

Overall number and proportion of students who scored 0–0.5 (low-level understanding—LU), 1–1.5 (medium-level understanding—MU) and > 1.5 (high-level understanding—HU) for each item
LU	MU	HU	LU	MU	HU	LU	MU	HU	LU	MU	HU
N = 8 7 %	N = 36 29 %	N = 79 64 %	N = 64 52 %	N = 37 30 %	N = 22 18 %	N = 96 78 %	N = 27 22 %	N = 0 0 %	N = 69 56 %	N = 28 23 %	N = 26 21 %

1. Note To demonstrate how well students answered the open-ended questions in general, we selected four open-ended questions from the posttest and calculated the overall number and proportion of students who demonstrated low-level understanding, medium-level understanding and high-level understanding. In the results section, for statistical comparisons across the six conditions, we summed up the scores of all questions in the pre- and posttest for each student and compared group means of overall scores