Is ice heavier than liquid water?

No it is not. It weighs less. Water is one of the few compounds that is less dense in its solid state.

No. Water forms a crystal structure when freezing, increasing its volume and decreasing its density.
That is why icebergs exist, and why rivers and lakes have the ice layer on top, and not on the bottom.

Ice can sink in bad movies though.

Water reaches its maximum density at 39.2 degrees Fahrenheit (4 Celsius).

To be clear about this, the reason ice floats is that it is less dense than liquid water. The proportion of the ice cube that is beneath the surface is the fraction of water density that it has.

Humans are also less dense than water, which is why you can do a back float.

A pound of feathers and and a pound of iron nails both weigh a pound; same with a pound of ice and a pound of water they both weigh the same

@Tropical_Willie But the question posited a gallon which is volume, not weight.

I thought a galleon is a type of ship.

Ice weighs less, explained well by @ragingloli.

When I freeze liquid in a bottle, I always make sure there is some space for the liquid to expand into.

Side note: As far as floating. When I was a kid it was so much harder to float, especially my lower legs would sink. Now that I’m fatter I float with no problems. Lol. I remember learning how to tread water for safety in the water, and now I’m not even sure I can sink if I just lie on my back.

Back when I was a kid, I could walk on top of the slightly hardened snow, without breaking the surface, but now the concrete cracks beneath my feet.

Ice floats in water so it is lighter.

A “gallon” is a measure of volume…not mass. A gallon of ice and a gallon of water would fill the same space (assuming no significant gaps in ice cubes or a solid block of ice), but they would not weigh the same. Because of the form of the water molecule, when it solidifies, it joins in a pattern that results in more space being taken up than with liquid form. It is, in fact, less dense. So for the same volume, ice would weigh less. That is also why ice floats.

Even if ice and water had the same density, the bucket of cubes must weigh less than either the bucket of water or the same bucket of water when frozen. This is simply because no distribution of cubes is as efficient in orderly arrangement at packing the bucket. One of the wonders of the second law is that it drives nature toward that most efficient ordering. It’s always that lattice of crystals, and you’ll never find a lake freezing into cubes.

@seawulf575 and @ragingloli gave the best answers.

No it it obviously is not because ice floats in water because it is lighter.

Put an ice cube in a glass of water and see for yourself.