text: The most common method of teaching chemistry is lecture with a laboratory component. Laboratory courses became a central part of the chemistry curriculum towards the end of the 19th century. The German scientist Justus von Liebig plays a major role in shifting the model of lecture with demonstrations to one that includes a laboratory component. Liebig was one of the first chemists to conduct a laboratory and his methodology became widespread in the United States due to the efforts of Eben Horsford and Charles W. Eliot. After working in Liebigs laboratory, Horsford returned to the United States and helped establish the Lawrence Scientific School at Harvard University. The school was modeled after Liebigs methodology and established the first chemistry laboratory course. Two years later, Charles W. Eliot started to volunteer at the laboratory. Eliots interests in the laboratory grew, and he eventually took charge of it. Eliot was later elected as Harvards president in 1869. Eliot also served other powerful roles in education, which allowed him to influence the widespread adoption of laboratory methods. Today, the American Chemical Society on Professional Training requires students to gain 400 hours of laboratory experience, outside of introductory chemistry, to get a bachelors degree. Similarly, the Royal Society of Chemistry requires students to gain 300 hours of laboratory experience to get a bachelors degree.
  However, since the twenty-first century, the role of laboratory courses in the chemistry curriculum has been questioned in major journals. The main argument against laboratory courses is that there is little evidence for their impact on student learning. Researchers are asking questions such as "why do we have laboratory work in the curriculum? What is distinctive about laboratory work that cannot be met elsewhere in the curriculum?" Researchers are asking for evidence that the investment of space, time and resources in chemistry laboratories provides value to student learning.