There are many products that are made from both glass and plastic, an example being bottles. The main difference we notice is the hardness. Why?
That's because glass is made up of many small molecules with firm, indivisible bonds. If a sufficient force is applied, the joints are broken. This gives the glass hardness and brittleness.
Transparent plastics, on the other hand, are polymers of very large molecules with loose bonds, not very rigid, so the molecules slide one over the other, making the plastic flexible.
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