Science practice 57

The melting point of a substance is the temperature at which the solid phase transitions to the liquid phase. When a substance melts, the attractive forces holding the molecules together are reduced sufficiently to allow the molecules to flow. The stronger the intermolecular forces in solid form, the higher the melting point will be.

The boiling point of a substance is the temperature at which the vapor pressure in the liquid phase equals the atmospheric temperature of its surroundings. When a substance boils, the substance transitions from a liquid phase to a gaseous phase and the intermolecular forces are completely severed. The stronger the attractive forces between the molecules in the liquid phase, the higher the boiling point will be.

Table 1 and Figure 1 show details of some of the elements from the third row of the periodic table.

Table 1

Figure 1

From 1971 to 2006, there was a dramatic reduction in the number of feral honeybees in the United States, and a significant, though somewhat gradual, decline in the number of colonies maintained by beekeepers. In early 2007 the rate of attrition reached new proportions, and the term Colony Collapse Disorder (CCD) was coined to describe this sudden decline. CCD is said to have occurred when a bee colony abruptly disappears, with little or no build-up of dead bees in or around the colonies. The cause or causes of the syndrome are not yet well understood. Proposed causes include environmental change-related stress, malnutrition, disease, and pests.

Study 1

In an attempt to quantify the degree and extent of losses experienced in the United States, scientists tracked beekeeping operations with various numbers of colonies between September 2006 and March 2007. For the sake of this study, a colony has encountered CCD when it loses at least 90% of its population in a period of 30 days. This loss must be accompanied by little or no trace of dead bees in or around the hive. Figure 1 displays the total losses experienced by all beekeeping operations.

Figure 1

Study 2

Scientists studying CCD surveyed beekeepers whose hives have been affected by the disorder. The beekeepers were asked what they believe caused the CCD in their colonies. Table 1 displays the five most commonly suspected causes of CCD losses and the average percentage of loss experienced by operations of varying sizes due to each suspected cause. The scientists then surveyed beekeepers whose hives had collapsed for reasons unrelated to CCD, asking them the same question. Figure 2 compares the results from the scientists’ two surveys, displaying the total loss experienced due to suspected causes of CCD and non-CCD losses, averaged for operations of all sizes.

Table 1

Figure 2