Properties of Gases

Introduction

Have you ever wondered why a hot air balloon inflates when you fill it with hot air?  Or, why your bicycle tires seem more inflated during the summer than winter?  In this webquest, you will be able to explore the fascinating properties of gases to solve these mysteries!  

Gases have various properties that we can observe both with our senses and with instruments.  Three such properties are pressure, temperature and volume.  It has long been known that these three properties are related to each other.  By understanding these relationships, it is possible to explain why gases behave a particular way under different conditions. 

This Webquest allows you to develop a better understanding of the properties of gases using a computer simulation.  In particular, you should learn how changes in volume, temperature and pressure interact in a closed system.   

Task

After reflecting on what you already know about gases from experience with your partner, you will experiment with the simulation to develop a better understanding of how a gas’s temperature, volume and pressure interact in a closed system.  With this knowledge you and your partner should be able to answer several questions about the properties of gases and be able to make predicitions about real life scenarios.  You should e-mail your answers to the teacher when you are finished.  

Process and Resources

Step One.      Download and save this document to your computer: http://www.mediafire.com/?sv1x5vn2nhxxkci.

Step Two.      Answer the first question on the document:

                    

What do you know about the properties of gases?  For example, what happens when you heat a gas in a closed space?  Or, what happens to the pressure of the gas when you decrease the volume? Write as much as you know.

Step Three.    Skim through the information in the following links to familiarize yourself with the Ideal Gas Law:

Visual description: http://www.youtube.com/watch?v=WScwPIPqZa0

Written description: http://cnx.org/content/m12598/latest/

Step Four.      Run the gas simulation: http://phet.colorado.edu/en/simulation/gas-properties.  Answer questions 2 to 5 on the document.

Step Five.      E-mail your document to your teachers: marsh344@umn.edu and ytdl@hotmail.com.

Step Six.        Post your real-life example as a comment on this blog.  We will be using these examples in class at a later time. 

Evaluation

The evaluation is based on completion of the worksheet that you turn into the teacher. The following rubric pertains to the questions asked on the worksheet.

Question 1	Student answered the question and provided examples.	Student answered the question, but did not provide examples.	Student did not answer the question.
Question 2	Student correctly answered at least 80% of the table.	Student answered 50 to <80% of the table correctly.	Less than 50% of the table was answered correctly.
Question 3	All three of the graphs display proper relationships between the variables.	Two of the three graphs display proper relationships between variables.	One or none of the graphs display proper relationships between variables.
Question 4	Three or more of the scenarios had an accurate answer describing the phenomena.	Two of the scenarios had an accurate answer describing the phenomena.	One or none of the scenarios had an accurate answer describing the phenomena.
Question 5	A relevant example was provided by the student, and an accurate description of what variables were at play was given.	A relevant example was provided by the student, but no description was given.	Either an inaccurate example or no example at all was provided.

Conclusion

By completing this Webquest, you should have a better understanding of how a gas’s temperature, pressure and volume are related.  Furthermore, you should be able to use this understanding to explain what is happening in several real-life situations. 

Reflection on Model-based Learning

Model-based learning reinforces student learning because students are able to visualize the concepts they learn.  This feature is especially good when the concepts involve large-scale phenomenon like the greenhouse effect.  Such a concept would be difficult to develop an experiment or demonstration for, so the simulation provides an excellent alternative.  Furthermore, the simulation allows pupils to test different variables and see their effects on the relevant systems.  Regarding Webquest, I think it is a useful tool for both teachers and students.  Teachers can easily access good learning material that in turn supports their students’ learning.   

Greenhouse Effect Simulation

a.     Make general overview of the issue (corrections to your sketch?)

Light in the form of radiation is delivered from the sun to the Earth.  These light photons pass through the atmosphere, after which some are absorbed as energy by the Earth.  The infrared particles are not absorbed, but instead reflected back in all directions away from the Earth.  However, when the Earth’s atmosphere has greenhouse gases, these reflected infrared particles are again reflected back towards the Earth’s surface.  In this way, these particles become trapped between the Earth and its atmosphere, causing the planet to heat up.  It is important to note that when the Earth’s atmosphere contains no greenhouse gases, the infrared particles can escape and the Earth is not heated.

b.    Do you know enough about the atmosphere?

I have a basic understanding of what causes the Greenhouse Effect.  However, I do not understand some components of this process.  For example, why is it only that the infrared particles are reflected back?  Also, why can these particles enter the Earth, but not escape the atmosphere.  Therefore, I would need to learn more about this topic before teaching pupils.

c.     What are the main things affecting the phenomena:

Concentration of greenhouse gases
Types of gases that make up the atmosphere
Amount of photons from the sun
To some extent, amount of cloud cover

d.    Run the simulations at least when there are: gas concentration is none and lots, 1750, and today.  Report your observations.

When gas concentrations are low, the Earth’s temperature hovers around -20C.  As the concentration of gases increases, the temperature of Earth also increases.  Furthermore, at higher concentrations of gas, the temperature rises at a faster rate.  Finally, when the concentration of gas decreases, the temperature also drops to its original levels.   

Model-based Learning

What kind of models were mentioned and what are their roles in learning?

When considering learning, there are many different types of models.  First, there are the mental models.  Mental models are internal representations that are largely based on prior knowledge; these models influence how we understand and interpret certain phenomena.  Another type of model is the learners’ mental model.  This model begins with students’ prior knowledge; then, as they learn a new concept, this model is either challenged or reinforced.  If challenged, a learner will develop a new mental model which more closely aligns with scientist’s models.  One final type of model is the hypermodel.  As opposed to mental models, hypermodels are external representations that describe a scientific phenomenon; most often, these models are “computer models embedded in interactive curricula.”  Ultimately, it is this system of models and their interactions which are involved in the process of learning.