ILC chemestry chapter 11
74. b) Select one example of a physical change from your table, and explain why it has a physical change.
Step number one where “A coarse screen made of metal bars filters large particles and trash, such as bottles and cans.” This would be considered a physical change because there is no chemical process taking place. As well you are able to see a physical change in the water due to trash and debris being filtered out by nothing more then a screen. This screen is doing nothing more other then stopping trash larger then its bars pass through. Thus, making it a physical change.
74. c) Select one example of a chemical change from your table, and explain why it is a chemical change.
Step number two. “Chlorine is added to kill bacteria and viruses. It also helps to remove dissolved hydrogen sulfide.” This is considered a chemical change because we are adding a chemical to the water being purified. In doing this step the chemical chlorine is killing bacteria and viruses. As well it is removing another chemical hydrogen sulfide. When the chlorine is doing its job we cannot physically see the change it is being done on a microscopic level therefore it being considered a chemical change.
75. What is meant by the term “hard water”? How can hard water be softened?
Water is to be considered “hard” if it contains unusually high levels of dissolved magnesium, and calcium ions. This can be an issue for some people because hard water reacts with soap and it forms an insoluble salt or curds, which then in turn may leave your clothing looking yellow. Hard water can be softened by filtering your water through a household water softener to remove some of the excess magnesium
Step number one where “A coarse screen made of metal bars filters large particles and trash, such as bottles and cans.” This would be considered a physical change because there is no chemical process taking place. As well you are able to see a physical change in the water due to trash and debris being filtered out by nothing more then a screen. This screen is doing nothing more other then stopping trash larger then its bars pass through. Thus, making it a physical change.
74. c) Select one example of a chemical change from your table, and explain why it is a chemical change.
Step number two. “Chlorine is added to kill bacteria and viruses. It also helps to remove dissolved hydrogen sulfide.” This is considered a chemical change because we are adding a chemical to the water being purified. In doing this step the chemical chlorine is killing bacteria and viruses. As well it is removing another chemical hydrogen sulfide. When the chlorine is doing its job we cannot physically see the change it is being done on a microscopic level therefore it being considered a chemical change.
75. What is meant by the term “hard water”? How can hard water be softened?
Water is to be considered “hard” if it contains unusually high levels of dissolved magnesium, and calcium ions. This can be an issue for some people because hard water reacts with soap and it forms an insoluble salt or curds, which then in turn may leave your clothing looking yellow. Hard water can be softened by filtering your water through a household water softener to remove some of the excess magnesium