Video Transcript
At lower temperatures, it is safe to heat small amounts of a solid in a test tube. However, when heating a solid at a higher temperature for a longer period of time, what apparatus, frequently made of porcelain or stainless steel, is more commonly used? (A) Watch glass, (B) crucible, (C) pipe clay triangle, (D) round-bottom flask, or (E) Erlenmeyer flask.
The question mentions that lower temperatures are used to heat a solid in a test tube. Test tubes are typically made of either glass, for general chemistry work, or borosilicate glass, which can withstand higher temperatures before cracking. Test tubes can withstand temperatures of several hundred degrees Celsius. They can be heated for longer periods of time at lower temperatures in the range of about 200 to 230 degrees Celsius and for a shorter period of time at temperatures up to about 400 degrees Celsius before cracking.
The question also tells us that at higher temperatures and longer periods of time, a heating apparatus, usually made of porcelain or stainless steel, is more commonly used. Which apparatus is this? This apparatus is called a crucible. Crucibles can withstand heating at temperatures over 800 degrees Celsius. These porcelain or stainless-steel vessels consists of a cup, which holds the solid material to be heated, and a lid. The lid can be used to prevent substances which have been released from the heated solid from reentering the crucible.
Typically, during heating, a crucible is placed on a pipe clay triangle, which looks like this from above. Heat can easily reach the crucible and its contents through this open section in the center. The clay triangle is usually placed on a tripod stand and the contents of the crucible heated with a Bunsen burner flame.
Finally, which apparatus, commonly made of porcelain or stainless steel, is used at higher temperatures for longer periods of time to heat solids? The answer is (B) crucible.
