Classifying the physical composition of matter (pure substance vs. homogeneous vs. heterogeneous mixture) was the most difficult aspect, and confusion between homogeneous and heterogeneous mixtures persisted after instruction¶

Claim · All claims
Evidence · 1 study (2 entries) · causal r1 · q2
Currency · newest study 2013 · not yet checked against its sources · not reviewed by a person · overdue for a recheck since 2018: baselines and conditions change

Subclaims¶

q2 i? Inappropriate classifications of physical composition were numerous at pretest (n=45), decreased to n=34 at posttest, but increased again to n=40 at delayed posttest. → Yakmaci-Guzel 2013 q2 i? Many participants misclassified homogeneous mixtures as heterogeneous mixtures, citing "more than one type of elements or compounds" and irregular particle distribution. → Yakmaci-Guzel 2013 (2)

Evidence¶

Yakmaci-Guzel 2013¶

Yakmaci-Guzel, B., & Adadan, E. (2013). Use of multiple representations in developing preservice chemistry teachers' understanding of the structure of matter. International Journal of Environmental & Science Education, 8(1), 109-130. https://eric.ed.gov/?id=EJ1008597

q2 · i? · causal · r1

Frequency counts across the three testing instances (Table 7) in the same one-group study show physical composition was "the most difficult task for the participants in all three data collection instances".

"there were numerous scientifically inappropriate classifications of the physical composition of matter on the pretest (n=45) (see Table 7). Following the instruction, the number of inappropriate classification cases considerably decreased (n=34), but on the delayed posttest, the participants' scientifically inappropriate classification of the particulate representations increased again (n=40)"

Yakmaci-Guzel 2013 (2)¶

Yakmaci-Guzel, B., & Adadan, E. (2013). Use of multiple representations in developing preservice chemistry teachers' understanding of the structure of matter. International Journal of Environmental & Science Education, 8(1), 109-130. https://eric.ed.gov/?id=EJ1008597

q2 · i? · causal · r1

Analysis of written justifications on the pretest: 15 of 19 participants misclassified Picture 4 and 12 of 19 misclassified Picture 2 as heterogeneous mixtures when both represented homogeneous mixtures, paralleling Sanger's (2000) findings.

"The participants who classified homogenous mixtures as heterogeneous mixtures (Picture 2 and 4) generally indicated in their written justifications that these pictures had "more than one type of elements or compounds" and also they had an "irregular (or unequal) distribution of particles.""

Discussion¶

Related Claims¶

• A multiple-representations instruction significantly increased preservice chemistry teachers' scientifically appropriate classifications of particulate drawings from pretest to posttest — a broader claim this one bears on
• Improvements in classifying the chemical composition of matter were not durable: some participants reverted to their initial inappropriate classifications 17 months later — related
• The instruction was most effective for the physical states of matter, shifting justifications from macroscopic to submicroscopic evidence — related