Understanding the Science Behind Ice Cream Vendors' Tricks

The Arrival of Summer and the Joy of Kulfi

As summer sets in, the heat becomes increasingly unbearable, especially during the afternoons. With the rising temperatures, our cravings for cold treats intensify. One such favorite is kulfi, a frozen dessert that everyone loves, especially during the hot months. When we feel too lazy to head to the market, the kulfi vendor often appears in our neighborhoods. The sound of his bell signals his arrival, and we instantly recognize that kulfi is just around the corner.

The Kulfi Vendor's Secret

The kulfi vendor operates from a cart, where he keeps all his kulfis nestled in ice. Surprisingly, despite the scorching heat, his kulfis do not melt. This is because he stores them in a box filled with ice. You might wonder why the ice doesn't melt quickly, and the answer lies in the addition of salt to the ice.

The Science of Ice and Salt

Many of you might be curious about the relationship between ice and salt. To understand this, we need to delve into some scientific concepts: freezing point, boiling point, and depression in freezing point. These are topics many of us might have encountered in school science classes, but let's refresh our memories.

The freezing point is the temperature at which a liquid turns into a solid. For instance, the freezing point of water is 0 degrees Celsius, where it solidifies into ice. Conversely, the boiling point is the temperature at which a liquid begins to boil; for water, this is 100 degrees Celsius.

Depression in freezing point refers to the phenomenon where the freezing point of a substance decreases when a non-volatile solute is added. This results in a lower vapor pressure and a higher boiling point.

How Salt Affects Ice

In simpler terms, when salt is mixed with ice, it raises the boiling point, preventing it from melting quickly. Thus, when the kulfi vendor adds salt to the ice, he benefits in two ways: the ice remains solid, and the kulfis stay intact.

Interestingly, the vendor may not even realize the scientific principles at play as he goes about his daily routine of selling kulfis.