Question

"Classifying Matters,

Margot and Janette, who were chemistry lab partners, were carrying out an experiment. They put a soap-free steel wool pad into each of three glass jars. Janette put a thermometer into each jar so that the steel wool pad was wrapped around the thermometer bulb. Then she tightly covered each jar with a lid through which the thermometer fit. Margot read the temperature in each jar after five minutes as being 25°C, which was room temperature. She removed the wool pad from the second jar, soaked it in water that was at room temperature, and returned the pad to the jar, making sure that the bulb of the thermometer was buried within the steel wool pad. She put the lid back on, and read the temperature after five minutes. The temperature had not changed. Janette removed the third steel wool pad, soaked it in vinegar that was at room temperature, squeezed out the excess vinegar, and placed the pad back into its jar, again inserting the thermometer and putting on the lid. After five minutes, Margot noted that the temperature inside the jar containing the steel wool and vinegar had increased to 29°C. The students then let the three jars sit for two days. After three days, Margot noted that the steel wool pads soaked with water and with vinegar were no longer gray but brownish-orange. Use the information given above and your knowledge of chemical and physical changes and properties of matter to answer the questions that follow.
1. Describe the three systems investigated by the students.
2. What was the purpose of the first set-up containing the steel wool and the thermometer, but no liquid?
3. Classify the glass, steel wool, vinegar, and water as heterogeneous mixtures, homogeneous mixtures, or substances.
4. List the physical and chemical properties of the steel wool pads that were directly observable by the experimenters.
5. What caused the temperature in the steel wool-vinegar system to increase?
6. Describe the reaction that occurred in the steel wool-water system."

Answer 1

The students investigated three systems involving steel wool pads and different substances. The purpose of the first set-up was to establish the initial temperature. The glass is a substance, the steel wool and vinegar are heterogeneous mixtures, and the water is a homogeneous mixture.

Step-by-step explanation:

1. The three systems investigated by the students are:

1. Steel wool pad and thermometer
2. Steel wool pad soaked in water
3. Steel wool pad soaked in vinegar

2. The purpose of the first set-up containing the steel wool and the thermometer, but no liquid, was to establish the initial temperature and observe any changes that occur when the steel wool is soaked in different substances.

3. The glass is a substance, the steel wool and the vinegar are heterogeneous mixtures, and the water is a homogeneous mixture.

4. The physical properties of the steel wool pads that were directly observable by the experimenters are the color, texture, and temperature.

5. The temperature in the steel wool-vinegar system increased because a chemical reaction occurred between the steel wool and the vinegar, releasing energy in the form of heat.

6. In the steel wool-water system, a physical change occurred. The water molecules interacted with the steel wool, causing it to change color and texture, but no chemical reaction took place.