Listening Section 3: Multiple Choice & Matching: Question 7

Transcript-based practice (no audio).

Sofia: Right, we've got all our data from the marble chip experiment, whole chips, halved chips, and powdered, each reacting with the same concentration of hydrochloric acid. Now we actually have to write the thing up before Friday.

Ade: Let's start with how we present the results. I was thinking three separate graphs, one for each chip size, so each one is really clear on its own.

Priya: I don't think that works, actually. If they're separate, nobody can compare the rates directly. We should put all three on one graph: volume of gas against time, with three lines, one per chip size. That way the difference in gradient jumps out immediately.

Sofia: Agreed, one graph's much stronger. We can put the raw data table in an appendix rather than the main body.

Ade: Fine by me. Now, what do we do about that weird result, the powdered chips' reading at ninety seconds? It's way faster than the trend around it.

Priya: We shouldn't just delete it. I think we keep it in the table but add a note in the write-up flagging it as a likely timing or reading error, rather than pretending it didn't happen.

Sofia: Yes, and to be fair, it doesn't actually change our overall conclusion, so there's no reason to hide it.

Ade: Speaking of the conclusion, powdered chips reacted fastest overall, right? Because they expose more surface area to the acid, so the rate increases as surface area increases.

Priya: Exactly, and that's the pattern across all three chip sizes, not just powder versus whole.

Sofia: Okay. What about the method section. How much detail do we need? Dr Okafor's brief just says "describe your method."

Ade: I'd say we need enough that someone else in the class could actually repeat it exactly. Quantities, concentration, how the gas syringe was set up, timing intervals, all of it.

Priya: Definitely not just a list of equipment with no numbers, that's what lost us marks in the first practical. And we can't copy the method sheet Dr Okafor gave us either; that counts as not writing it in our own words.

Sofia: Agreed on both counts. Now, sources of error. Ade, you mentioned timing error before. Anything else?

Ade: Timing's the obvious one, reaction time on the stopwatch. But we should also mention gas escaping before the bung was fully sealed each time, since that would make our rate look slower than it really was.

Priya: Good point, let's include both, not just the timing one.

Sofia: Last thing, the data table. Do we round the times, and where do the units go?

Priya: Round to the nearest whole second. The stopwatch reaction time makes anything more precise misleading. And units go once, in the column heading, not repeated after every single number.

Ade: Agreed. Let's combine our sections into one document and proofread it together Thursday evening, ready before the Friday deadline.

Choose the correct letter, A, B or C.

1. How do they decide to present the gas-volume results? A. Three separate graphs, one for each chip size. B. A single bar chart showing total gas produced after five minutes. C. One graph with three lines, one per chip size, so rates can be compared directly.

2. What do they decide to do with the anomalous fast reading for the powdered chips at ninety seconds? A. Delete it from the results entirely. B. Keep it in the table but flag it as a likely error in the write-up. C. Recalculate it using the average of the surrounding points.

3. According to the discussion, why did the powdered marble chips react fastest overall? A. They expose more surface area to the acid than larger chips. B. They contain a different chemical composition from the whole chips. C. The acid used with them was more concentrated.

4. What level of detail do they agree the method section needs? A. A simple list of equipment, without quantities. B. Enough detail that another student could exactly repeat the experiment. C. A copy of Dr Okafor's original method sheet.

5. What sources of error do they agree to include? A. Timing error only. B. Gas escaping before the bung was sealed only. C. Both timing error and gas escaping before the bung was sealed.

6. What do they decide about how times are recorded in the data table? A. Rounded to the nearest whole second, with units stated once in the column heading. B. Recorded to two decimal places for precision. C. Units written after every individual number in the table.

7. What do they agree to do before submitting the report? A. Submit individual sections separately without combining them. B. Combine their sections into one document and proofread it together on Thursday evening. C. Submit without proofreading, given the Friday deadline.