Chem Lab Mixtures Essay - Free Essays, Term Papers.
Materials: test tube, naphthalene, thermometer, hot water, burner, stand, clamp. Be careful as naphthalene vapour is poisonous: you can wear a breathing mask to reduce the risk of you inhaling the vapour Method. Fill a test tube with naphthalene until it is about a quarter full; Place the test tube in hot water to allow the naphthalene to melt.Cooling curves are the opposite. They show how the temperature changes as a substance is cooled down. Just like heating curves, cooling curves have horizontal flat parts where the state changes from gas to liquid, or from liquid to solid. You are likely to have used salol or stearic acid in a school practical lesson to make your own cooling curve.Naphthalene is a white, volatile, solid polycyclic hydrocarbon with a strong mothball odor. Naphthalene is obtained from either coal tar or petroleum distillation and is primarily used to manufacture phthalic anhydride, but is also used in moth repellents.Exposure to naphthalene is associated with hemolytic anemia, damage to the liver and neurological system, cataracts and retinal hemorrhage.
If you graph the heat added to a system versus the system’s temperature, the graph usually slopes upward; adding heat increases temperature. However, the graph levels out during phase changes, because on a molecular level, making a substance change state requires energy. After all the material has changed state, the temperature can rise again.What are Heating and Cooling Curves. What happens when you let a cup of ice sit out on the counter for several minutes? It melts, of course! The increase in temperature causes the water to change.
A cooling curve of naphthalene from liquid to solid. A cooling curve is a line graph that represents the change of phase of matter, typically from a gas to a solid or a liquid to a solid. The independent variable (X-axis) is time and the dependent variable (Y-axis) is temperature. Below is an example of a cooling curve used in castings.
