When water is frozen it weighs the same and sometimes a bit less than when it was liquid.
I tried this experiment before with my kids and we weighed a bottle of water when it was just liquid.
Then we froze the bottle of water and then weighed the frozen bottle of water and it actually weighed a few ounces less than it did when liquid.
So water will tend to weigh slightly less when frozen.
If you take the same amount of water and weigh it when liquid and then freeze the same amount of water and then weigh it frozen it will be either the same weight or slightly less in weight.
The matter of the water actually stays the same even though it changes from liquid to frozen.