Category Archives: B. T-GEM


One of the areas that I noticed my students struggling with when I taught science in the past was diffusion and osmosis.  There were a few ways I could tell this was a topic rife with misconceptions:

  1. They were concepts that most students struggled to define/explain adequately on tests.
  2. Even high performing students had trouble differentiating the two.
  3. Their hypotheses and reflections on labs showed a lack of understanding

I think one of the reasons is that they have difficulty with the scale that is involved and the concept of concentration gradients.  From a scale point of view, I think students have misconceptions about liquids because of their sensory observations.  They see liquids as homogenous substances, and struggle to understand that there are tiny atoms/molecules moving around and colliding.  With concentration gradients, I think they have a difficult time understanding why particles move from areas of high concentration to areas of low concentration.  Two prominent misconceptions I have noticed arise from some of the most popular ways of describing diffusion.  The first is the personification of particles – teachers often imbue consciousness on particles by describing diffusion in terms of particles ‘seeing’ the high concentration and ‘knowing’ that they must move to another place.  Another way of describing concentration gradients is the idea of a ‘downhill’ force that takes particles from high concentration to low concentration.  My students would often take this explanation and turn it into a misconception that diffusion was driven by gravity.

For the purposes of my T-GEM, I have ‘created’ a new tech tool –  an interactive demo/game in which particles move around the screen in a way consistent with kinetic molecular theory (please forgive my improvised attempt at showing this visually in my video!), and students can control the variables.  I think interacting with a demo/game like this would help dispel misconceptions and help students make meaning of the process.


T-GEM: Building Circuits

Last year I taught Grade 7 Science and one of the more difficult outcomes to teach was Electricity.  Many of the students know that electricity is there but since they cannot “see” it the struggled with the concepts.

These were the outcomes for the electricity unit:

  • Construct and draw a simple series circuit and a simple parallel circuit (P1)
  • Compare the characteristics of series and parallel circuits (P2)
  • Describe simple applications for series and parallel circuits (P3)

The following is a 3-step T-GEM cycle for Electricity :

Teacher Students

Teacher asks students to create a mind map around the word electricity.


Teacher listens while taking note of the misconceptions that they may possess.


In small groups students will generate a mind map, letting their ideas and words flow.


Students present their mind maps and hang them on the wall.



Teacher gives students a battery, wires, switch, and a light bulb. Ask students to form a complete circuit and try to light the bulb.


Teacher walks around observing how students are constructing the circuits

Students working together they try and conduct a circuit.




Teachers helps any groups that needs it and explains the difference between a series and a parallel circuit.



Students look at where they went wrong and modify accordingly.


I used the phet website (

This was an excellent resource to use during this unit because the resources at our school are few and far between and this really helped the students understand the concept of building circuits.

Staying Afloat – Sink and Float Density T-GEM

When considering a challenging science concept, I recalled struggling with explaining the concept of floatation, or “sink or float”, when teaching kindergarten. Although exploring objects that sink and float in water is highly intriguing for young students, the reasoning behind which objects sink and float can get complicated and too abstract for a student at that age to fully understand. Why does a tiny popcorn kernel sink and a large watermelon float?

In the BC’s New Science Curriculum, density is not specifically addressed until grade six when students investigate heterogenous mixtures. In Suat Unal’s (2008) research, he recognizes that elementary students possess significant misconceptions relating to floatation as evidenced through other research by Biddulph and Osborne (1984) and Gürdal and Macaroglu (1997). This other research finds that “students offered many unrelated factors such as mass and weight” to explain floatation activity, and that even after sink and float investigations and learning of Archimedes had been completed, students “were unable to construct scientific understanding” about sink and float relations (p.135).

In preparing a T-GEM lesson, I wanted to include student investigation of objects that sink and float in water, as well as in other liquids, to help student understanding of the concept of density. Because of this specification, the Gizmos simulation that is included in the following lesson is ideal, whereas other simulations that I found online provide investigation solely with water. An image of the simulation follows:




T-GEM Lesson – Density – Grade 6 (BC Curriculum)

Teaching Strategies Student Activity
Read Aloud – Chapter 5, “Archimedes and King Hiero’s Crown” from Archimedes and the Door of Science by Jeanne Bendick. Class discussion narrating ideas presented through reading; teacher comments neutrally

GEM – Cycle 1

G – Generate Instruct students to investigate selected object in a sink and float investigation using water in a container. Students are to record observations on a T-chart as well as represent observations on a paper chart template using cut and paste images of the selected objects. Ask students to make a prediction about the types of objects that sink vs. float. With a partner, students test sink and float tendencies of selected objects in water and record on a T-chart; Students place cut out pictures of objects onto chart template; After recording data, student journal predictions about the types of objects that sink vs. float.
E – Evaluate Ask students to record anything that does not make sense about their observations and prediction – questions they may have or confusing patterns; Ask students to think of a way to conduct a sink and float investigation that could help clarify some of the observations and predictions that do not make sense. Prompt students with a change in variable – either the solid objects or the liquid. Teacher guides student through extension investigations using an alternate liquid. Students discuss with partner and record observations and predictions that don’t makes sense; Share questions and confusing patterns with class and plan a new investigation with changing one variable. Watch teacher directed demonstration and participate in class discussion.
M- Modify Ask students to determine what changes they need to add to their T-chart and paper pictorial chart to accommodate the new information accessed from the teacher-led investigation Student makes adjustments to representations of t-chart and paper pictorial chart by including results with  variable change.

T-GEM – Cycle 2

G- Generate Direct students to Gizmos online simulations: {Teacher needs to previously set up an account and select simulation to add to their “class”.}

Lead students to the the elementary level lesson under Physics called “Density” Provide a short explanation of the activity, sharing that instructions are provided in text within the simulation. Remind students to record on a new chart the weight (g) of the object when measured on the scale, the volume displacement (mL)of the object within the graduated cylinder, and the the ability of the object to sink and float in each of the available liquids (water, oil, gasoline, sea water and corn syrup). After all objects have been tested, journal a relation statement based on the acquired data.   

In partners, students use the Density simulation measuring weight and volume displacement of the following objects: ping pong ball, golf ball, toy soldier, apple, chess piece, penny, egg, rock, gold nugget, crown 1 and crown 2. Students will test the floatation of each object in five different liquids and record their observations. Students will analyze their data and make a relation statement in their journal.
E-Evaluate Teacher provides students with the equation for density:

Density = Mass/Volume
And the density measurements for the 5 liquids within the simulation:

Water = 1.00 g/mL

Oil = 0.92 g/mL

Gasoline = 0.70 g/mL

Sea Water = 1.03 g/mL

Syrup = 1.33 g/mL
Ask student to evaluate their relation statement using this new information

Students compare the density of the measured objects using the density equation and with the density of the liquids and evaluate their relation statement making changes as necessary.
M-Modify Ask students to design a pictorial representation (model) of the data. Students can choose to represent objects that sink, or float, or both. The model should include density measurements of both the liquids and objects. The model should include a comparison of two or more liquids. Recommend using a chart or graph format with pictorial representations of objects. Students choose data to include in their model representation following criteria provided by teacher.




Bendick, J., (1995). Archimedes and the door of science. Bathgate ND: Bethlehem Books.
BC’s New Curriculum, (n.d.). Science 6. Retrieved from
ExploreLearning, (2017). Gizmos. Retrieved from
Khan, S. (2007). Model-based inquiries in chemistry. Science Education, 91(6), 877-905. Doi 10.1002/sce.2022
Unal, S.,(2008). Changing students misconceptions of floating and sinking using hands-on activities. Journal of Baltic Science Education, 7(3), 134-146. Retrieved from

T-GEM and Earth’s rotation


Challenging Concept:


The concept that I choose was one that my grade 4 class struggled with early on in the school year.  Understanding the lunar cycle, phases of the moon, along with the tilt of the earth’s axis and its impact on the various seasons was a challenge for them. I used various demonstrations with a globe, flashlight and pictures on the projector.  When they completed an extension activity afterwards, many of them still couldn’t explain how those things worked.


3 Step T-Gem cycle


  Discuss the moon and Earth’s gravity and rotation
Generate Demonstrate the rotation of the Earth using a model around the Sun.

Use a flashlight to shine on various parts of the and Earth to show where light would hit and various times of the year and day. Ask questions about where the students think it is cold/hot, daylight, nighttime

Evaluate Allow students to create their own diagrams of the Earth’s rotation and demonstrate how that impacts the various seasons.
Modify Ask students to consider their original ideas then consider how the various shapes of the moon are impacted by the rotation around the Earth

I found a website the models lunar phases and provides students with a few different vantage points with regards to positing on the moon and what that would look like on earth based on the different times and days of the year. You can see the sun rise and fall as the clock moves throughout the day, the moon’s position around the earth change, as well as the calendar year moving through each day.




The Atoms Family in Grade 3

“Us primary [kids] are much brighter than grown ups think! We hear about atoms all the time on the Big Bang Theory and The Simpsons, so why have they decided to keep atoms a secret in primary school?”Atomic Kids  (2013)

Well, the secret is no more in BC! I must admit, that last year when I started to explore the new curriculum I was astounded to find “all matter is made of particles” and “atoms are building blocks of matter” in grade 3 science (“Building Student Success,” 2016). I was also intimidated. Through a lot of exploration with my class I was blown away to see how captivated and interested they were in the subject. I created this visual to showcase how I would integrate T-GEM into my approach with this topic:

Atoms & Molecules with T-GEM by Allison Kostiuk

I found a PhET simulation lab for “Build an Atom” that I would utilize. Funny I did not realize I had found a “simulation lab” last year until I revisited it again through my class blog. I found that this resource helps my students “visualize aspects of science that are…too large [and] too small…to view” (Khan, 2010, p. 216).


Atomic Kids. (2013). Retrieved March 03, 2017, from

Building Student Success – BC’s New Curriculum. (2016). Retrieved March 03, 2017, from

Khan, S. (2010). New pedagogies for teaching with computer simulations. Journal of Science Education and Technology, 20(3), 215-232.


P.S. If you are looking for a cute song related to this topic, The Atoms Family is a great one!


T-GEM is a pedagogical approach used to design technology-enhanced, inquiry-based learning activities.  It’s primarily goal, as defined by its name, is have students “G”enerate ideas about scientific relationships, “E”valuate their constructed knowledge, and “M”odify this knowledge as they apply their knowledge to more complex problems that help refine their understanding. (Khan, 2007)

An area that may benefit from the addition of T-GEM instruction would be the Science 9 electricity unit that I teach.  In it, one of the learning outcomes is for students to understand the relationship between voltage, current, and resistance in both series and parallel circuits.  Traditionally, this may have been taught didactically through notes and post-lecture activities simply to reaffirm the lesson topics.

However, in recent years I have approached this from an inquiry-based perspective that has students building various circuits, measuring the three properties, and drawing conclusions.  I feel that this can be extended even further with the T-GEM approach.

Below is a flow chart of how I envision an “Electrici-T-GEM” would progress, as well as key points to guide student focus.

Links to simulations:

Sim #1

Sim #2

Sim #3



Khan, S. (2007). Model-based inquiries in chemistry. Science Education, 91(6), 877-905.

Evaporation – Where does that water go?

While the ideas behind Technology-enhanced Generate-Evaluate-Modify (T-GEM) were not new to me on their own, this particular model of thinking, leading to inquiry and ultimately a deeper understanding of concepts taught, was. I appreciated the step-by-step process by which GEM takes both educators and students through the learning process of generating, evaluating and modifying ideas; a model which I believe highlights a weakness in my own teaching of science and math. For me, one of the most important points to consider was the cyclical pattern in which GEM encourages students to create new hypotheses as they generate, examine, and evaluate new and existing data, and then re-examine and modify relationships between data and ideas/hypotheses generated (Khan 2007 & 2010). I believe I often struggle with time constraints (either real or perceived/self-imposed) which means that I miss important steps in this learning cycle. Going forward, I believe that having a model like T-GEM will help me focus my planning on creating a more inquiry-based environment in my own classroom. As highlighted by a survey item generated by Khan, students overwhelmingly felt that “having us generate, evaluate, and modify relationships in class is valuable for my understanding of the concepts” taught (in this case referring to chemistry) with 91% of students agreeing with the statement, 0% disagreeing, and 9% neutral (Khan, 2007, p.900 – included percentages; Khan, 2010, p. 227 – listed as a survey question only). While this particular survey question related to a university-based chemistry course, I believe it is true for any science-based concept that students are required to learn.

The simulations in Chemland were not applicable to my current students as I work in a grade 4/5 split class, but I enjoyed exploring the program and I recognize the incredible possibilities the simulations would provide for an appropriate age/grade group. Having said that, I could see the “Specific Heat Capacity” simulation ( and even “Heat Transfer Between Substances” ( having the potential to be used by at least some students in a higher-level intermediate grade within an elementary school (i.e., grade 6/7).

T-GEM Model with assignment (aimed at grade 4 Science):

For this activity, I chose to focus on evaporation due to the fact that students often have a variety of misconceptions related to “phase changes of water” (p. 4), as is identified by Laura Henriques (2000) in “Children’s misconceptions about weather: A review of the literature.” Henriques identifies that rather than understanding “water left in an open container evaporates changing from liquid to gas,” children may believe the water “is absorbed by the container” or simply “disappears (Bar, 1989; Osborne & Cosgrove, 1983);” that it “changes into air or disappears and turns into air ((Bar, 1989; Brody, 1993; Lee, et al., 1993; Osborne & Cosgrove, 1983);” or that “the water dries up – it is not steam, it just dries up and goes into the air (Bar, 1989)” (p. 5). Henriques points out that “all the misconceptions here (except water being absorbed by the container) are basically true since water vapor is a legitimate component of air,” however, students generally “were not viewing the evaporated water as a component of air because air to them is nothingness” (p. 5).

G – Generate:
To access prior knowledge, check for misconceptions, and generate ideas about the topic, evaporation, I would begin with a few different activities to activate thinking and knowledge from different angles.

1) First, students would complete a “What-So-What?” activity. Students would be given a handout with a t-chart on it. The left column of the chart says “What?” and the right column says “So What?” Students would be shown two pictures and would be expected to respond on “What” they see and why each thing they see might be of importance (“So What?”). The pictures will be projected through a projector/proxima to a screen for them. The first picture would be of a bowl/container filled with water, perhaps sitting near a window or outside on a sunny day. The students would be given a set amount of time (I usually allow only one minute) to list as many things as possible that they see in the picture. They are then given additional time (I usually give about two minutes) to respond to why each thing they saw might be important in the “So What?” column. Next, students would be presented with a picture of the same container, except this time it would be empty (time and weather could change, but container and its location would remain the same). They would repeat the “What-So-What?” process. I would then do a “Whip Around” to have each student share one idea they came up with from the pictures – students are allowed to expand on an idea already shared by a peer, but must make it “their own.”

2) Originally, I had thought that I would have students generate ideas they had about the term “evaporation” by doing an idea web on paper. However, having read Khan’s (2012), “A Hidden GEM: A pedagogical approach to using technology to teach global warming” I decided I would borrow an idea from Khan’s generate strategies and use the Cmap program discussed in the article. Cmap software was developed through research by the Florida Institute for Human & Machine Cognition (IHMC) and “empowers users to construct, navigate, share and criticize knowledge models represented as concept maps” (IHMC, 2014). It is marketed as a software that can be used by all age groups, as individuals, as well as within schools and institutions ( I had never used Cmap before, but found it very easy to download and to use at basic level. I feel that my grades 4/5 students would be comfortable using this application.

Using Cmap, I would ask students to create an initial map of ideas they can generate about their beliefs related to evaporation. This would likely include ideas they generated through the “What-So-What” activity, from the “Whip Around” activity, as well as from their own prior knowledge. I would allow students to work in partners to encourage discussion about evaporation and ideas generated. Students would create a basic Cmap at this point.
For example:

At this point, students would be asked (with their partner) to create a hypothesis based on the question: “What happens to water when it is left in an open container?”

(N.B. “What-So-What?” is a strategy I use quite often with my students, especially in Science and Social Studies lessons. I do not have an exact reference for this strategy, but it was shared by Faye Brownlie during a presentation she gave when visiting the district where I work a couple of years ago. The following is a link to her website:

E – Evaluate:
When I began searching for interactive simulations online, I found an interactive evaporation simulation that seemed to fit well with both the grade level I am aiming at (primarily grade 4) and the curriculum content that students will be expected to know “Solids, liquids and gases as matter” (B.C. Ministry of Education, 2016). Working in pairs to allow for discussion, students would use the online evaporation simulation to evaluate the ideas they generated in their Cmap. Students will be able to experiment with the following variables: how humid their environment will be (full sun, sun with clouds, clouds with rain), air temperature (between 10 and 40 degrees Celsius), and container shape (flatter and wider versus taller and thinner).
As students progress through the simulation, they will record/graph their findings taking into account the changes in variables.

Interactive evaporation simulation link:

M – Modify:
Once they have completed the interactive evaporation simulation and recorded their findings, students will return to their original Cmap webs to modify their original webs. New ideas/findings/knowledge can be added to the existing Cmap, and new concepts can be added. In addition to this, new connections can be made, connecting existing ideas together, and causal relationships can be identified, all within the Cmap.
If I am looking for a more in-depth assessment or for further evidence of learning, I could ask students to explain orally (conference-style) what they observed happening during the simulation and to explain the concepts and connections shown on their Cmap. I could also ask students to write a paragraph to explain what they have learned and/or to draw a picture showing their understanding. Once modifications to their Cmap are complete, students would be asked to modify their original hypothesis, based on the data they have collected (based again on the question: “What happens to water when it is left in an open container?”).


British Columbia Ministry of Education (2016). Area of learning: Science, grade 4. Retrieved from

Henriques, L. (2000, April). Children’s misconceptions about weather: A review of the literature. Paper presented at the annual meeting of the National Association of Research in Science Teaching, New Orleans, LA. Retrieved 7 January, 2017, from:

IHMC. (2014). Cmap. Retrieved from

Interactive evaporation simulation (n.d.). Retrieved 27 February, 2017, from

Khan, S. (2012). A Hidden GEM: A pedagogical approach to using technology to teach global warming. The Science Teacher, 79(8), 59-62.

Khan, S. (2010). New pedagogies for teaching with computer simulations. Journal of Science Education and Technology, 20(3), 215-232.

Khan, S. (2007). Model-based inquiries in chemistry. Science Education, 91(6), 877-890

T-GEM – Heating Curve of Water

GEM is an acronym for a pedagogical approach to teaching science that involves students taking an active part in constructing their own understanding of relationships and concepts, as well as learning how the scientific inquiry process works (Khan, 2007).

G in GEM stands for students Generating ideas about relationships,
E represents students Evaluating the relationships they have constructed,
M is the stage where students Modify those relationships to account for any discrepancies discovered during the modification stage, or to rectify any misconceptions held.
T-GEM is an adaption of the strategy to incorporate the integration of Technology into its implementation in the form of simulations or interactive models.


In her case study, Khan highlighted an important piece to the GEM cycle. Background content knowledge provided by the teacher at the beginning of the lesson is an important step to help students make some sense of the data they will be seeing in the experiments and simulations. This is essentially activating their schema or their prior knowledge in order for the students to build on their conceptual knowledge.  If the students don’t know what they are looking at, seeing relationships in the data becomes difficult (Khan, 2007).

Computer simulations that assist students’ visualization of scientific phenomena have been associated with gains in conceptual understanding among science students (Khan, 2010).  This corresponds directly with the TPCK pedagogy allowing teachers to integrate interactive science simulations for students enabling them to grasp somewhat “invisible” concepts.

Over many years of teaching the science of Heat Energy, every year the students have misconceptions around the process of boiling liquids, and in particular the boiling of water. These misconceptions appear to have their basis in the way students observe their world around them (Johnson, 1998; Collins & Gentner, 1987). Andersson  (as cited in Driver, Guesne & Tiberghien, 1985, pg 82) found that 40 percent of twelve year old students expect water to continue to heat up even after it has reached its boiling point. The students also thought that the amount of time that heat was applied would affect the temperature would continue to affect the boiling point. This is true for my own experience with this age group doing a heating curve of water experiment. As the students got older, the percentage of students with this misconception decreased but there was still a large percentage who continued to misunderstand the nature of boiling. Driver, Guesne & Tiberghien (1985, p.82) state the “children’s logic had led them to think that the time of boiling and energy supply could influence the boiling point of a pure liquid.” They argue that “much of the confusion arises from the child’s view that heat and temperature are the same” (p.82). Since children have this preconceived notion they associate the increase in temperature with a corresponding increase in heat.

In order to combat this misconception in my science classroom I would use the T-GEM method to provide some computer simulations that complement the physical experiment of boiling water in the classroom.

Heating Curve of Water Lesson Plan

  1. Provide an Anticipation Guide on Heat and Temperature for students to complete and to generate a class discussion. This should elicit misconceptions, if any, to be aware of as we progress through the lesson.
  2. Generate – Students are asked to present a hypothesis on what they predict will happen when they heat an ice cube in a beaker over a period of time. They should use their knowledge and understanding of particle movement in matter, and heat energy to explain their hypothesis.
  3. Students will then conduct the physical experiment using hot plates, beakers, ice cubes, thermometers, and timing devices. They will work in partners, one to observe the beaker and read the thermometer at 60 second intervals, and the other to record the data and time the intervals. This could also be recorded by video using a device for students to replay.
  4. At the completion of the experiment, the students will graph their data to show the heating curve and provide an explanation to fit their observations, and prove or disprove their hypothesis. This is generally where most of the students have difficulty understanding why the temperature plateaus as the water changes states from solid to liquid, and again from liquid to gas. They are usually surprised that the temperature does not continue to rise at a steady pace throughout the whole process. It is here that I feel the computer simulations will benefit the students as they will be able to see the particles moving in one, and they can rerun the computer simulation showing the boiling point to determine the cause of the plateau.
  5. Evaluate – Students will be introduced to the two computer simulations showing the heating curve of water. One simulation allows them to view the particle movement as they are heated up demonstrating the changes in state, and the other allows them to complete the boiling water experiment in a virtual situation where they can observe the changes as the time increases. This also generates a heating curve graph for the students to compare to their own graph. If the students videoed the experiment, they can generate comparisons between the computer simulation and their video observations.
  6. Modify – Given the new information from the computer simulations, students can compare their data with the computer generated data and come up with new hypotheses for the plateaus in temperature. Small group discussions would be held for students to compare data, understanding and hypotheses. Discussions will help determine if there is a need to repeat the experiment for better observations, or to design a different experiment to explain the data and scientific phenomena.
  7. After discussion and evaluation, students will write a conclusion for their experiment that allows for all the information generated through the physical experiment, as well as the computer simulations.
  8. Students can now take their observations and hypotheses and apply them to other pure liquids.

Hopefully this will allow the students to understand the concepts of heat energy and changing states of matter.


Driver, Guesne & Tiberghien. (1985). Children’s Ideas in Science. Open University Press.

Johnson, P. (1998). Children’s understanding of changes of state involving the gas state, Part 1: Boiling water and the particle theory. The International Journal of Science Education, 20(5), 567-583.

Khan, S. (2007). Model-based inquiries in chemistry. Science Education, 91(6), 877-905.

Khan, S. (2012). A Hidden GEM: A pedagogical approach to using technology to teach global warming. The Science Teacher, 79(8). This article was written about T-GEM with middle-schoolers.

Fournat, J. (n.d.). PCCL | INTERACTIVE PHYSICS SIMULATIONS |Physics and Chemistry by a Clear Learning : free interactive physics animations | online learning for sciences | School support with interactive flash animations for lessons and corrected exercises. Electricity, Mechanics, Waves, Optics, Chemistry, Nuclear Physics. For Upper School, Secondary School, High school, Middle School and Academy. Retrieved March 02, 2017, from

Conquering Mt. Gravitation

It had been over a month since I created a Prezi so off I went…

Physics teachers are invited to “Make a Copy” of my Google Doc for this endeavor. I have been doing this activity for many years, however, it was not exactly following the GEM format.  Consequently, I added a level of complexity that involved “discrepant information” which created an opportunity for students to test a new hypothesis relating Force to Separation Distance.  I also added a question at the end of this activity that provided a “new case” for students to contemplate.

Overall, I think the new version of my project is significantly more complex.  My concern is that Grade 11 students will fold like cheap tents, as the original version already caused many a headache for many a student. However, this new GEM-ized version, allows students to be uncomfortable and creative.  Finishing this activity will undoubtedly make them feel like they have conquered a mountain!

Should anyone have any additional scaffolding ideas, please shoot them my way. (I appreciate that you may need a physics background in order to do this, however.)

Free Falling with T-GEM

Free fall is discussed in the Projectile Motion unit in the Manitoba Grade 12 Physics Curriculum.  Rane (2015) states,”researchers have proved that free fall misconceptions are very common among the students” (p. 1).  Upon a literature review, Rane (2015) has also found that, “most of the students believe that…heavier objects fall faster than lighter ones” (p. 2).  Upon conducting analysis using a 15 item free fall diagnostic test, it was found that “…students [believed] heaver objects…take half the time [while others believed] lighter [objects]…move faster” (p. 6).  It is clear that the concept of free fall is challenging.  I have designed the following T-GEM lesson to assist students in understanding free fall and associated ideas like mass, acceleration, velocity, and velocity-time graphs.

Khan (2007) describes the GEM process as a “…cyclical pattern in which students [generate], [evaluate], and [modify] hypotheses…” (p. 877).

  1. Generate – students use a set of data or computer simulations to hypothesize relationships in the analyzed data.
  2. Evaluate – students use the identified relationships and test them out on a new case or example.
  3. Modify – students modify their original hypotheses and apply them to new cases.

Khan (2007) highlighted an important prerequisite to the GEM cycle.   It is important to have a small but important didactic lesson on introductory and background information that helps students make sense of the data in the first place.  If the students don’t know what they are looking at, seeing relationships in the data becomes difficult.

Free Fall Lesson

  1. Prerequisite Information – students are introduced to the Free Fall Tower gizmo by Explore Learning.  Students are given instruction on how to manipulate the gizmo and the data that can be collected from the gizmo.  They are given a brief review of the concepts of acceleration, velocity, and mass.  Graphs of velocity versus time are also reviewed for cases of acceleration and constant velocity.
  2. Generate – students are asked to determine if there are any relationships as they observe different objects free falling.  They are asked to manipulate their gizmo with air as the atmosphere in this part of the activity.  They are also asked to observe the graph section for trials.  Some objects appear to have constant velocity as they near the end of their fall. – The goal here is to generate a hypothesis that larger objects fall to the ground faster and to generate explanations for this observance.
  3. Evaluate – once students establish the relationship that larger objects fall to the ground faster – the students are asked to conduct similar manipulations, instead now with no air (vacuum) as the atmosphere.  They quickly ought to realize no matter which object combination they choose, all objects appear to fall at the same time, regardless of shape, size, or mass.  This is the discrepant event that will challenge their original hypotheses and force students to come up an adjustment to their original hypothesis.
  4. Modification – Students discuss the discrepant event and attempt to come up with new explanations for why all objects appear to fall at the same time.  Through discussion with the teacher’s guidance – students are helped to the conclusion that mass, size, shape have no impact on free fall as acceleration due to gravity affects all objects equally.  The issue of different objects falling at different times is because of their shape and air resistance when air is the atmosphere chosen.  Students apply their new explanations to in class experiments with real objects to further solidify the concept of free fall.


Khan, S. (2007). Model-based inquiries in chemistry. Science Education, 91(6), 877-905.

Rane, L. V. (2015). Investigating Student’s Conceptual Understanding of Free Fall Motion and Acceleration Due to Gravity. International Journal of Allied Practice, Research and Review, II(VI), 01-08.