Table 6 Students’ performances in understanding of “the properties and transformation of substances”
From: A case study of student development across project-based learning units in middle school chemistry
Units | Performances | Levels |
|---|---|---|
Unit 4 Low-Carbon Action | [Classroom observations] S: Our group’s low-carbon convention was about why adjusting the air-conditioning temperature can reduce carbon dioxide production. Adjusting the air-conditioning temperature reduces electricity generation. The power supply mode in China is thermal power generation, and many combustibles contain carbon. According to the conservation of elements, these combustibles will be converted into carbon dioxide after combustion. Therefore, adjusting the air-conditioning temperature to be moderate (not too low or too high) can reduce the generation of carbon dioxide. [Focus group interviews] S: Before class, I only knew that we should drive less, but I did not know why. Now, I know we can use carbon dioxide production and conversion to achieve low carbon emissions. | Level 3: Application |
Unit 5 Reasonable Use of Metal Products | [Classroom observations] S: The outer shell and inner layer of the thermos cup we chose are made of food-grade pp. material. The innermost layer is made of stainless steel, which was chosen because of its strong thermal conductivity, high temperature resistance, and corrosion resistance. The bottom of the cup is surrounded by rubber, and the body is frosted, which makes it is easy to carry and resistant to falls. However, we cannot use steel wire balls to clean the thermos cup because they can damage its inner container. The thermos cup cannot be used to hold carbonated beverages, because stainless steel releases heavy metal ions in the presence of acid, which affects an individual’s health. | Level 4: Analysis |
Unit 7 Soil Improvement | [Classroom observations] S: The topic of our research was “the effect of nitrogen fertilizer on the same plants”. The experimental instruments we used were four pots with the same green cirrus, a balanced and nitrogen fertilizer, sodium carbonate, soil and water. The research methods we used were comparison, experiment and observation. Our experimental process was divided into five steps: (1) We collected soil samples from the park, mixed them with water, and measured their acidity and alkalinity with pH test paper. We found that the acidity and alkalinity of the soil samples did not meet the conditions for the growth of green cirrus. (2) We added large amounts of water to the soil, but we could not obtain a suitable pH value. Finally, we chose to mix a small amount of sodium carbonate with the water, because this solution is alkaline, which can be neutralized by the soil so it reaches a suitable pH value for plants. (3) Next, we prepared four identical green cirrus plants, which were placed in flowerpots with holes at the bottom. The prepared soil (all with the same quality and pH value) and 5 g, 10 g and 15 g of nitrogen fertilizer measured by a balance in advance were added into three flowerpots, while we did not add any fertilizer to the fourth pot. Then, we watered the plants on time. (4) We placed the four pots of green cirrus in a warm and sunny environment to ensure they are in the same growth environment. (5) We observed and compared the growth of the four pots of green cirrus and recorded them in real time. …… | Level 5: Synthesis |