system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When a tub of ice cream melts and becomes liquid, why is it ruined even after you freeze it back again?

When you freeze the ice cream after it melts from store bought and becomes completely liquid, it doesn’t stay the same way.  It just isn’t ice cream anymore, there’s no cream, it becomes like frozen ice lolly kinda texture; completely different from the texture it comes in ie. Soft, fluffy, milky, creamy.
gpt
When you make ice cream it is churned constantly while it freezes. Ice cream makers also have blades that scrape the ice off the inside walls of the vessel since that freezes first. Keeping all the ice cream moving like this as it freezes keeps the ice crystals that form very small. The small ice crystals is what gives fresh ice cream that smooth texture.  When the ice cream has melted and is then refrozen you get much larger ice crystals, which is why it kinda has the texture of a bad snow cone now.