Animations for Chemistry Activities & Demos
These 10 – 30 second, unnarrated animations are chemically accurate representations of what's happening on the atomic level in some common chemistry outreach activities. Use them to help illustrate your activity. Or, add your own narration and include them in your chem demo video (remember to credit ACS and Visual Science)!
All animations were developed for ACS by Visual Science in 2021.
Ethanol Evaporation
The evaporation of ethanol on a molecular level
Ethanol (C2H5OH) molecules stay in the liquid phase due to attraction among molecules. When a few molecules at the surface absorb a little energy from their neighbors, they are able to enter the vapor phase. When the atmosphere above the liquid has as much ethanol as it can hold, a few molecules will return to the liquid while others evaporate, forming a dynamic equilibrium.
Magnesium hydroxide and acetic acid reaction
The reaction of magnesium hydroxide with acetic acid in aqueous solution
Only tiny amounts of magnesium hydroxide (Mg(OH)2) can dissolve in water at a time; what does dissolve promptly splits into Mg2+ and OH- ions. Because OH- is basic, adding acid neutralizes it to form H2O, allowing more magnesium hydroxide to dissolve. Continuing to add acid will eventually eat away all the magnesium hydroxide.
Use with: Rainbow Tornado
Alginate polymerization
The polymerization of sodium alginate by calcium chloride
Sodium alginate consists of long chains of tiny clusters of sugars. Each cluster has a negatively charged carboxylate group (--CO2-), which bonds to a sodium ion (Na+). When the sodium alginate meets the calcium chloride in solution, the calcium ions (Ca2+) displace the sodium ions. The +2 charge on the caldium ions allows it to bond to 2 carboxylate groups on the alginate molecules, causing the long polysaccharide molecules to clump together. The clumped polymers form an even bigger polymer that is too big to stay in solution, resulting in a goo.
Use with: Goo Worms
PVA polymerization
The polymerization of polyvinyl alcohol with borate ions in aqueous solution
Polyvinyl alcohol ([C2H4O]n) molecules are long chains of carbon covered with hydrogens and –OH groups. When dissolved in water, borate becomes B(OH)4. When the two compounds interact, the boron replaces one of its -OH groups with an -OH group from a polyvinyl alcohol molecule, kicking off a hydrogen in the process. The hydrogen bonds with the freed -OH to become water.
The boron repeats this process three more times, bonding to a total of four different sites on polyvinyl alcohol molecules. As a result, the polyvinyl alcohol molecules become a tangled mess that forms a gooey slime polymer.
Iodide/starch intercalation
The color change resulting from the intercalation of iodide (I3-) ions into helical starch molecules
Starch is made of long chains of sugar molecules, which often take on a helical shape. When iodide ions are present, they work their way into the centers of the starch molecules. The resulting iodide/starch complex turns the formerly white compound a deep blue-purple.
Use with: Fruit Juice Sleuth
Electrolysis of water
The electrolysis of water hydrogen and oxygen molecules
When water is electrolyzed, electrons flow through the cathode (graphite electrodes shown here) into the water; the hydrogen in the water molecules is reduced to form H2 gas, leaving OH- ions in solution.
Meanwhile, at the graphite anode, electrons flow into the anode, oxidizing the oxygen in water is oxidized to O2 and leaving H+ ions in solution.
Red cabbage indicator color change
The chemical basis of the color changes in red cabbage acid/base indicator
The anthocyanin molecule in red cabbage is responsible for its distinctive color and is often extracted for use as an acid/base indicator. In acidic solution, H+ is added to the -C=O oxygen on the anthocyanin, forming =C-OH; this also adds a double bond to the oxygen-containing ring, and the resulting molecule looks pink. When the pH rises above 7, hydrogens are stripped off the molecule, and the solution turns greenish-blue.
Use with: Rainbow Tornado, Red Cabbage Indicator
Copper verdigris formation and reduction
Animation depicting the chemical changes that occur to create copper verdigris
Copper oxidizes easily in air, so most copper already has a thin layer of CuO on its surface. Acetate from acetic acid solution easily bonds with the CuO to form verdigris which precipitates onto the surface when the water evaporates. Iron can protect copper; the verdigris can react with an iron surface, oxidizing the iron to iron(II) acetate and reducing the copper to copper metal on the iron’s surface.
Sugar dissolution and hydrolyzation
Sucrose undergoes a physical change, then a chemical one
Not all changes indicate chemical reactions. When sugar dissolves in water, water molecules attract the sucrose molecules away from the solid and into solution; however, the sugar molecule remains intact. This is a physical change.
In contrast, the first chemical change in the caramelization of sugar is hydrolysis. In this reaction, a water molecule reacts with the sucrose molecule. Bonds in both molecules are broken and new ones formed, resulting in different molecules.
Absorption of water by sodium polyacrylate
An animation illustrating how sodium polyacrylate molecules attract water molecules
Sodium polyacrylate is a super-absorbing polymer. It is comprised of long chains of carbon atoms, with every other carbon bonded to a negatively-charged carboxylate group (--CO2-). Each carboxylate is bonded to a sodium ion (Na+). When water is added, the water molecules surround the sodium ion, pushing apart the polyacrylate molecules. The result is that the solid sodium polyacrylate powder swells into a gel with the water trapped inside. Sodium polyacrylate has a variety of uses, such as diapers, pads, bandages, air fresheners, artificial snow, growing toys, fire retardants, anti-flood bags, and hot/cold gel packs.
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