CaSO4·2H2O + heat → CaSO4·0.5H2O + 1.5H2O (released as steam) is how we make plaster from gypsum. Note the heat. That heat can be released as plaster sets, or hardens. Think of it as the heat of crystallization.
One might guess that an art teacher knows something about the materials used to make artworks. But maybe the knowledge isn’t any more precise than that of a child making shapes from mud and putting them on a hot sidewalk to dry and harden. In effect, sometimes we know what happens, but we don’t understand why something happens. Example: On Friday, March 23, 2007, the BBC reported that at Giles School and Sixth Form Centre in Old Leake, Lincolnshire, UK, a 16-year-old girl suffered third degree burns because her hands were inside plaster as it set. The child lost her thumbs and most of her fingers. “In the incident a girl was mixing plaster of Paris with water by hand, intending to make a plaster cast of her hand.”*
One might also guess that in a school that specializes in visual arts, the entire staff would understand the chemistry of the materials used to create. One would be wrong. The teacher must have had little knowledge of the heat value in a thick mass of plaster of Paris, a value that can reach temperatures in excess of 100 degrees Celsius (the boiling point).
Partial knowledge is the human way. Think Marie Curie. Not only was Marie the first woman to win a Nobel Prize, but she was also the first scientist to win two such prizes. She is known for her work with radium and polonium, both of which she discovered in pitchblende. On might think that the discoverer of radioactive elements would know the danger they posed. One would be wrong. Marie Curie carried vials of radium in her pockets, leading to her death by aplastic anemia. Seems she didn’t really understand processes associated with her materials.
The stories of the Lincolnshire girl and Marie Curie provide us with a question germane to our own lives. Do I carry a pride fueled by partial knowledge?
Look around. Some people have been injured by mixing ammonia and bleach to make a strong cleaning solution, only to unintentionally produce mustard gas. In a world with tens of thousands of synthesized compounds, all of us, including chemists, have a difficult, if not impossible, task of knowing what is or is not dangerous. Synthetic organic compounds abound, and most of them are toxic. When is the last time you handled atrazine? Ever had water in a plastic bottle? Whew! Safe there, aren’t you? There have been efforts to eliminate Polychlorinated Biphenyls (PCBs). But maybe your bottles have been made with Polyethylene Terephthalate (PET), instead. No worry? So what if a little antimony trioxide leaches into the water?
Like the convenience of the modern world? Like all the materials you use without thinking? Proud of your sophistication and collections? Time to question what we use and how we use it. If even the most sophisticated of us, the brilliant scientist Marie Curie, was unaware of dangers in the very materials she discovered, imagine how unaware all of us are about the materials we accumulate and use some eight decades after her death and the creation of tens of thousands of synthetic compounds.
Is there some lesson in this other than that we’re surrounded by dangerous materials? Yes. And it’s a simple one. In hubris derived from our so-called sophisticated lifestyle, we daily mask our ignorance about the most fundamental materials and processes in our surroundings. We ain’t as sophisticated as we pretend to be.
* http://news.bbc.co.uk/2/hi/uk_news/education/6485481.stm
One might guess that an art teacher knows something about the materials used to make artworks. But maybe the knowledge isn’t any more precise than that of a child making shapes from mud and putting them on a hot sidewalk to dry and harden. In effect, sometimes we know what happens, but we don’t understand why something happens. Example: On Friday, March 23, 2007, the BBC reported that at Giles School and Sixth Form Centre in Old Leake, Lincolnshire, UK, a 16-year-old girl suffered third degree burns because her hands were inside plaster as it set. The child lost her thumbs and most of her fingers. “In the incident a girl was mixing plaster of Paris with water by hand, intending to make a plaster cast of her hand.”*
One might also guess that in a school that specializes in visual arts, the entire staff would understand the chemistry of the materials used to create. One would be wrong. The teacher must have had little knowledge of the heat value in a thick mass of plaster of Paris, a value that can reach temperatures in excess of 100 degrees Celsius (the boiling point).
Partial knowledge is the human way. Think Marie Curie. Not only was Marie the first woman to win a Nobel Prize, but she was also the first scientist to win two such prizes. She is known for her work with radium and polonium, both of which she discovered in pitchblende. On might think that the discoverer of radioactive elements would know the danger they posed. One would be wrong. Marie Curie carried vials of radium in her pockets, leading to her death by aplastic anemia. Seems she didn’t really understand processes associated with her materials.
The stories of the Lincolnshire girl and Marie Curie provide us with a question germane to our own lives. Do I carry a pride fueled by partial knowledge?
Look around. Some people have been injured by mixing ammonia and bleach to make a strong cleaning solution, only to unintentionally produce mustard gas. In a world with tens of thousands of synthesized compounds, all of us, including chemists, have a difficult, if not impossible, task of knowing what is or is not dangerous. Synthetic organic compounds abound, and most of them are toxic. When is the last time you handled atrazine? Ever had water in a plastic bottle? Whew! Safe there, aren’t you? There have been efforts to eliminate Polychlorinated Biphenyls (PCBs). But maybe your bottles have been made with Polyethylene Terephthalate (PET), instead. No worry? So what if a little antimony trioxide leaches into the water?
Like the convenience of the modern world? Like all the materials you use without thinking? Proud of your sophistication and collections? Time to question what we use and how we use it. If even the most sophisticated of us, the brilliant scientist Marie Curie, was unaware of dangers in the very materials she discovered, imagine how unaware all of us are about the materials we accumulate and use some eight decades after her death and the creation of tens of thousands of synthetic compounds.
Is there some lesson in this other than that we’re surrounded by dangerous materials? Yes. And it’s a simple one. In hubris derived from our so-called sophisticated lifestyle, we daily mask our ignorance about the most fundamental materials and processes in our surroundings. We ain’t as sophisticated as we pretend to be.
* http://news.bbc.co.uk/2/hi/uk_news/education/6485481.stm
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