Heat is the measure of the internal energy of a substance, in which the process of increasing the internal energy is heating the substance, and the process of decreasing the internal temperature is cooling the substance. In order for heat energy to flow, a temperature gradient must exist. When energy flows between substances of different temperatures, heat has been transferred from the substance of higher temperature to the substance of lower temperature. Heat can be transferred between substances by the processes of convection, conduction, or radiation. Convection is the movement of heat within a fluid, such as air or water, conduction is the movement of heat between two solid objects through direct contact of the molecules, and radiation is the movement of heat through space via electromagnetic waves (Tillery, Enger, & Ross, 2008).
In exploring heat transfer I was tasked with testing materials which would inhibit or slow the transfer of heat energy via conduction by covering the top of coffee mugs filled with hot water and comparing the temperature difference from zero minutes to 30 minutes. Materials which are effective in slowing the transfer of heat are known as insulators. For this investigation I chose to use the common household items newspaper, a plastic lid, cotton cloth, and cardboard, each with a thickness of 3mm to ensure I was only testing the effectiveness of the material itself since varying thicknesses could affect the results. I also established a control mug with no material covering the top to use as a comparison. To counteract any heat loss through the mug as opposed to the tested materials, I first filled each mug with hot water and placed them in the microwave for one minute to heat the mugs then emptying them prior to filling each mug with 400mL of boiling water. The ambient temperature of the room was 26 degrees Celsius. A starting temperature of 92 degrees Celsius was recorded and each mug was covered with the different materials being tested verifying that there were no spaces between the mug and the material for heat to escape.
My hypothesis was that the plastic lid would be the most effective insulator as it is less porous than the other materials thereby increasing the likelihood of the heat remaining trapped in the coffee mug. Since heat propagates across a gradient from higher temperatures to lower temperatures the heat from the 92 degree Celsius water wants to flow in direction of the 26 degree Celsius air surrounding the mug.
Upon analyzing the results (see data table below), I rejected my hypothesis that the plastic lid would be the best insulator of the materials tested. The data shows that the cardboard was the most effective insulator resulting in a decrease of 24 degrees Celsius over the 30 minute period compared with a 27 degree Celsius decrease in temperature for the plastic lid. My reasoning is that the plastic is a solid material with a dense arrangement of molecules which allow for the easy conduction of heat evenly throughout the material. The cardboard however has spaces of air between the layers which do not allow the heat to transfer as easily as the air molecules in the spaces are less dense making it difficult for the heat to transfer across the material. By comparison, the control mug with no material decreased 38 degrees Celsius allowing the heat to flow freely from the mug into the surrounding air. Overall, there was only a difference of 4 degrees Celsius between all of the materials used.
Perhaps letting the experiment run for an hour would produce a greater disparity between results of the materials thereby making the findings more conclusive. The temperature difference between the control mug and the other mugs with insulators becomes quite evident demonstrating that any material will retard the transfer of heat to some degree; however some materials are more effective than others.
Another variation for this experiment would be to use heated solids as opposed to liquids such as pancakes. Pancakes notoriously lose their heat quickly and an interesting investigation may be to see which materials are able to keep a pancake the hottest over a period of 30 minutes. An initial pancake temperature can be recorded then wrap each pancake with a different material and record a final temperature at the end of 30 minutes. I would expect any material with air pockets embedded in it would be the most effective, and those materials too porous or too solid would create a larger heat gradient for the transfer of the heat energy.
The most challenging thing for me during this investigation was ensuring all of my variables were as controlled as possible so as any temperature difference could be accounted for as a result of the material being used and not an outside factor such as heat loss through the mug, or varying thicknesses of the materials.
In conducting heat transfer experiments in my classroom using a structured inquiry format, students use three Styrofoam cups starting with different temperatures of water. One is the control using room temperature water, the second is ice water, and the third is boiling water. Students record the temperature of each cup every five minutes for an hour. After recording their data, the students create a triple line graph of their data, and they should find that the control cup does not change, the ice water cup should increase, and the boiling water should decrease. When the students analyze the graph they should come to the conclusion that if we were to extend the experiment over several hours or days, that the temperature of all three cups should be the same temperature of the air surrounding the cups due to heat wanting to reach a point of equilibrium between substances.
Temperature experiments are excellent activities in getting students to understand the concept of heat transfer as measurements can be easily recorded and results are fairly clear. These experiments also help reinforce the scientific process in making good observations, recording data, and drawing inferences and conclusions based on the results they achieve. Students have a common misconception that colder substances permeate hotter substances such as when they hold an ice cube in their hands, many will note that the cold from the ice goes into their hands making them feel colder. After conducting these experiments, the students are able to realize that no matter how heat is transferred, it will always flow from a region of higher temperature to a region of lower temperature.
Data Table
Material Temp 0 mins (oC) Temp 30 mins (oC) Temp Difference (oC)
Control (no material) 92 54 -38
Newspaper 3mm 92 67 -25
Plastic lid 3mm 92 65 -27
Cotton cloth 3mm 92 66 -26
Cardboard 3mm 92 68 -24
Ambient temperature surrounding the mugs is 26 oC.
Saturday, May 29, 2010
Sunday, May 16, 2010
Mass, Speed, and Momentum: Using Guided Inquiry in the Classroom
The type of inquiry used in the classroom is determined by the amount of information the teacher provides to the students. In using a guided inquiry format, the teacher simply provides the students with a research question, and it is up to the students to determine the method of testing and drawing conclusions from the results of the data collected (Banchi and Bell, 2008). For example, I had the opportunity to conduct a guided inquiry investigation being provided on the the question "How does the steepness of a slope and mass affect a collision outcome?"
I realized I needed to set up a model to demonstrate a scenario in which an object on variable slopes could collide with another object at the bottom of the slope. I decided to use a small toy truck (8 grams), a 27 cc wooden block (5 grams), a cardboard ramp (27.5 cm), three books, a meter stick, and a calculator. I also wanted to determine if the amount of mass could influence the collision outcome so I used a large bolt (12 grams) that could be added to the toy truck. I set up the model with one end of the ramp resting on a book, then simulate the collision by releasing the toy truck from the top of ramp and impacting the wood block on the floor at the base of the ramp. I then measured the distance the block traveled after the collision with the truck five times and calculated the average. I repeated this with ramp at a height of 3 cm, 6 cm, and 9 cm. I then duplicated that process with the 12 g mass attached to the truck and recorded the data from those trials to determine if the amount of mass made a difference in the distance.
Once I determined how I was going to test the research question, I needed to form a hypothesis. My hypothesis is that as the ramp height increases, the distance the block is moved will also increase. Secondly, the added mass will also increase the distance when compared with the data from the toy truck alone. The increase in distance will be a result of the increased speed the truck is able to generate as the ramp height increases thereby impacting the block with a greater force. Subsequently the added mass will provide the truck with more momentum thereby increasing the distance of the block after impact.
The results of the investigation confirm my hypothesis as the data shows that the average distance of the block increased from 16.4cm to 31.8cm as the ramp height increased from 3cm to 9cm for the toy truck alone with a mass of 8g. Similar results were achieved when an additional 12g of mass were added as the distance of the block increased from 26.4cm to 46.6cm when the ramp height increased from 3cm to 9cm. When displayed in a graph, the disparity between the averages in distance at each ramp height comparing truck only and added mass becomes more evident in this visual representation. This leads me to conclude that increasing the height of the ramp and added mass increases the speed of the truck thereby increasing the amount of force at impact due to the added momentum. Since momentum is directly affected by the mass and speed of an object, the evidence from the investigation confirms that claim (Tillery, Enger, and Ross, 2008, p 43).
In conducting this guided inquiry investigation I had to be very careful about setting up my testing model appropriately in order to achieve quantifiable results that would either confirm or reject my hypothesis. In keeping with the engineering design process model I realized the need, brainstormed different design options, selected a design, planned the investigation, created the model, then made necessary improvements along the way (TEACH, 2010). This type of inquiry allows freedom of creativity in constructing a testing model according to my own ideas, and not necessarily the ideas or guidelines imposed by someone else. I actually use this very same investigation in my classroom when studying Newton’s second law of motion as a structured inquiry lesson. The investigation I conducted above is divided into two separate investigations with the first altering the height of the ramp to impact an object, and the second using a fixed ramp height with additional mass added to the vehicle. In both instances, the students are able to determine that the force of the vehicle (momentum) increases as the speed and mass are increased. The students really enjoy both of these investigations as the real world implications are limitless. Relating this to any object that is moving will apply and further reinforce the concept of mass and speed determining the momentum of an object.
I like the concept of using this as a guided inquiry lesson, however many of my students come to fifth grade lacking fluency in the scientific processes necessary to carry out an investigation such as this. For this reason I use structured inquiry in conducting a complex investigation like this one due to the fact there are numerous variables which could affect the outcome thereby rendering the data collected insignificant for achieving the level of understanding of the content. With a significant amount of guidance and intervention as they develop their tests, however, the students should be able to successfully work through the investigation to achieve the desired results.
Guided inquiry allows the students freedom of creativity in designing and carrying out an investigation to find answers to a question provided by the teacher. The teacher’s role during the process is one of support, intervention, and frequent questioning in order to ensure scientific integrity in extending the students thinking and application of the scientific process. It is important to keep in mind however, that the experiment is a product of the students’ knowledge, and too much intervention would then become a product of the teacher. Students need to experience science to truly understand science, and balancing creativity with guidance through the guided inquiry process allows them to do just that.
References:
Banchi, H., & Bell, R. (2008). The many levels of inquiry. Science & Children, 46(2), 26–29.
TEACH Engineering: The Engineering Design Process: Retrieved May 16, 2010 from http://www.teachengineering.org/engrdesignprocess.php
Tillery, B., Enger, E., & Ross. F. (2008). Integrated science (4th ed.). New York: McGraw-Hill.
I realized I needed to set up a model to demonstrate a scenario in which an object on variable slopes could collide with another object at the bottom of the slope. I decided to use a small toy truck (8 grams), a 27 cc wooden block (5 grams), a cardboard ramp (27.5 cm), three books, a meter stick, and a calculator. I also wanted to determine if the amount of mass could influence the collision outcome so I used a large bolt (12 grams) that could be added to the toy truck. I set up the model with one end of the ramp resting on a book, then simulate the collision by releasing the toy truck from the top of ramp and impacting the wood block on the floor at the base of the ramp. I then measured the distance the block traveled after the collision with the truck five times and calculated the average. I repeated this with ramp at a height of 3 cm, 6 cm, and 9 cm. I then duplicated that process with the 12 g mass attached to the truck and recorded the data from those trials to determine if the amount of mass made a difference in the distance.
Once I determined how I was going to test the research question, I needed to form a hypothesis. My hypothesis is that as the ramp height increases, the distance the block is moved will also increase. Secondly, the added mass will also increase the distance when compared with the data from the toy truck alone. The increase in distance will be a result of the increased speed the truck is able to generate as the ramp height increases thereby impacting the block with a greater force. Subsequently the added mass will provide the truck with more momentum thereby increasing the distance of the block after impact.
The results of the investigation confirm my hypothesis as the data shows that the average distance of the block increased from 16.4cm to 31.8cm as the ramp height increased from 3cm to 9cm for the toy truck alone with a mass of 8g. Similar results were achieved when an additional 12g of mass were added as the distance of the block increased from 26.4cm to 46.6cm when the ramp height increased from 3cm to 9cm. When displayed in a graph, the disparity between the averages in distance at each ramp height comparing truck only and added mass becomes more evident in this visual representation. This leads me to conclude that increasing the height of the ramp and added mass increases the speed of the truck thereby increasing the amount of force at impact due to the added momentum. Since momentum is directly affected by the mass and speed of an object, the evidence from the investigation confirms that claim (Tillery, Enger, and Ross, 2008, p 43).
In conducting this guided inquiry investigation I had to be very careful about setting up my testing model appropriately in order to achieve quantifiable results that would either confirm or reject my hypothesis. In keeping with the engineering design process model I realized the need, brainstormed different design options, selected a design, planned the investigation, created the model, then made necessary improvements along the way (TEACH, 2010). This type of inquiry allows freedom of creativity in constructing a testing model according to my own ideas, and not necessarily the ideas or guidelines imposed by someone else. I actually use this very same investigation in my classroom when studying Newton’s second law of motion as a structured inquiry lesson. The investigation I conducted above is divided into two separate investigations with the first altering the height of the ramp to impact an object, and the second using a fixed ramp height with additional mass added to the vehicle. In both instances, the students are able to determine that the force of the vehicle (momentum) increases as the speed and mass are increased. The students really enjoy both of these investigations as the real world implications are limitless. Relating this to any object that is moving will apply and further reinforce the concept of mass and speed determining the momentum of an object.
I like the concept of using this as a guided inquiry lesson, however many of my students come to fifth grade lacking fluency in the scientific processes necessary to carry out an investigation such as this. For this reason I use structured inquiry in conducting a complex investigation like this one due to the fact there are numerous variables which could affect the outcome thereby rendering the data collected insignificant for achieving the level of understanding of the content. With a significant amount of guidance and intervention as they develop their tests, however, the students should be able to successfully work through the investigation to achieve the desired results.
Guided inquiry allows the students freedom of creativity in designing and carrying out an investigation to find answers to a question provided by the teacher. The teacher’s role during the process is one of support, intervention, and frequent questioning in order to ensure scientific integrity in extending the students thinking and application of the scientific process. It is important to keep in mind however, that the experiment is a product of the students’ knowledge, and too much intervention would then become a product of the teacher. Students need to experience science to truly understand science, and balancing creativity with guidance through the guided inquiry process allows them to do just that.
References:
Banchi, H., & Bell, R. (2008). The many levels of inquiry. Science & Children, 46(2), 26–29.
TEACH Engineering: The Engineering Design Process: Retrieved May 16, 2010 from http://www.teachengineering.org/engrdesignprocess.php
Tillery, B., Enger, E., & Ross. F. (2008). Integrated science (4th ed.). New York: McGraw-Hill.
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