Water pressure vs temperature If I have a sealed enclosure full of water (constant volume) at 25˚C at atmospheric pressure, I then heat the water to 50˚C. Would the pressure in the sealed enclosure change?
If the pressure has changed, how would I go about calculating the change?
 A: Yes, at constant density, the pressure increases as the temperature does:
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For example, having water sealed at atmospheric pressure at $4\sideset{^{\circ}}{}{\mathrm{C}}$ will have a density of approximately $1 \frac{\mathrm{g}}{\mathrm{cm}^3}$. If we increase the temperature to $30\sideset{^{\circ}}{}{\mathrm{C}}$, maintaining the density (since the enclosure is sealed), the pressure will rise up to $100 \, \mathrm{bar}$.
Find equations describing the rate of change here.
A: If the volume is constant (the container is very stiff/rigid), the rise in pressure would be dramatic indeed. In fact, that is the whole purpose of involving pressure tanks in all enclosed fluid circuits; otherwise the rise in pressure would quickly trigger the safety valve (hopefully present), and if absent, damage the installation.

A: To a very good approximation, liquid water can be treated as incompressible, and therefore the pressure would not have increased.  In practice, the pressure would be determined by the ambient pressure outside of the container, because no container is infinitely rigid.
An exception to this would be if the ambient pressure were low enough such that $50\sideset{^{\circ}}{}{\mathrm{C}}$ were above the boiling point of water at that pressure.  In that case the water would try to boil.  If the container were rigid enough to contain the water, the pressure would increase until the boiling point at that new pressure were $> 50\sideset{^{\circ}}{}{\mathrm{C}}$.  If the container were not rigid enough (to support the pressure difference between that internal pressure and whatever the outside ambient pressure is), then it would rupture and fail.
