Eli5 – Why can you tap on a bottle with your fingernail and immediately tell if it’s plastic or glass?

Question

Even without the noise I think I could tell the difference. How?

In: 0

Answer 1

Glass is harder and more conductive of heat than most plastics. Depending on the type of plastic, you may be able to feel the slight give compared to the hardness of glass, but you can definitely hear the difference in the tap. Glass conducts heat better than plastic, so glass will feel cold to the touch at room temperature, while plastic as a poor conductor will tend not to feel cold.