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CHEM151_Lab_02 - GenChem Week 2 Today's Agenda Develop the...

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GenChem Week 2 Measurement and Identification Today’s Agenda: Develop the day’s problem. Perform first challenge: measure density. Discuss reporting measurements and significant figures. Perform second challenge: determine densities of known plastics. Develop a consensus on the correct values. Perform third challenge: identify unknown plastics. Discuss writing the report.
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GenChem One of the central goals of Chemistry is to analyze chemical substances. Detection: Does the sample contain substance X? Identification: What is the identity of the substance in this sample? Central Goals and Questions Separation: How can the substances present in the sample be separated? Quantitation: How much of substance X is in the sample? How do we do it?
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GenChem Imagine that you are interested in recycling plastics. For that purpose, you need to devise a procedure to separate mixtures with various types of plastics. How do you propose to do it? The separation needs to be based on the identification of a property that differentiates one type of plastic from another ( differentiating characteristic )
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GenChem In your groups: Analyze each of the plastic samples. Make a list of properties that differentiate one type of plastic from another. Identify those properties that depend on the size of the sample ( extensive ) from those that are not expected to vary with sample size ( intensive ). Select “the property” that you think is the best to differentiate and separate one plastic from another. Let s think!
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GenChem Density is an intensive property that is commonly used to differentiate and separate plastics during recycling. What do you need to measure to determine the density of each of the plastic pieces? Density is a measure of the mass of material per unit volume: ρ = m/V (mass and volume are extensive properties)
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GenChem First Challenge Determine the density of a piece of plastic using the tools available in the lab. Let s explore! Available resources: Available resources: Piece of unknown plastic. Piece of unknown plastic. Balances (TC 4). Balances (TC 4). Rulers, Rulers, vernier vernier calipers. calipers. Glassware. Glassware. Design a feasible procedure and implement it! You have 20 minutes
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GenChem Once you have found the density of your assigned plastic, report the value on the board.
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