Final answer:
Good thermal conductors like copper and silver efficiently transfer heat due to their free electrons, hence their use in cooking utensils. Plastic and wood are good insulators, making them suitable for utensil handles to prevent burns. Semiconductors like silicon behave as insulators at low temperatures and as conductors when hot.
Step-by-step explanation:
Two materials that are good thermal conductors include copper and silver. These metals are commonly used in items such as cooking utensils because they can efficiently transfer heat. The high thermal conductivity of these materials is due to the large numbers of free electrons that can carry and transport thermal energy.
Conversely, materials such as plastic and wood are good insulators. They do not conduct heat well, which is why they are often used for the handles of cooking utensils to prevent heat transfer and protect from burns. In electronics, silicon and germanium, which are semiconductors, act like insulators at low temperatures and as conductors when hot, giving them diverse applications in electronic devices.