1. Chemistry 2 Assessment Review Use the “Class Set” copy to answer all questions. You are welcome to take notes or write down your answers. You may NOT use your notes on your test this time. 

2. INQF/PS2A – writing scientific explanations related to properties Which type of plastic is the “mystery” purple plastic? – the purple plastic is the same as the red (HDPE) How do you know? – same relevant properties (sinks in alc and alc/H2O, floats in H2O and saltH2O, color stays when creased) Connections to identification of “mystery”? – each property helps to match the purple plastic to the red sample (densities and crease) while other irrelevant data doesn’t differentiate the purple plastic from the green, blue and yellow samples (flexibility, hardness, reactions to acetone, heat and HCl).

3. PS2A – physical / chemical properties Why are the properties listed considered to be “identifiable” characteristics? – because it doesn’t matter how big the sample size is, the characteristic properties stay the same (density of HDPE is 0.95g/ml in big or small piece) How could you tell if the purple plastic would be dishwasher safe? – look at the results of the heat test – no rxn = can get hot without changing shape

4. SYSC – system inputs and outputs During what parts of the life cycle is energy an input? – all parts – energy is needed to mine and process raw materials, manufacture containers, transport them to and from useful life and end of life During what parts of the life cycle is waste an output? – all parts – waste is always produced in various amounts In what situation is waste an input? – from end of life back to manufacturing (recycle) and back to useful life (reuse) How would the life cycle be affected if the “useful life” stage was removed? – if there were no useful life for the containers, the manufacturers would have no reason to process, therefore not needing raw materials, and in turn not needing end of life choices

5. PS2B – mixtures vs. compounds Are the following materials a mixture, a compound or an element … how do you know? Purple “mystery” plastic – compound, because it is HDPE – chemical formula of C 2 H4 (two different elements chemically combined) Hydrochloric acid – compound, because it has a chemical formula of HCl (two different elements chemically combined) Saltwater – mixture, because it is salt (NaCl) physically stirred into water (H2O), and can be physically reversed by evaporating the water and leaving salt behind

6. INQD – investigation variables In the plastics lab, what were the variables? Manipulated – – types of plastic Responding – – properties (chemical and physical) Controlled – – types of tests, size of plastic pieces What would change if you had no controlled variables? – results would not be valid (for example, if the “types of tests” were not the same, how would you be able to compare the types of plastic?)