Sugar solutions that have different concentrations have different densities; the more sugar in a solution the more dense it is. Therefore less dense solutions can be layered on top of denser ones.
This demo picks up an ice cube without lifting it. The salt changes the melting point of the ice cube which “freezes” it to the string, allowing the demonstrator to pick the ice cube up.
Water has a very high surface tension because of the strong hydrogen bonding between water molecules, which allows the pepper to float on top of the water. When a small amount of soap is added it forms a monolayer on the surface. The monolayer spreads away from the point of contact causing the pepper to move to the edges of the dish.
This demo has a solution in a flask that changes color from pink to blue to green to yellow to orange as the solution is stirred. The different colors are due to the different oxidation states of Mn.
When the bill is dipped in the water/alcohol mixture then lit on fire, the water protects the bill from burning. A large amount of the alcohol is vaporized from the heat causing a large flame around the bill.
C2H5OH + 3O2 → 2CO2 + 3H2O
When dry ice is placed in warm water it sublimes very quickly forming a large amount of carbon dioxide gas. When a bubble is placed over this the bubble grows from the pressure.
This demo shows how a precipitation reaction works. The precipitate formed is a common ingredient in chalk.
CaCl2 (aq) + Na2CO3 (aq) → NaCl (aq) + CaCO3 (s)
This demo uses sodium polyacrylate, a super absorbing polymer found in diapers, to turn water into a gel. The sodium polyacrylate has carboxylate anion portions and sodium cation portions. Water is attracted to the sodium ions, thus it enters the polymer through osmosis and the polymer swells and the sodium carboxylate is ionized. The anionic carboxylates on the polymer repel each other, causing the polymer to swell, trap the water, and form a gel. When NaCl is added the increase of electrolytes (ions) in the water shield the repulsion of the carboxylates, thus contracting the polymer and expelling the liquid water.
When M&M’s are placed in water, the outer shell, which is made of sugar, dissolves. The sugar moves from a place of high concentration (the M&M) to a place of low concentration (the water away from the M&M). When the sugar shell dissolves and moves outward, it takes the layer of food dye with it. When more than one M&M is placed into a petri dish the colors do not mix because the concentration of sugar at the interface is approximately the same. Also, around the bottom of the M&M water appears cloudy because the sugar that is dissolved is more dense than the water, so it sinks.
When basic baking soda (NaHCO3) is combined with acidic lemon juice (mainly citric acid, H3C6H5O7) an acid base reaction occurs. The reaction releases CO2 which can be captured using dish soap to form bubbles.
H3C6H5O7 (aq) + 3 NaHCO3 (s) → 3 CO2 (g) + 3 H2O (l) + Na3C6H5O7 (aq)