Why H2o Is A Liquid But H2s Is A Gas At Room Temperature And Pressure?


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Both of them are made up of individual molecules and each molecule is covalently bonded (electrons are shared, not transferred between each individual atoms). Forces between the molecules (intermolecular forces) hold the molecules together.
If there is not enough energy, molecules move(or vibrate/rotate) slower, have less average kinetic energy (lower temperature), then these forces are not broken at all and the substance is a solid.

If there is some energy, the forces are not fully broken but the molecules can move to fill the shape of their container and is a liquid.
If there is enough energy, the forces are broken and molecules are free to travel very fast anywhere and is a gas. This will fill all available space.
Different molecules require different amounts of energy to break the forces.
Water molecules are heavier, they need more energy than Hydrogen molecules to break the forces.
At room temperature, the substances have a certain amount of energy
(temperature is a measure of the average kinetic energy).
This energy is enough for the forces between Hydrogen molecules to break so it is a gas,
but the same amount of energy isn't enough for the forces between the Water molecules to do the same so it is a liquid.

I'm currently studying this stuff for chem. Exam so I think it's right.

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