ACT Science Practice Test 6

A scientist studying hemoglobin investigated the impact of temperature and carbon dioxide (CO₂) concentrations on the binding capacity of oxygen (O₂). The scientist observed the binding of oxygen to hemoglobin molecules as the pressure of oxygen was increased. The temperature and CO₂ were varied to identify their direct impact on the binding capacity of O₂.

Figure 1 displays the impact of changes in temperature on the binding (percent of hemoglobin saturated) of oxygen. Figure 2 displays the impact of varying carbon dioxide concentrations on oxygen binding. Under normal conditions, the core body temperature is 37°C and has carbon dioxide and oxygen concentrations of 40 mmHg and 100 mmHg respectively.

Figure 1

Figure 2

The magnitude of seismic energy released from an earthquake is often described using the logarithmic and unit-less Richter scale. Originating at the epicenter, seismic energy travels through the earth via waves such as L-waves, S-waves, and P-waves. Earthquakes with a Richter scale magnitude of 5.0 or greater can typically be detected throughout the world. Figure 1 depicts the layers of the earth and typical travel patterns of seismic waves. Table 1 lists characteristics of those seismic waves. Figure 2 shows the number of earthquakes (by magnitude) detected at a particular seismic activity monitoring station in the past 30 years, as well as the percentage probability of future earthquakes (by magnitude) in that same region in the next 30 years.

Figure 2

In agriculture, soils can be classified based on mineral content (the amount of various metals present in the soil), and organic content (the percent of soil volume occupied by material made by living organisms). Ideal concentrations of various minerals are given in parts per million (ppm) in Table 1. If the levels of different minerals of a soil are all similar, relative to the optimal levels, the soil is said to be well defined. If the levels of different minerals in a soil vary widely relative to the optimal levels, the soil is said to be poorly defined.

Study 1

Soil was taken from 5 different farms to a laboratory. The soils were desiccated (all water was removed), and a 1 L sample of each soil was prepared. In order to make sure that no minerals were trapped within the organic matter of a soil, the organic matter of each soil was burned by heating the soil to 500°C for 20 minutes. The ash of the organic matter was removed and the remaining soil analyzed for the concentration of various minerals. The results are shown, as percent of ideal concentration, in Table 2.

Study 2

To determine the percentage of the mass of each soil composed of organic matter, the above procedure was repeated, with the soil weighed before being heated to 500°C and after having the ash removed. The number of live cells (bacteria, fungi, etc.) in a cubic millimeter of each soil was determined by microscopic analysis. The results are presented in Table 3.

Rock candy was made by putting a mixture of 180°°F water and an amount of sugar (S1) into an apparatus shown in Figure 1, inserting a string through the top, and allowing the mixture to stand and cool. The internal container was a jar made of glass, and the external container was made of plastic.

Figure 1

Figure 2 shows how the temperature of S1 and the temperature of the cold water in the outer jar varied with time as the mixture was allowed to stand.

Figure 2

According to the Second Law of Thermodynamics, as the temperature of S1 decreases, the orderliness of the atoms in the solution must increase. This is why crystals form on the string, creating rock candy. Because of the Second Law of Thermodynamics, temperature of the sugar and water mixture can be monitored to measure orderliness of the atoms in the mixture. Two other sugar and water mixtures (S2 and S3) were monitored under standing conditions the same as those used for S1.

Figure 3