Liquids and solids behave differently when there are changes in pressure. This is because of the way their tiny particles are arranged and bonded together.

1. How They Get Smaller

• Liquids: They generally can’t be squished much. For example, water is really tough to compress, with a special measurement called bulk modulus that is about $2 \times 10^9 \, \text{Pa}$. This means they resist getting smaller when pressure is applied.

• Solids: They are denser and often stronger, but they can be squeezed a little. Their bulk modulus ranges from about $10^9 \, \text{Pa}$ for regular metals to $200 \times 10^9 \, \text{Pa}$ for really hard materials like diamonds.

2. Changes in Size

• Liquids: When you press down on liquids, they don’t get much smaller. For example, if you increase the pressure by $1000 \, \text{atm}$, a liquid might only shrink by about 0.5%.

• Solids: When solids are under a lot of pressure, they can change size more, usually by about 1% or more depending on what they are made of.

3. Changing States

• Liquids: If you put enough pressure on a liquid, it can turn into a solid. For instance, water can freeze into ice if the pressure reaches $2000 \, \text{atm}$.

• Solids: When you push down on solids a lot, they can create new, more compact solid forms. For example, graphite can turn into diamond under high pressure.

In short, liquids don’t shrink much under pressure, while solids can change more significantly.