Chemistry has a way of presenting us with fascinating and enigmatic reactions, and Devil’s Milkshake is no exception. This intriguing chemical reaction involves the interaction of pure calcium metal with water, resulting in an effervescing display of hydrogen gas, slowly coming out of the solution.
The color of the calcium hydroxide (Ca(OH)2) solution is typically a white solid (making a milky appearance in water), whereas hydrogen (H2) is a colorless gas. Being flammable, hydrogen gas can be put on fire and the solution will start fueling the fire with more and more hydrogen.
The additional element of color change with an indicator adds to the wonder of Devil’s Milkshake, making it an interesting chemistry practical demonstration.
Chemical Reaction
The solution (aka) Devil’s Milkshake is created by dissolving pure calcium metal in water. When calcium (Ca) reacts with water (H2O), it undergoes a redox reaction, leading to the formation of calcium hydroxide (Ca(OH)2) and the release of hydrogen gas (H2):
Ca(s) + 2H2O(l) → Ca(OH)2 (aq) + H2 (g)
Detailed Process
The reaction between calcium and water is not as dramatic as some other alkali metals, like sodium or potassium, which vigorously react and may even catch fire (automatically) upon contact with water.
In contrast, calcium reacts relatively slowly and gently releases hydrogen gas. The evolution of hydrogen gas is a crucial aspect of Devil’s Milkshake, as it contributes to its intriguing property of ‘fire’.
The Devil’s Milkshake Effect
The slow release of hydrogen gas bubbles in the Devil’s Milkshake reaction makes an interesting visual effect. The tiny gas bubbles produced during the reaction tend to adhere to the surface of the calcium, creating a frothy appearance that resembles a milkshake, hence the name “Devil’s Milkshake”.
Color Change with Indicator
But that’s not all—there’s another captivating aspect to Devil’s Milkshake. By adding a chemical indicator to the solution, the color can be changed. A chemical indicator is a substance that changes color depending on the acidity or basicity (pH) of a solution.
When calcium metal reacts with water, it produces calcium hydroxide, which is alkaline. By adding a suitable indicator that changes color in basic solutions, the color of Devil’s Milkshake can be altered, adding a touch of magic to the chemical display.
The phenolphthalein indicator may be applied here because it changes color to violet-pink when the pH of a solution goes above 10.5 (alkaline).
Read more about; When does phenolphthalein turn pink?
Safety Considerations
While the Devil’s Milkshake reaction itself is not excessively hazardous, it is essential to handle pure calcium metal with care. Calcium is highly reactive and should only be handled by experienced individuals with proper safety precautions in place. Additionally, the hydrogen gas produced during the reaction is flammable, so any flame test should be conducted with caution and in a controlled environment.
Concepts Berg
Hydrogen gas (H2).
The slow release of hydrogen gas bubbles creates a frothy appearance, resembling a milkshake.
White or colorless, giving it a milky appearance in the water.
By adding a suitable chemical indicator that changes color in basic solutions, such as phenolphthalein.
Handle with care, as calcium is highly reactive, and perform any flame test with caution in a controlled environment.
References
- The Devil’s Milkshake (chemedx.org)
- Calcium + Water (Angelo State University, San Angelo, Texas, US)
