2. Look up the definition of a chemical change in your text and as a group write a paraphrase of the definition here:

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1 RUN TIME: 50 MIN LAB REPORT REQUIRED PL04 Page 1 of 5 POGIL LAB EXERCISE 04 Practicing the Skills of Observation and Experimentation on a Burning Candle Each member should assume his or her role at this time. The new manager takes charge of the POGIL folder and hands out the GRF and RRF to the appropriate members. The new recorder should record the names of the group members on the new GRF. Table 1. Group Member Role Assignments GROUP TYPE -> GROUPS OF THREE GROUPS OF FOUR MEMBER NO. -> Manager + + Reporter + + Recorder + + Reflector + + Technician + + Encourager + + SFUC + * + * OBSERVATION I: Observations are going to be very important throughout all of the experiments you will be performing in this class but is the primary process used in the successful completion of this lab. When you observe something, you are utilizing your senses: sight, touch, taste, hearing, and smell. Though you will not be using your sense of taste in chemistry labs, you will use the remaining senses throughout the experiments to come. Searching the literature concerning the topic of a hypothesis is a way of learning what others have found and is considered a necessary observation stage before any experiment. You will begin part of the literature search now by processing Items 1-3 below. Matter is changed by two types of processes: 1) a chemical change(s) and/or 2) a physical change(s). 1. Look up the definition of a physical change in your text and as a group write a paraphrase of the definition here: 2. Look up the definition of a chemical change in your text and as a group write a paraphrase of the definition here: + 5 MIN

2 RUN TIME: 50 MIN LAB REPORT REQUIRED PL04 Page 2 of 5 3. Come to a consensus answer to this question: What is the difference between a physical and a chemical change? Submit your responses to the instructor for validation before continuing. OBSERVATION II: The hypothesis for this experiment is that the physical and chemical processes required in the lighting and burning of a candle can be fully described by direct observation, measurement of mass and the conduction of a simple experiment designed to detect the production of a product(s) and/or the limitation of a reactant. You should have already begun the process by reading the assigned material of the webpage cites in the schedule. You have continued the process by the reading and processing of Observations I and II. The final step will be an introductory lecture/discussion on reaction basics, combustion, and the process of lighting and burning the candle will be described with clues as to the observations that are required to substantiate the hypothesis. STOP. Reporters should let the instructor know when you reach this point. OBSERVATION III: Lecture/Discussion Take detailed notes on handout! When the lecture is over begin processing Observation IV. OBSERVATION IV: The object of the next step is to gather information through detailed observation and collecting data that will experimentally demonstrate the mechanism of the burning of the candle. This step involves the observation of a burning candle setting on a digital, analytical balance (a balance capable of weighing to the nearest milligram or smaller). 5. At the direction of the instructor, members of the group should move to a weighing station. The instructor will zero the balance, place the candle on the balance and announce the candle s initial mass. The moment the instructor lights the candle all members of the group should begin to note their observations in Table 2 until 10 observations are made. Managers and reflectors are responsible for keeping this observation time to exactly five minutes. The recorder should also note the mass at end of every minute of observation MIN

3 RUN TIME: 50 MIN LAB REPORT REQUIRED PL04 Page 3 of 5 6. When time is up, return to your table and share your observations with your group. Modify Table 2 so that all unique observations are listed on each member s table. Finally, as a group, decide whether each observation appears to be evidence of a chemical or physical change. Table 2. List and Classification of Observations of a Burning Candle. OBSERVATION 1. Starting mass of candle: Ending mass of candle: 1 min: 2 min: 3 min: 4 min: 5 min: Net mass change 5 min: Average Mass loss: g/min 2. Phys. Chng. Chem. Chng. Reason for Classification Recorders should have the instructor examine your responses in Table 6. Before continuing MIN

4 RUN TIME: 50 MIN LAB REPORT REQUIRED PL04 Page 4 of 5 5. Using the information gained in Observations I-IV and related processing items, design an experiment you could do in five minutes with equipment from your lab kits that would help substantiate a hypothesis that burning a candle involves combustion as well as several physical changes. (Look in your lab manual for possible equipment you could use.) Write the experimental protocol on the back and share it with your instructor. Managers, call the instructor to your table to check and discuss your experiment. 6. Upon instructor approval, carry out your experiment. 7. As a group summarize the results of your experiment and what it indicated. EXERCISE END. All students should retain their copy of the lab. The manager should collect the GRF and the RRF, paperclip them together and place them in the left pocket of the folder. At home, please read the next page concerning the lab report that goes with this lab MIN

5 RUN TIME: 50 MIN LAB REPORT REQUIRED PL04 Page 5 of 5 THE FIRST LAB REPORT (10 Points). Each member of the group should submit a lab report based on the results from this lab. Please access the course website for format of the lab report as well as an example of an excellent student lab report. The format requirement is absolute. As can be observed from the course website, the lab report can be written in four or five sections. I recommend that you use the following four sections: Introduction, Materials and Methods, and the final section, Results and Conclusions. Introduction: This section should include the hypothesis as well as all the information necessary to understand how the hypothesis can be tested. The hypothesis of this experiment can be stated as follows: The hypothesis for this experiment is that the physical and chemical processes required in the lighting and burning of a candle can be fully described by direct observation, measurement of mass and the conduction of a simple experiment designed to detect the production of a product(s) and/or the limitation of a reactant. Specifically, the introduction should include at least the following discussion points: 1. Discussion of what constitutes a physical change with literature reference. 2. Discussion of what constitutes a chemical change with literature reference. 3. Discussion of how a candle burns with literature reference. (I suggest that you use as a primary source this website: 4. Discussion of what constitutes burning (combustion) including a chemical equation for the process as it occurs in a burning candle with literature reference. Materials and Methods: Describes the materials and procedures used in the experiment especially the experiment your group conducted. This should be a narrative not a list. Results and Conclusions: A summary of the results in an easily read and understood format. Any observation that would confirm the description of the mechanism of the burning of the candle as explained in the literature should be shown including the fact that reaction proceeds in a linear manner. The two major types of presentations are tables and figures (usually graphs). These devices are numbered and titled as shown in the format and example documents on the course website. They must be referred to directly in the text by type and number. For example: Table 1 describes the observations judged as evidence of physical change. Each set of results should address points made in the discussion and be related to supporting or denying the hypothesis. There should be a final summary sentence either at the beginning or end telling whether you think overall the results confirm or deny the hypothesis. The report will be due at the beginning of the next lab period.