Observations

Description

Observations Lab – Adapted for Virtual Lab Summer 2020 So much of science is observing a phenomenon, and then trying to figure out how and why it happened. Your introduction to chemistry begins by you making observations from a chemical reaction. The reaction involves the following chemicals: sodium bicarbonate (NaHCO3), calcium chloride (CaCl2), and phenol red (solution with water). Sodium bicarbonate is commonly known as baking soda. It is used in baking and is a common antacid. Calcium chloride is used to melt ice on sidewalks and is medically useful in replacing electrolytes. Phenol red is used in the diagnostic tests of renal (kidney) functions. You will use a mixture of phenol red dissolved in water. When these three chemicals are mixed together, what do you observe? Pre-lab • Describe a process that you might use to figure out how something happened? Give an example. For example, what you might you do if you start to notice your houseplant is dying. • Draw a picture of a graduated cylinder. • Describe the difference between de-ionized water and tap water. Data and Observations In a regular lab setting, you would use the following equipment to perform the experiment: sodium bicarbonate, calcium chloride, 0.04% solution of phenol red, deionized water, large and small bags, a 10.0 mL graduated cylinder, and two spoons. In place of performing the experiment, watch the following video to see the reaction. https://youtu.be/EGsJLy6KlMc The following procedure was followed in the video. One spoonful of sodium bicarbonate (NaHCO3) was placed in one corner of the bag. Two spoonfuls of calcium chloride (CaCl2) were placed in the other corner of the same bag. The two solids were mixed inside the bag. A volume of 10.0 mL of 0.04% phenol red solution was measured in a graduated cylinder and poured into a small bag. The small bag was placed inside the larger bag. The contents inside the bags were mixed together. Make initial observations about texture of solids, and any changes during the experiment. Questions and Tests 1. Which of the major changes you observed after the contents of the bag were mixed did you find most interesting? Write a question about that change that you can then answer through additional tests using some combination of the same materials Page 1 of 3 CHM110 SU2020 as in the initial experiment. (avoid “what would happen if” questions since there really is no plan involved in answering those questions) 2. Design and record a new procedure to answer the question you posed. Consider how you might alter the three variables: NaHCO3, CaCl2, and phenol red (mixed with water). You won’t run this experiment but think about how you might if you were in the lab. The same materials are available to you. 3. Propose a hypothesis (a tentative explanation) or make a prediction based your question on your initial observations, 4. Differing mixtures of the variables were run. Choose the result that matches your new procedure and question. Each result is a short video. Record your second set of observations about the result. 1. Baking Soda, Calcium Chloride and water: https://youtu.be/pdnj6ydStt8 2. Baking Soda and Phenol Red: https://youtu.be/QCURlzH_mO8 3. Calcium Chloride and Phenol Red: https://youtu.be/0EOPOGj8WvA 4. Baking Soda and Water: https://youtu.be/XlUIP9B_L-M 5. Calcium Chloride and Water: https://youtu.be/auIJunSmLO4 Report: To be submitted via Blackboard assignments. Part I. Claims and Evidence 1. Write an argument, and answer your question with a claim and provide at least 2 pieces of direct observational evidence to support your claim. **Need help with writing an argument? A document called “Using the CER argument style” is provided to you in your lab folder.** 2. What is one additional question you have that arose as a result of this investigation? Part II. Reflection Look at the following model: Harwood’s activity model (next page) 1. Indicate which components of the model you engaged in and in what order. 2. Provide a description of a scientific process (You may use your textbook) 3. Explain how the Harwood activity model is similar to and differs from what you know as “the scientific method.” ***the following format is preferred by my instructor**** How to write an argument using Claim, Evidence, Reasoning (CER) Definitions Claim: A statement or conclusion that answers the original question or problem. Evidence: Scientific data that supports the claim. The data need to be appropriate, sufficient, and free of inference to support the claim. Evidence does not include generalizations and beliefs about the data. Reasoning: A justification that connects the evidence to the claim. It shows why the data count as evidence by using appropriate and sufficient scientific principles. *Rebuttal: A description of alternate explanations which provides counter evidence and reasoning why the alternate explanation is not the most appropriate explanation for the question or problem. After completing the laboratory investigation and analyzing the data, answer the question or problem posed at the beginning of the investigation (claim). Determine what data from the experiment support the claim. Do not simply state the data support the claim but write several sentences with specific, appropriate and sufficient data – the actual numbers or observations from the experiment. Then, using appropriate and sufficient scientific principles, explain why the evidence supports the claim. If you have more than one question to answer (and thus claim to make), be sure to include evidence and reasoning for each claim. * A rebuttal is another valuable component to an argument, but will not be required in lab reports. Example Samples of butanoic acid and butanol were tested then mixed together and heated. After heating, two separate layers formed and each of these layers were tested. The results are tabulated below. Question: Does a chemical reaction take place when butanoic acid and butanol are mixed? Measurements Melting Point Volume Solubility in Water Density Before mixing and heating Butanoic acid -7.9oC 2.00 mL soluble 0.96 g/mL Butanol -89.8oC 2.00 mL Soluble 0.81 g/mL After mixing and heating Layer A -91.5oC 3.60 mL Insoluble 0.87 g/mL Layer B 0.0oC 0.40 mL soluble 1.00 g/mL Adapted from McNeil, K.L. and Krajcik, J.S., Supporting Grade 5-8 Students in Constructing Explanations in Science, Pearson, 2012. A chemical reaction did occur when butanoic acid and butanol were mixed and heated. The intensive properties of melting point, -7.9oC and -89.5oC, solubility in water (both soluble) and density (0.96 g.mL and 0.81 g.mL), of the starting materials differ from those of the products; layers A and B after heating. Layer A had a melting point of -91.5oC, was insoluble in water and had a density of 0.87 g/mL, which do not match any of the properties of the reactants. Layer B, while soluble in water like the reactants, has a different melting point, 0.0oC, and density, 1.00 g/mL, which are both higher than either reactant. During a chemical reaction, new substances with different chemical compositions are produced. The intensive properties, properties that are independent of sample size, of the layers after mixing and heating differ from those of the reactants indicating new substances were produced and therefore a chemical reaction had to take place