Day 2: Reactions

Activity 2: Activity Series of Metals

As you saw yesterday, sometimes metal atoms and metal ions in solution can react to exchange places, with the metal atoms becoming ions and the ions becoming atoms. For example, you made silver metal atoms from silver ions when you added a copper penny to silver nitrate solution. Yet you needed to apply electrical energy to the nickel to make the copper ions become atoms (and coat the nickel). If we perform a series of experiments, we can determine which combinations of metal atoms and ions will react (like copper metal and silver ions). This is called the Activity Series for metals. Below you will see the results of a number of different metals with metal ion solutions along with the results that you found.

Results of the Experiments
(The Results Table Show the Combinations
of the Metals / Solutions)

Click to Enlarge

Click to Enlarge

Activity 3: Making Hollow Pennies

Prior to 1983, pennies were made of 95% copper and 5% zinc. However, since 1983, pennies are made by coating a zinc metal core with a thin layer of copper metal (because copper is more expensive than zinc). You determined in activity 1 that copper doesn't react with hydrochloric acid (HCl), while zinc metal does. A hollow penny can be made by taking a file and nicking the edge, exposing the zinc metal core, and then placing the penny in HCl solution. The zinc core will eventually dissolve in the acid, leaving the thin layer of copper and a "hollow penny". The video of the zinc core reacting and dissolving in the acid (the gas produced is hydrogen) and a picture of the final hollow penny are shown below.

Activity 5: Using Red Cabbage Juice as a pH (Acid/Base) Indicator

Red cabbage juice can be used to determine whether a solution is acidic (pH less than 7) or basic (pH greater than 7). In the video and picture below, you see the results of testing some household solutions with cabbage juice to determine if they are acidic or basic?

The results of the experiment.

Click to Enlarge

Activity 6: Flame Tests to Identify Metals

To determine the identity of a metal, we can perform a flame test. When a solution of a metal ion can be placed into a flame, the flame will change colors. Each metal has a unique color and so the types of metals in the solution can be determined from the color of the flame. The different colors of fireworks are made by adding the appropriate metal salt to the fire work. For example, strontium is used to create red fireworks, copper salts to make green fireworks, etc. In the video below, you will see a flame test with strontium (red) and lithium (purple/red) solutions and finally, the combustion of magnesium metal, which produces a very bright white light and extremely hot flame.

Demonstration: Chemiluminescence

Dr. Waner demonstrated a chemiluminescent reaction, which produces mostly light not heat. The video below shows the reaction of luminol. You can perform a chemiluminescent reaction by cracking a light stick.

Demonstration: Reaction of Dry Ice (Solid Carbon Dioxide) with Water

Dr. Waner demonstrated that when dry ice (solid CO2) is added to water, the solution becomes acidic, as shown by the change in the acid/base indicator.

Demonstration: Rainbow Connection

Dr. Waner demonstrated the use of acid/base indicators with the help of Kermit the Frog's song. After today, can you explain what is happening?

Demonstration: Methanol Cannon

Dr. Waner demonstrated the reaction of methanol with oxygen (combustion) that is caused by a spark. This is similar to what happens in a car's engine. See the video below.

Activity: Mentos and Diet Soda

When mentos are added to diet soda, the carbon dioxide that is dissolved in the soda becomes gaseous, creating a spectacular result.