Ice cream melts in your hand but not in your freezer due to the difference in temperature and the physical properties of ice cream.
Temperature: Ice cream is stored in freezers, which are kept at very low temperatures (typically around -18°C or 0°F). At such cold temperatures, the water in the ice cream freezes and forms ice crystals, creating the solid, frozen texture of the ice cream.
Heat transfer: When you hold ice cream in your hand, the temperature of your hand is warmer than the freezing temperature of the ice cream. Heat naturally flows from warmer objects to colder objects, so the heat from your hand transfers to the ice cream.
Melting point: The components of ice cream, such as sugar, fat, and milk proteins, lower the freezing point of water, making it more difficult for the ice cream to remain solid at warmer temperatures. As the heat from your hand is transferred to the ice cream, it causes the ice crystals to melt and turn the ice cream into a softer, semi-liquid state.
Insulation in the freezer: Freezers are designed to maintain a consistently low temperature. They are insulated to keep the cold air inside and prevent warm air from entering. This insulation helps maintain the low temperature necessary for keeping ice cream solid and prevents it from melting.
In summary, ice cream melts in your hand because the heat from your hand transfers to the ice cream, causing it to warm up and melt. On the other hand, the freezer's low temperature and insulation keep the ice cream solid and prevent it from melting.