Ceramics and Glass 8 th Grade Chemistry

Ceramics Ceramics are hard, crystalline solids made by heating clay and other minerals materials to high temperatures. Clay is water and small mineral particles such as silicon, aluminum, and oxygen. Clay forms when the minerals in rock break down

Making Ceramics When a clay object is heated above 1,000 degrees C, much of the water present evaporates, and the other particles stick together. This process forms bricks and flower pots. These items have tiny spaces that absorb and hold water. Potters sometime put a thin layer of silicon dioxide and reheat the clay. This process forms a glassy water proof coating called a glaze.

Properties of ceramics Ceramics resist moisture, do not conduct electricity, and can withstand temperatures that cause metals to melt. Used for thousands of years to store food, protecting it from moisture and animals. Roofing, sewer pipes, bricks Insulators in electrical equipment and light fixtures.

New Uses Human hips, knees and other body parts. Catalytic converters in cars- help convert harmful exhaust gases into harmless carbon dioxide and water.

Glass Thousands of years ago people learned that sand mixed with limestone can be melted into a thick, hot liquid that flows like molasses. If it cools quickly it forms a clear solid structure with no crystals.

Making Glass Early glass makers added calcium and sodium to the melting sand. This mixture melts at a lower temperature, so it is easier to work with. Windows, bottles and jars are still made with this type of glass. 2,000 years ago glassmakers in ancient Syria invented glassblowing. Put a blob of melted glass on an iron pipe. Then they would blow air through the pipe, making a hollow glass vessel.

Properties of Glass Glass is brittle and can shatter when struck. Glass is clear, can be made in many shapes and colors, and can’t be penetrated by liquids. Different materials can be added to make it more useful. Adding lead oxide instead of limestone, makes it bend light- eyeglasses, telescopes, and microscopes. Adding boron oxide makes it resist heat better. Cookware and laboratory glassware.

Communication An optical fiber is a threadlike piece of glass (or plastic) that can be used for transmitting light. When you speak through a telephone, the signal created by your voice is converted to light signals that can travel through the glass fiber. At the other end the light is converted to electronic signals that can be converted to sound. A pair of optical fibers the thickness of a human hair can carry 625,000 phone calls at one time. One ¼ lb. of glass fiber can replace more than 2 tons of copper wire. Glass does not corrode- underwater/ocean lines