Evaluating evidence from a historical chemical controversy: A study in a French high school

The findings are presented in two sections. The first section deals with the evaluation of evidence relating to experimentation in science, while the second concerns the evaluation of evidence relating to scientific communication.

As mentioned earlier, all the evidence provided by Scheele, Priestley and Lavoisier in Scene 8 is correct and crucial (Bensaude-Vincent & Van Tiggelen, 2003). And yet, Table 1 shows that only 52% (33/63), 41% (26/63) and 48% (30/63) of the participants considered Evidence A, B and C, provided by Scheele, to be adequate in the controversy, “Who discovered oxygen?”. Scheele’s evidence has to do with the fact that he knew how to prepare the gas (Evidence A), produced the gas before Priestley and Lavoisier (Evidence B), and obtained the air over the next three years in many different ways (Evidence C).

Table 1. Evaluation of evidence relating to experimentation in science (N-C= non-classified answers)

	Experimentation in science
Scheele
A	52% (33)
B	41% (26)
C	48% (30)
N-C	5% (3)
Priestley
D	52% (33)
E	63% (40)
N-C	10% (6)
Lavoisier
F	63% (40)
G	13% (8)
N-C	29% (18)

This paper does not deal with the “use of evidence” but “evidence evaluation”. Nonetheless, the use of evidence depends on evidence evaluation (Jiménez-Aleixandre & Puig, 2012; Pallant & Lee, 2015). In other words, students should evaluate evidence carefully before using it. In this regard, Djerassi and Hoffmann (2001b) consider that there is no right answer to the question, “Who discovered oxygen?”, pointing out that each chemist (Scheele, Priestley and Lavoisier) offers significant evidence. Despite Scheele’s evidence being of significant value, the participants did not assess it, contrary to our expectations. Evidence B is significant in many ways in the controversy and could, for example, serve to prove that Scheele discovered oxygen. 41% (26/63) of the participants evaluated Evidence B in an appropriate manner (Table 1). This implies that the rest of the students (59%; 37/63) did not consider Scheele’s producing of the gas before Priestley and Lavoisier (Evidence B) to be important evidence.

When it comes to Priestley, Scene 8 of the play “Oxygen” (Djerassi & Hoffmann, 2003) recreates two strong pieces of evidence in the controversy, “Who discovered oxygen?”: he prepared the gas in 1774, three years after Scheele (Evidence D), and conducted a suitable chemical experiment to produce that gas (Evidence E). The participants’ responses indicate that 52% (33/63) of them assessed Evidence D as being relevant (Table 1). Similarly, 63% (40/63) of the students recognized the significance of Evidence E.

Lavoisier’s evidence was also evaluated by the students. According to Table 1, more than half of the participants (63%; 40/63) were aware of the importance of the “suit of rubber” (Evidence F), which Lavoisier invented in the eighteenth century to enable him to perform his experiment with greater care and exactitude. By contrast, only 13% (8/63) of the students considered Evidence G to be substantial in this controversy. This evidence confirms that Lavoisier knew—as did Scheele and Priestley—the method for preparing the gas through the decomposition of “mercurius calcinatus” (mercuric oxide, HgO). The results also indicate that 29% (18/63) of the learners did not assess Lavoisier’s evidence (Table 1).

If all the evidence produced by Scheele, Priestley and Lavoisier in Scene 8 is correct and crucial (Bensaude-Vincent & Van Tiggelen, 2003), why is it that none of the evidence was evaluated by all (100%; 63/63) of the participants? The answer to this question is complex because, as the situation reveals, the participants struggled to properly assess evidence from the controversy. This observation expands on the findings of Xiao and Sandoval (2015) and Zoller and Pushkin (2007) regarding students’ difficulty in evaluating evidence from socio-scientific issues and problem-based laboratory practice, respectively.

In this research, the books and papers that scientists publish are assumed to be a crucial part of scientific communication (Nielsen, 2013). In the controversy “Who discovered oxygen?” Scheele, Priestley and Lavoisier all provide decisive evidence of this type (Djerassi & Hoffmann, 2003).
Scheele provides three relevant facts. First, he wrote a book (which remained unpublished until 1777) to communicate his discovery (Evidence H). Second, at the end of 1774, he sent a letter to Lavoisier detailing his experiments (Evidence I). Third, he told Professor Bergman about his discovery, thinking that he would tell others (Evidence J, which is the least reliable). Table 2 shows that Evidence I (49%; 31/63) was more widely evaluated than either Evidence H (37%; 23/63) or Evidence J (19%; 12/63).

Table 2. Evaluation of evidence relating to scientific communication (N-C= non-classified answers)

	Scientific communication
Scheele
H	37% (23)
I	49% (31)
J	19% (12)
N-C	5% (3)
Priestley
K	30% (19)
N-C	70% (44)
Lavoisier
L	6% (4)
N-C	94% (59)

As for Priestley, he conducted his experiment on August 1, 1774. This chemist mentions something that should be understood as evidence relating to scientific communication: in October, he communicated his observations to Lavoisier (Evidence K). The results indicate that 70% (44/63) of the students had difficulty recognizing the relevance of Priestley’s communication. A similar result was obtained with the situation in which Lavoisier was unaware of any letter from Scheele (Evidence L): very few of the students (6%; 4/63) considered this evidence to be decisive (Table 2). Yet, this evidence is undeniably important in the critical examination of “how much Lavoisier depended upon Priestley [and Scheele] for his understanding of oxygen” (Marshall & Marshall, 2005, p. 31).

A more detailed analysis of the results from Table 2 leads to the observation that the most widely evaluated evidence was Scheele’s sending of a letter to Lavoisier in which he details his experiments (Evidence I, 49%; 31/63). By contrast, the fact that Lavoisier was unaware of the existence of a letter from Scheele (Evidence L) obtained the lowest evaluation. Evidence I and L were extremely decisive in that they led to the critical view that either Scheele (Evidence I) or Lavoisier (Evidence L) discovered oxygen. Indeed, both Evidence I and L are correct (Djerassi & Hoffmann, 2001b). However, the results indicate that the participants were not aware of their relevance.

The findings on the evaluation of evidence relating to scientific communication (Table 2) confirm the ongoing challenges of promoting the informed understanding of scientific communication as part of the nature of science. Nielsen (2013) claims that “it entails enabling science learners and teachers to observe scientific communication as an explicit and reflexive goal of science education itself” (p. 2080). More recently, Mercer-Mapstone and Kuchel (2015) declared the need for explicitly enhancing science communication skills. Consequently, the evaluation of evidence relating to scientific communication has the potential to not only help promote critical thinking but also to address the challenges reported by Nielsen (2013) and Mercer-Mapstone and Kuchel (2015).