ACT Science Practice Test 41

Two experiments were performed to study Newton’s laws of motion using air track gliders. The friction between the gliders and the air track is nearly zero. Each glider has a spring attached on each end.

Experiment 1

Two identical gliders were placed on an air track as shown in Figure 1. The gliders’ springs were then compressed completely together along with the gliders and released. When the gliders were pushed apart by their springs, the data in Table 1 was recorded. The zero position was recorded as the far-left point where Glider 1 is shown in Figure 1.

Table 1

Figure 1

Experiment 2

The same experiment was performed but Glider 3 was a double-weight glider in the first trial. In the second trial, Glider 4, a triple-weight glider, was tested.

Table 2

The velocity for each trial was calculated and the ratio of Glider 1 to the other glider was graphed and shown in Figure 2.

Figure 2

Since carbon is essential to life on Earth, understanding the global carbon cycle can provide valuable information. Through the process of photosynthesis, plants on land or algae living in water convert carbon dioxide into organic products. Through the process of respiration, organisms convert these organic compounds into energy and release carbon dioxide. Figure 1 displays the global carbon cycle.

Figure 1

A significant amount of carbon is released through the burning of fossil fuels. Some of this carbon is stored in the atmosphere, while a significant portion is stored in ocean waters and sediments. Carbon in the ocean is described as dissolved inorganic carbon, particulate inorganic carbon, particulate organic carbon (POC), and dissolved organic carbon (DOC). Particulates are defined as those larger than 0.2 micrometers, whereas dissolved matter is that smaller than 0.2 micrometers (see Figure 2).

Figure 2

Chromophoric dissolved organic matter (CDOM) is the colored portion of DOC. It is colored because it intensely absorbs violet and blue light. Figure 3 displays DOC and CDOM absorption in the tropical North Atlantic Ocean.

Figure 3

Three substances have been shown to inhibit respiration in various organisms: hydrocyanic acid, hydrogen sulfide, and carbon monoxide. An experiment was conducted to determine the effect that each of these substances has on the respiration of the green alga Chlorella. Figure 1 shows the results.

Figure 1

Researcher 1 argued that glucose would have a contradictory effect on the alga, so that if the Chlorella were suspended in a solution containing 1 percent glucose, there would be less of an effect on respiration. Figure 2 displays the results of the experiment.

Figure 2

Researcher 2 hypothesized that light may play an active part in respiration of Chlorella, so an experiment was done to measure the effect of successive periods of light and darkness on the respiration of cells suspended in carbon monoxide and in nitrogen. The results are shown in Figure 3.

Figure 3

A catalyst is a substance that speeds up a reaction, but is chemically unchanged at the end of the reaction. Catalysts can be divided into two main types—heterogeneous and homogeneous. In a heterogeneous reaction, the catalyst is in a different phase (such as solid, liquid, or gas) from the reactants. In a homogeneous reaction, the catalyst is in the same phase as the reactants. Most examples of heterogeneous catalysis go through the same stages (see Table 1).

Table 1

Students did experiments to convert propanol to propene using alumina beads, and then to convert propene to propanol using a palladium catalyst.

Experiment 1

Two glass syringes were connected to an aluminabead catalyst tube (see Figure 1). The 1 mL syringe was filled with 1 mL of propanol. Next, the apparatus was held above a burner’s flame and the alumina-bead catalyst tube was gently heated while the liquid propanol was slowly introduced into the catalyst tube. The liquid flowed through the tube until it hit the hot region. Then it vaporized, reacted with the catalyst, and exited the catalyst tube as gaseous propene into the 60-mL receiver syringe. The procedure was repeated with various amounts of propanol and alumina beads and the amount of gaseous propene collected was recorded (see Table 2).

Figure 1

Table 2

Experiment 2

A reactant syringe was filled with equal volumes of hydrogen and propene. The reactant syringe and receiver syringe were connected to the catalyst tube filled with solid palladium as shown in Figure 2. Then the hydrogenpropene mixture was slowly passed over the catalyst, the reaction occurred, and the propane was collected in the receiver syringe. The procedure was repeated several times, varying the amount of time the reactant was passed over the catalyst. The results are shown in Table 3.

Figure 2

Table 3