🍳 Thermal conductivity
Thermal conductivity occurs when the heat source and the heat receiver touch each other (connected by matter). The heat passes from the warmer body to the colder one through the place where the two bodies are in direct contact. The heat travels as using the molecules of both bodies at the place of their contact.
This process is most often observed in solid bodies. Some materials are better thermal conductors, while others called insulators do not conduct heat.
Which materials are the best conductors?
👀 Observe
You need 3 spoons (metal, plastic and wooden), a lump of butter, and a bowl full of hot water. Ask any older relatives to help you with this.
Scrape some butter with each of the spoons. Now dip the 3 spoons with the butter, in the hot water at the same time.
Did you notice what happened? Which butter melted the fastest?
Yes. The butter in the metal spoon began to melt first.
Metals are among the best conductors of heat. Metals such as aluminum and iron conduct heat very well. But silver and copper do best (some of the best heat conductors).
Usually, metals that are good thermal conductors can also conduct electricity well.
Have you heard about the diamond? It is a crystal, not metal. Diamond is a very good conductor of heat, but it does not conduct electricity.
Do you know that materials that are good thermal conductors, as a rule, are good conductors of sound as well?
Have you noticed that metals look cold when you touch them?
👀 Observe
Leave 3 clean spoons on the table (wooden, metal and plastic). Wait a few minutes for their temperatures to balance. Touch each spoon separately. What did you notice? All three spoons have the same temperature (room temperature), but when touched the metal one it looks colder than the wooden one. Why?
Because metal is such a good conductor of heat that when you touch it, the heat from your hand is quickly transferred to the metal spoon. The metal quickly pulls the warm out of your hand, creating the feeling that it is cold. In fact, your hand loses heat and the spoon absorbs it. That is why most handles of metal pans, pots, spoons (for cooking) are made of material that does not conduct heat (insulator).
What else is heated by thermal conductivity? Look around at home and try to answer. Yes – hot plates. The heated hob heats the pans and pots that we place directly on it. Food that is in the pan or saucepan is also heated by thermal conductivity.
Do you remember the feeling when we drink hot tea or cold juice? Yes? This is also a result of thermal conductivity.
✅ 🧑🎓 Test your skills:
- What is thermal conductivity?
- Where we can see or use thermal conductivity in our daily lives?
- How does the heat travel?
- Is it true that the heat travel from the hotter to the colder body/places?
- What is a thermal conductor? Say 3 thermal conductors around you.
- What is a thermal insulator? Say 3 materials that are thermal insulators around you.
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