Homework 1 Answer Key.docx - CHM 114 GENERAL CHEMISTRY I...

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CHM 114 GENERAL CHEMISTRY I FALL 2018 TAKE HOME ASSIGNMENT #1 Show work on calculations to get full credit. Keep track of sig figs. 100 points total 1. (10 points) Consider the following processes that are typical of owning/operating a spaceship. Which of these are chemical processes? Which are physical? Explain your answers: a. An asteroid smacks into your ship and dents the passenger door: Physical process. Denting a solid structure does not change its composition. b. Your space fuel combusts in the presence of pressurized oxygen: Chemical. Combustion of any kind is a chemical change. c. Dew that collected on your windows freezes as you enter orbit: Physical. The dew is water; when it freezes, it is still water – just solid water. d. The sandwich you left on the teleporter pad starts to decompose and turn green: Chemical. Decomposition is a complex array of chemical changes that break down the structures of organic materials, largely for the benefit of the bacteria doing that decomposition. e. Your unlucky chief engineer is dissolved by a stowaway alien’s acid drool: Chemical. The key word here is ‘acid’ – any acid-base reaction is inherently a chemical change.
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2. (10 points) Identify the following as either heterogenous mixtures, homogenous mixtures, or pure substances. a. Diamond Pure substance (diamond is all carbon) b. A bowl of Skittles Heterogenous mixture – Skittles clearly vary in color c. A bowl of only orange Skittles Homogenous mixture (unless you want to argue that the air between the skittles qualifies to make it heterogenous – a matter of interpretation!) d. Lemon juice Homogenous mixture. Lemon juice is mostly a mixture of organic compounds (largely acids) and water. e. Oil & Vinegar salad dressing Heterogenous mixture. Oil and vinegar naturally separate into phases, even after being stirred.
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