The termite Reticulitermes flavipes consumes wood and bark. A study examined whether the consumption of wood or bark mulch by R. flavipes varies with the type of mulch or the age of the mulch. Separate portions of each of 5 types of mulch were aged (allowed to decay) for 1, 24, and 48 weeks. Then, 2 g of each type of 1-week-old mulch were put into a box, 2 g of each type of 24-week-old mulch were put into a second box, and 2 g of each type of 48-week-old mulch were put into a third box. Next, 1 g of R. flavipes was added to each box. After 15 days, the mass of mulch consumed, in milligrams (mg), was determined for each type and age of mulch (see figure).

Samples of Species C bacteria must often be trans- ported from the areas in which they are collected. During transport, the samples are typically packed in ice to keep them alive. However, ice is not always available where the samples are collected.

Scientists studied how lyophilization (a freeze-drying process that doesn't require ice) followed by incubation affects the survival of 2 strains (Strain E and Strain V2) of Species C bacteria.

Experiment 1

The scientists placed a 100 µL (1 µL = 10 mL) sample of a nutrient medium containing 4x 10° Strain E elementary bodies into each of 8 sterile test tubes. An elementary body is the infective form of Species C. The sample in each of the tubes was then lyophilized, and each tube was sealed. Two of the tubes were incubated at 4°C, 2 were incubated at 20°C, 2 were incubated at 30°C, and 2 were incubated at 37°C.

One week after the start of incubation, the percent survival (the percent of the elementary bodies that survived) was determined for the sample in I of the 2 tubes at each temperature. Then, 1 month after the start of incubation, the percent survival was determined for the sample in the remaining tube at each temperature. The results are shown in Table 1.

Experiment 2

The scientists repeated Experiment 1. except with Strain V2 instead of Strain E. The results are shown in Table 2.

When an object is submerged in a fluid, the object dis- places a volume of fluid equal to the object's submerged volume. The fluid exerts an upward buoyant force on the object that is equal in magnitude to the weight of the dis- placed fluid. The object floats if the buoyant force equals the object's weight.

A group of students conducted 2 studies on buoyant forces using 3 fluids-water, Fluid A, and Fluid B- having densities of 1.0 g/cm³, 1.25 g/cm³, and 1.50 g/cm³. respectively.

Study 1

The students placed a 10 cm long cylinder in a container of water and measured the length of the portion of the cylinder that was submerged. They then repeated this procedure with a container of Fluid A and a container of Fluid B (see Figure 1).

Study 2

The students placed a stone either Stone X, Stone Y, or Stone Z-in a net that was tied to a spring balance. They recorded the force measured by the balance as the stone's weight, W. They then submerged the stone in water and again recorded the force measured by the balance (see Figure 2).

The students calculated the buoyant force on the stone in water as W minus the force that was measured when the stone was submerged. They repeated this procedure to test all 3 stones in all 3 fluids. Table 1 lists each stone's volume, in cm³, and W, in newtons (N), as well as the buoyant force, in N, on each stone in the fluid.

Chemical reactions that release heat are exothermic reactions. The amount of heat released depends on the number of moles of reactants consumed in the reaction. A mole of any substance is 6x 10 molecules or formula units of the substance.

When sodium hypochlorite (NaCIO) and sodium iodide (Nal) are dissolved in acidic H₂O, an exothermic reaction occurs:

NaCIO + Nal products + heat

Students did an experiment to study this reaction.

Experiment

In each of 8 trials, the students performed Steps 1-5:

1. A known volume of a 0.2 mole/L aqueous NaCIO solution was poured into a foam coffee cup. A lid was placed on the cup.

2. A thermometer was placed into the solution through a hole in the lid. The solution's initial temperature, T., of 22.0°C was recorded.

3. The lid was lifted, and a known volume of a 0.2 mole/L aqueous Nal solution, also at a
TI of 22.0°C, was poured into the cup. The lid was put back on the cup, and the solution was swirled.

4. The solution's final (maximum) temperature, TF was measured.

5. The change in temperature, ΔT, was calculated:

ΔT= Tf-TI

The data for each trial are shown in Table 1.

Then they identified the trial for which AT had its greatest value. The ratio of the volume of the NaCIO solution to the volume of the Nal solution for this trial is the mole ratio for the reaction.

When rocks are melted at very high temperatures beneath Earth's surface, magma (molten rock) is formed. The gases CO, and H₂O can dissolve in magma. Figure 1 shows, for 4 different magmas (leucitite, basanite, rhyolite, and tholeiitic basalt), how the solubility of CO₂ in the magma at 1,150°C varies with pressure (in megapascals, MPa).