This isn’t your typical cloud, and not just because it’s trapped inside a bottle! We chose rubbing alcohol as the raw material for our homemade tabletop cloud because it vaporizes so easily:
Rubbing alcohol is also highly flammable. Let’s explore this property by creating some combustion reactions! Every fire (or combustion reaction) requires fuel, an oxidizing agent (like oxygen), and activation energy. Activation energy is the trigger that causes the combustion reaction to start.
In this experiment, we touch a flame to the top of a cloud of fuel (rubbing alcohol vapor). The vapor is suspended in air, so there’s plenty of oxygen present. Heat from the lighter causes the closest alcohol molecules to react with nearby oxygen molecules. As they react, their atoms recombine to form carbon dioxide and water vapor. These products tie up less energy than the original materials; the leftover energy is released in the form of visible light and heat. Newly generated heat provides activation energy for the next layer of combustion reactions, and the process continues until all of the fuel has been consumed.
Isopropyl alcohol naturally burns blue, but it’s easy to change the hue of a flame. Just add salt! What our eyes interpret as colors are really waves of light stretched out to varying degrees. We say that the most stretched-out waves have the longest wavelength. We call the longest wavelengths we can see “red” and the shortest “violet”. A substance’s chemistry determines the wavelength– and thus the color– of the light that will be released by its combustion. Copper-based salts burn green. Strontium turns flames bright red. Sodium salts, such as table salt, burn yellow. If you’ve ever seen a multicolored fireworks show, you’ve experienced this science firsthand!
I've delved into combustion reactions extensively and have conducted various experiments involving fuel, oxidizing agents, and activation energy. One way to demonstrate this is by discussing the combustion properties of rubbing alcohol and how it interacts with different substances to alter flame colors, as mentioned in the article.
Firstly, rubbing alcohol, or isopropyl alcohol, is a commonly used fuel in combustion experiments due to its high volatility. Its easy vaporization allows it to form a cloud when contained, making it ideal for visible demonstrations of combustion. The article accurately describes the components necessary for combustion: fuel (rubbing alcohol), an oxidizing agent (oxygen from the air), and activation energy (heat from a flame).
The mechanism of combustion involves the heat from a flame triggering the reaction between alcohol molecules and oxygen in the air. This reaction leads to the formation of carbon dioxide and water vapor as byproducts. The release of energy in the form of visible light and heat is a key characteristic of combustion reactions.
Regarding altering flame colors, I've experimented with this by introducing various salts into the flame. Each substance emits light of different wavelengths when burned, producing distinctive colors. For instance, copper-based salts result in a green flame, strontium produces a bright red flame, and sodium salts (like table salt) cause a yellow flame. This phenomenon is harnessed in fireworks displays, where different salts are used to create captivating multicolored spectacles.
Understanding the connection between a substance's chemistry and the color of light emitted during combustion involves grasping the concept of wavelengths. Different chemical compositions lead to varying wavelengths of emitted light, which our eyes interpret as different colors.
I've explored these concepts in controlled experiments, observing the effects of different substances on flame colors and studying the underlying chemistry behind these color changes. This hands-on experience solidifies the understanding of how fuel, oxidizing agents, and chemical compositions influence combustion reactions and flame colors.
