How can I cut easy some materials like a tomato and some materials like gold not?

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How can I cut easy some materials like a tomato and some materials like gold not?

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A tomato is mostly water, and water is really easy to cut through. The molecules that make up water aren’t bound tightly together.

Gold, however, is _much_ more tightly bound together than water. The atoms of gold are fixed into a rigid shape that needs to be broken apart by a knife that’s really sharp

Not all solids are created equal. Some are hard, with strong intermolecular bonds that allow the material to resist abrasion and deformation. Some isn’t. Gold is a metal. It’s not as solid as the other metals (in fact it can be worked and deformed quite easily at room temperature), but it’s still more solid than the fibers that make up a tomato.

Don’t forget that a tomato is mostly made up of water, too.

Everything is made of small particles. The smallest particles are called atoms. Sometimes they form bigger particles called molecules. A tomato isn’t one solid object but instead is billions of molecules connected together with basically magnetic charges.

Like real magnets, if you apply enough force to two molecules you can break them apart. The stronger these “molecular bonds” are, the harder it is to break the molecules apart.

Stuff that is easy to cut has weaker molecular bonds, so it takes less pressure for a knife to break the bonds. Stuff that is hard to cut has stronger molecular bonds, so it takes a lot more pressure to break them. If the bonds of the thing you’re trying to cut are stronger than the bonds in the knife you’re using, you’ll break the knife instead! That’s why we can’t cut diamonds with anything but other diamonds.

So to a 5 year old:
Imagine 2 sets of magnets. A really strong set, and a really weak set.

The magnets represent molecules held together in different objects.

The strong set, you try to push a finger to pry them apart between and its really hard ro get them apart. This is like strong bonds between the gold molecules holding it into a solid.

The weak set comes apart like it’s nothing. Like bonds between water or other molecules that make a tomatoe.