Final answer:
The blood sample collected in the glass tube clots over the hour, with the clotting factors causing separation of the solid blood components from the liquid serum, which is then harvested for further testing.
Step-by-step explanation:
When a lab technician collects a blood sample in a glass tube and waits about an hour before harvesting serum, several processes occur. First, the blood naturally starts to clot as the clotting factors initiate the formation of a blood clot. Over the course of the hour, the clotting process separates the solid components of the blood, such as the red blood cells and platelets, from the liquid component, which is the serum. The serum, which does not contain the clotting factors or the cells, remains in a liquid state.
After the clot has fully formed, the technician can then centrifuge the tube if necessary to further separate the serum, allowing for the clear liquid part to be extracted without the cellular components or clotting proteins, ready for biochemical analyses or other medical tests.