Question

why? working in the science lab can be a lot of fun. mixing random chemicals and burning stuff just to see what happens can be entertaining (and possibly dangerous), but it doesn’t lead to anything helpful to the scientific community. in order to be helpful to the community, a researcher’s work in the lab must be systematic. a researcher usually asks a question and then designs an experiment to investigate that question. in this activity you will identify different types of variables that will help you design controlled experiments. model 1 – alka-seltzer® and vinegar diagram: before (100.0 ml vinegar, 84 kpa room pressure, 23.5 °c temperature, alka-seltzer added), mix (84 kpa room pressure, changing °c temperature, bubbles), after (100.0 ml solution, 84 kpa room pressure, 22.6 °c temperature) 1. briefly describe the reaction illustrated in model 1 in one or more complete sentences. 2. did the room pressure change as the reaction occurred? if yes, was there an increase or decrease? 3. what two pieces of evidence observed during the “mix” phase of the reaction suggest that a chemical change is taking place? 4. did the solution temperature increase or decrease during the reaction?

Explanation:

Question 1

To describe the reaction, we analyze the "Before", "Mix", and "After" phases. Initially, there's 100.0 mL of vinegar at 23.5 °C and 84 kPa. When Alka - Seltzer is added (Mix phase), a reaction occurs with bubbling (gas production), and after the reaction, we have 100.0 mL of solution at 22.6 °C and 84 kPa. So we can summarize the reaction as: Alka - Seltzer is added to 100.0 mL of vinegar (at 23.5 °C and 84 kPa), a reaction occurs with gas (bubbles) being produced, and after the reaction, a 100.0 mL solution is formed with a temperature of 22.6 °C and pressure still at 84 kPa.

We check the pressure values before, during, and after the reaction. The pressure before the reaction is 84 kPa (Room Pressure), during the reaction it is also 84 kPa, and after the reaction, it is still 84 kPa. So we can determine if the pressure changed.

To find evidence of a chemical change, we look for signs like gas production, temperature change, color change, precipitate formation, etc. In the "Mix" phase, we can see bubbling (which indicates gas production) and a change in temperature (the temperature is labeled as "Changing °C" during the mix phase, and we can also see from the before (23.5 °C) and after (22.6 °C) that there is a temperature change). These two observations (gas production and temperature change) suggest a chemical change.

Answer:

Alka - Seltzer is added to 100.0 mL of vinegar (at 23.5 °C and 84 kPa); a reaction occurs with gas (bubbles) production, and after the reaction, a 100.0 mL solution is formed at 22.6 °C and 84 kPa.

Question 2