Semi-conductor
2 Minutes
Semiconductors and metalloids for students: explore how silicon conducts electricity when heated and how metalloid alloys work. An English science lesson.
- Testing an iron nail, wood, and heated silicon wafer in a circuit
- Metal and non-metal properties of silicon and boron
- How metals combine to make alloys, like gold and copper jewelry
What this lesson teaches
A semiconductor is an element that can behave as both an electrical conductor and an insulator depending on the conditions, such as temperature. While conductors let electricity flow freely and insulators prevent it from passing, semiconductors conduct electric current only under certain situations.
Testing materials in a circuit
- Placing an iron nail into an open electrical circuit allows electricity to flow and lights up the bulb, showing that iron is a conductor.
- Placing a piece of wood across the circuit gap does not light the bulb, proving that wood is an insulator.
- A cold silicon wafer placed in the circuit behaves like an insulator and leaves the bulb unlit.
- Heating the silicon wafer enables it to conduct electricity, causing the bulb to light up.
What defines a metalloid
A metalloid is an element that shares properties of both metals and non-metals. Scientists identify seven elements as metalloids, including boron, silicon, and germanium. Silicon, for instance, has a shiny appearance like a metal, but it lacks malleability and ductility, which are properties found in metals. Because silicon combines physical features of both metals and non-metals, it is classified as a metalloid.
Boron and its properties
Boron is another metalloid that displays a mix of metallic and non-metallic traits. It has a shiny surface, which is a physical property typical of metals. Chemically, however, boron behaves like a non-metal because it is highly inflammable and catches fire easily. When boron burns, it produces a bright green flame, which is why it is used in Diwali firecrackers.
Combining metals to form alloys
Metalloids can combine with metals to form substances called alloys. An alloy is created when one metal combines with another metal. For example, ornaments cannot be made out of pure gold alone because pure gold is extremely soft and breaks easily. To make jewelry strong and durable, makers mix a small amount of copper into the gold.