Physical and Chemical Properties of Oxygen
Oxygen is the most abundant element in the earth's crust and ranks third in abundance in the known universe. It is necessary for the support of plant and animal life.
In this project, you will chemically produce oxygen and test for the presence of the gas. The physical and chemical properties of the gas will be examined. You will also look at the role of plants in the production of oxygen in the atmosphere as well as the corrosive effect of acid rain.
Purpose: To produce and test for the presence of oxygen gas.
- baby-food jar (or other small glass jar)
- uncooked ground beef (hamburger meat)
- cookie sheet
- 3% hydrogen peroxide
- long, tapered candle
- Fill the jar half full with meat.
- Set the jar in the center of the cookie sheet.
- Fill the jar with hydrogen peroxide.
- Hold the candle at the end away from the wick and light the wick with the match.
- Allow the candle to burn for about 15 seconds, then blowout the flame and insert the glowing wick into one of the larger bubbles that has formed on the surface of the liquid in the jar. Note: It is important that the wick be red hot when it touches the wet bubble (see Figure 26.1).
- Blowout the candle and lay it on the cookie sheet to cool.
CAUTION: It is not safe to repeat the experiment with the same candle because the wick becomes ragged and difficult to blowout.
Results: The glowing wick bursts into flame.
The decomposition of hydrogen peroxide, H2O2, is a safe method of preparing oxygen gas. Hydrogen peroxide decomposes slowly at room temperature but, in the presence of a catalyst (chemical that changes the rate of a reaction), decomposes more quickly. In this experiment, an enzyme (organic molecule that acts as a catalyst)—catalase—is used to increase the breakdown of hydrogen peroxide into water and oxygen molecules. The reaction is as follows:
The test commonly used to identify oxygen gas is one by which a hot, glowing material bursts into flame when it is placed into a container of oxygen. Three requirements are necessary for burning to take place. The first is the presence of fuel (something that burns). The second is the presence of oxygen. The third is a kindling temperature (minimum temperature necessary for a substance to start burning). In this experiment, the wax is the fuel. Each bubble at the mouth of the jar is filled with oxygen. The glowing wick has enough energy to provide the kindling temperature, which is lower for pure oxygen than for air, since only about 21% of the air is oxygen.
Try New Approaches
- Does temperature affect the speed of the oxygen-producing reaction? Repeat the experiment using three jars. Half fill each jar with hydrogen peroxide. Set one jar into each of the following water baths.
- Cold bath: Set the jar in a cup and surround it with ice.
- Moderate bath: Set the jar in a cup and fill the cup with cold tap water.
- Hot bath: Set the jar in a cup and fill the cup with hot tap water.
After five minutes, add equal amounts of meat to each jar and compare the speed of the oxygen bubbles produced. Are the bubbles larger in any of the jars?
- Catalase is present in other kinds of living tissue, but do they contain the same amount? Repeat the original experiment two times, first using small pieces of potato, and then using small pieces of beef liver. Compare the amount and size of the bubbles produced by each food to determine the amount of enzyme present