Dented Cans After Refrigeration: Causes, Solutions, and Prevention

What to Do if a Can Dents When Chilled?

Causes:

• Expansion of Water: When water inside the can turns into ice, it expands, causing increased pressure on the can walls, potentially leading to dents.

• Vacuum Effect: When water cools down near 3.98°C, it contracts, creating a vacuum inside the can, which can also lead to dents.

Properties of Water:

Volume and Density: Water has the highest density at 3.98°C. If the temperature deviates from this point, water expands. This is why ice floats on water.

Expansion When Turning to Ice:

Expansion When Freezing: Water increases its volume by about 9% when it transitions from liquid to solid (ice).

Preventive Measures:

1. Reduce Temperature Before Filling: Before filling the can with water, reduce the water temperature to 3.98-6°C to prevent vacuum formation when chilled.

2. Use Flexible Containers: Use cans that can slightly expand, such as those with lids that adjust to internal pressure changes.

3. Avoid Freezing: Avoid chilling the cans to the freezing point to prevent water from turning into ice and expanding.

Additional Precautions:

• Check Can Quality: Use sturdy cans that can withstand the expansion of water.

• Control Transport Temperature: Maintain a moderate temperature during transportation to prevent water inside the cans from freezing.

• Proper Filling: Ensure there is enough space inside the can to accommodate water expansion if it freezes.

By maintaining the quality of cans and preventing dents when chilled, customer satisfaction can be enhanced, and losses during production and distribution can be minimized effectively.

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Properties of Water

Molecular Structure:

• Water Molecule (H2O): Consists of two hydrogen atoms and one oxygen atom connected by covalent bonds, with a 105° angle between them. Oxygen has a negative charge, and hydrogen has a positive charge.

• Hydrogen Bonds: Water molecules are connected by hydrogen bonds, forming a tetrahedral structure, which causes water to occupy more space when it freezes.

Figure 1 Water Molecule

Figure 2 Hydrogen bonds have a distance of 177 picometers, while covalent bonds have a distance of 99 picometers.

Surface Tension:

A clear example of hydrogen bonding is water's surface tension. We can observe that water droplets on a surface or on a lotus leaf are spherical, resembling a convex lens. When a glass is filled with water, the water surface bulges slightly above the rim. Without surface tension caused by hydrogen bonds, the water surface would be flat and level with the glass rim. Surface tension is a special property of water, stronger than that of other liquids except mercury, which is the only liquid element. Surface tension causes water to cohere and seep through every nook and cranny, even through holes and cracks in rocks. Thus, water plays a revolutionary role in shaping the Earth's surface.

State Changes:

At sea level atmospheric pressure, water is in a liquid state. Water changes to a gas (steam) when its temperature reaches the boiling point at 100°C and changes to a solid state when its temperature drops to the freezing point at 0°C. The process of state change in water involves the absorption or release of heat without a change in temperature, known as latent heat. The unit for latent heat is the calorie.

1 calorie is the amount of heat required to raise the temperature of 1 gram of water by 1°C. Therefore, adding 10 calories to 1 gram of water will increase its temperature by 10°C.

Figure 3 Energy Required for Water State Changes

Under atmospheric pressure at sea level, water will turn into a solid state at 0°C. When examining the graph in Figure 4, it is evident that water has the highest density at 4°C and remains in a liquid state. When water changes to a solid state at 0°C, its volume increases by approximately 9%. We can see this when a glass filled with water and placed in the freezer will overflow or cause the glass to break as the ice expands. Similarly, when water in rock crevices freezes, it expands, causing the rock to break and contributing to the weathering process, which produces sediment.

Figure 4 Density of Water at Different Temperatures

Water is a wonder of the universe. Generally, matter becomes denser when it transitions to a solid state. However, water becomes less dense when it changes to a solid state, which is why ice floats on water. If ice were denser than water, as air temperature drops, ocean water would freeze and sink to the ocean floor, making it impossible for organisms living on the ocean floor to survive. Therefore, water becoming less dense when it freezes is beneficial and conducive to life on Earth. When air temperatures drop below freezing, ice forms on the surface of the ocean, acting as an insulator to prevent the underlying seawater from losing heat and freezing completely. This allows marine life to survive in the ocean comfortably.

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Reference List

Lesa 2022. สมบัติของน้ำ - LESA: ศูนย์การเรียนรู้วิทยาศาสตร์โลกและดาราศาสตร์. [online] Available at: https://shorturl.asia/mTIJ4 [Accessed 10 September 2022].