C. Melting ice.
It is C because melting ice is a change of state from solid to liquid which requires an addition of energy(or entropy) into the system.
Condensation of water occurs from a gas to a liquid state, which takes energy out of the system(water) and gives it to the surroundings(air around it). Freezing water is the same as condensation except for the state change. Deposition is simply gas to a solid instantaneously so you can again see it as with the other two examples.
I used an online calculator and got 54.22 m/s. I hope that helps
A covalent bond is the bond formed by the sharing of a pair of electrons by two atoms.
Your answer is D: A bond between two atoms.
Yes it is available. It will continue catalyzing the reactions until it becomes completely consumed. That's how enzymes work. They work and are eventually consumed in the process completely without altering the reaction in any way other than speeding it up.
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B is true because liquids are still more compact than gases, although they are loose, they aren't completely free. They also don't have a definite volume, making them assume the shape of their container. As for compression, liquids are harder to compress compared to gases.
