Final answer:
Ice packs should be stored for a minimum of 24 hours in the freezer to ensure optimal cooling effectiveness. Physics principles explain that a 3.50-kg bag of ice absorbs energy, calculated as an average power of approximately 13.53 watts over a day, to keep the contents of a cooler cold by melting.
Step-by-step explanation:
The subject of your question is Physics, specifically relating to the phase change of ice and energy transfer. To answer your question, ice packs should ideally be stored in the freezer for a minimum of 24 hours to ensure they are thoroughly frozen and will provide effective cooling when used. This time frame allows the ice packs to reach their desired temperature and change phase from liquid to solid, storing energy in the process.
When on a trip, a 3.50-kg bag of ice lasts an average of one day in your cooler because ice has a high capacity for absorbing heat due to its latent heat of fusion. When calculating the average power entering the ice if it completely melts over one day, we use the specific latent heat of fusion of ice, which is 334,000 joules per kilogram. Therefore, the total energy needed to melt 3.50 kg of ice is 3.50 kg × 334,000 J/kg, which equals 1,169,000 joules. Since power is energy over time, and there are 86,400 seconds in a day, the average power is 1,169,000 joules divided by 86,400 seconds, resulting in an average power of approximately 13.53 watts.
The effectiveness of ice in absorbing energy can be crucial for applications like ice boxes, where the melting ice keeps the interior cold. Factors such as the quantity of ice used, thickness of the container, and external temperature can significantly impact how long the ice lasts.