Vanishing Volume

IMG_1434

When 50mL of water are added to 50mL of ethanol in a 100mL graduated cylinder, there are only ~97mL of liquid. Ethanol and water molecules are attracted to each other through hydrogen bonding. The two molecules pack closer together with each other than they do with just themselves.

Liquid Nitrogen Ice Cream

22792J_07.15.11_256

Liquid nitrogen is -196˚C and quickly freezes the ingredients into ice cream. The nitrogen boils out leaving deliciously creamy ice cream. The “fog” that we see is condensed water vapor though, not nitrogen gas.

Sodium Hydroxide in Water

sodium hydroxide ions in solution

When sodium hydroxide is dissolved in water it feels warm, which indicates an exothermic reaction.
NaOH (s) → Na+ (aq) + OH- (aq)

Rainbow in a Beaker

densities of sugar solutions layering liquids

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.

Mushroom Cloud

dry ice mushroom cloud bubble

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.

M&M Color Wheel

M&Ms in water, candy coating dissolving

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.

Hot – Cold Water

hot water rises cold water sinks

Hot water expands so it is less dense than room temperature water. Cold water contracts so it is more dense than room temperature water. The red hot water rises and the blue cold water sinks.

Gold and Silver Pennies

plating pennies with zinc silver pennies gold pennies

This demo uses sodium hydroxide to plate Zn on the surface of a copper penny, making it appear silver in color. Zinc is oxidized in sodium hydroxide. The remaining electroplating process is not fully understood. The silvery penny can be heated to melt the zinc and copper together, creating a gold colored alloy.

Electrocute a Pickle

pickle electrocution

When electricity is passed through a pickle, it is conducted through Na+ and the Cl- ions that are present in the pickle. The electricity excites the electrons to a higher energy state, and when the fall back to ground state they emit a yellow/orange light.

Diet and Regular Soda

diet soda floats regular soda sinks coke

Diet soda contains artificial sweeteners while regular soda has sugar in it. Artificial sweeteners are so sweet so only a small amount is needed, where as much more sugar is needed to achieve the same sweetness. Because regular soda has more mass in the same size can, it is more dense than the diet soda.

Color Tornado

food coloring tornado in water on a hot plate

In this demo, food coloring is added to a stirring beaker of water to create a tornado of color. This could be used as an example of a physical change, or to demonstrate the importance of properly mixing solutions.

CO2 Bubbles

dry ice soap bubbles

CO2 gas from subliming dry ice gets caught in a soapy solution creating a column of bubbles. When the bubbles are popped, the “fog” that we see is condensed water vapor, not carbon dioxide gas.

Ammonium Nitrate in Water

ammonium nitrate ions in solution

When ammonium nitrate is dissolved in water it feels cold, which indicates an endothermic reaction.
NH4NO3 (s) → NH4+ (aq) + NO3- (aq)