Objective:To illustrate thermal shock and the effects of differing amounts of modifier on the properties of glass. Description: · Three different types of glass rods will be heated so that students can observe the amount of thermal shock that occurs. · Different formulas of glass affect the mechanical, electrical, chemical, optical, and thermal properties of the glasses that are produced. · The two most important properties that determine resistance to thermal shock in glass are thermal conductivity and coefficient of thermal expansion.
· Pressure generates charges on the surface of piezoelectric materials. This direct piezoelectric effect converts mechanical energy into electrical energy. · Conversely, the inverse piezoelectric effect causes a change in length in this type of material when an electrical voltage is applied. This effect converts electrical energy into mechanical energy. · Piezoelectric materials are everywhere and used every day
When heat is transferred, it must have physical matter to move through. · Heat can transfer through conduction, which happens when heat vibrates the atoms in a material which then transfers energy to other atoms in a process called thermal conductance. · Gases, such as air, contain very little matter in comparison with solids or liquids and, therefore, “insulate” heat from flowing. · Refractory bricks are made from ceramic fibers that can withstand extreme temperatures without melting. ◊The bricks are very porous, meaning a large amount of air is trapped between the ceramic fibers, which slows the movement of heat through the material. ◊A similar material was used on the space shuttle to protect it and the crew from outside temperatures of >1200°C achieved upon re-entry of the shuttle into the Earth’s atmosphere.
Objective: to demonstrate how the motion of atoms under added heat can change the shape of metals Description: · During this demonstration, a nanoscale change is impacting the macroscale. · Shape-memory alloys return to their original shape when heated, while other alloys do not. · Nitinol wire, a shape-memory alloy, will be subjected to heat treatment. · Steel wire will also be subjected to heat treatment. · The behavior of the two wires will be compared and the mechanisms behind each behavior will be discussed.
Jolly Rancher candies will be heated in a beaker until reaching a molten state to demonstrate the glass-liquid transition. · Using wooden skewers or popsicle sticks, candy fibers will be pulled from the molten candy to demonstrate the liquid-glass transition. The fiber will be almost instantly cooled once it is removed from the beaker due to the small diameter of the fiber and the temperature difference between the air and the molten candy. · Students can then eat the cooled fibers to again demonstrate the glass-liquid transition.