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...or IS the inside temperature ambient temperature? Surely the insulation of the container is not sufficient to seal in that cold? I.e. if you had an unsealed bowl of liquid nitrogen with the same thickness of the sealed canister surely the temperature of that bowl on the outside would be cold?

Liquid nitrogen is usually kept in a Dewar flask. This flask protects the liquid nitrogen against all three kinds of heat transfer, as follows:

1) Convective heat transfer is largely eliminated because there is a hollow space inside the flask, between the outer and inner walls (or "containers") of the flask. This hollow space often is vacuumed out to eliminate heat convection via air.

2) Conductive heat transfer is largely eliminated because the inner container only touches the outer container at the very top of the flask, so any heat conduction from the mouth of the flask must travel the maximum path length to get to the liquid nitrogen. Accordingly, the rate of conductive heat transfer is minimized by doing this.

3) Radiative heat transfer is largely eliminated by putting a mirror finish on the outside of the inner container.

All of these techniques mean that heat transfer from the outside of the Dewar flask to the inside of the flask is minimized, and as a consequence, the outside of the flask does not feel cold.

For more info, see the following:

https://en.wikipedia.org/wiki/Vacuum_flask

https://en.wikipedia.org/wiki/Cryogenic_storage_dewar

Gas molecules have higher energy than a molecule that is part of a liquid or solid. Their higher kinetic energy allows them to move freely and bounce off other molecules and atoms, giving them their gaseous properties.

When a gas is compressed, it forces these high energy particles to get closer together. As they get closer, they aren't able to move as freely. This kinetic energy must be preserved, and is given off in the form of heat to the surrounding container of the gas. Eventually, as pressure increases, these particles will condense together to form a liquid.

When depressurized, as the liquid converts back to a gas, it will absorb the same amount of heat energy that it expelled when compressed. The heat energy in the container will be taken back by the expanding gas, making the container cool down.

As for your question, the temperature of the liquid is ambient but at a very high pressure. Having an unsealed bowl of liquid nitrogen would not last long, and would get very cold as the liquid turned back into a gas.

It has less to do with the static state of the liquid and more to do with the process of going from liquid to gas or vice versa.

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