All ACT Science Resources
Example Questions
Example Question #5 : Chemistry
Chemists can model how solids, liquids, and gases behave at different temperatures and pressures with a graph called a phase diagram. When the pressure and temperature are simultaneously known, a scientist can predict whether the material will be in a specific state. The diagram is divided into sections depending on the phase and the lines between sections represent phase transitions occurring between two or more separate phases.
In general, solids of neatly stacked molecules exist when temperatures are low and pressures are intermediate. These values decrease the kinetic energy of the molecules enough to allow for attractive forces to begin the stacking process. Liquids, by contrast, are found at intermediate pressures and temperatures. The temperature is high enough to impart enough kinetic energy to prevent solid formation and the pressure is high enough to prevent the liquid from becoming a gas. Finally, a gas forms at low pressures and high temperatures. The high level of kinetic energy prevents molecules from associating with one another.
Materials can undergo processes called phase transitions, meaning they can transition from one phase to another. The transition from a solid to a liquid is called melting, while the reverse transition is called freezing. Vaporization occurs when a liquid becomes a gas, while condensation occurs when a gas becomes a liquid. Finally, in a process called sublimation, a solid can directly become a gas without passing through a liquid phase. Additionally, when a gas directly becomes a solid, this is known as deposition.
According to the figure, the material represented by Area 1 is in what phase?
Solid
Gas
Cannot Be Determined
Liquid
Solid
According to paragraph two, solids are sets of neatly stacked molecules and exist when temperatures are low and pressures are intermediate. Looking at our figure, we can see that at low temperatures (towards the origin) and intermediate pressures, we are looking at area one. Thus, area one must be in the solid phase.
Example Question #7 : Chemistry
Chemists can model how solids, liquids, and gases behave at different temperatures and pressures with a graph called a phase diagram. When the pressure and temperature are simultaneously known, a scientist can predict whether the material will be in a specific state. The diagram is divided into sections depending on the phase and the lines between sections represent phase transitions occurring between two or more separate phases.
In general, solids of neatly stacked molecules exist when temperatures are low and pressures are intermediate. These values decrease the kinetic energy of the molecules enough to allow for attractive forces to begin the stacking process. Liquids, by contrast, are found at intermediate pressures and temperatures. The temperature is high enough to impart enough kinetic energy to prevent solid formation and the pressure is high enough to prevent the liquid from becoming a gas. Finally, a gas forms at low pressures and high temperatures. The high level of kinetic energy prevents molecules from associating with one another.
Materials can undergo processes called phase transitions, meaning they can transition from one phase to another. The transition from a solid to a liquid is called melting, while the reverse transition is called freezing. Vaporization occurs when a liquid becomes a gas, while condensation occurs when a gas becomes a liquid. Finally, in a process called sublimation, a solid can directly become a gas without passing through a liquid phase. Additionally, when a gas directly becomes a solid, this is known as deposition.
According to the figure, the material represented by area two is in what phase?
Cannot Be Determined
Gas
Solid
Liquid
Liquid
According to paragraph two, liquids are found at intermediate pressures and temperatures. The only section on the graph that corresponds to intermediate pressures and temperatures is area two.
Example Question #6 : Chemistry
Chemists can model how solids, liquids, and gases behave at different temperatures and pressures with a graph called a phase diagram. When the pressure and temperature are simultaneously known, a scientist can predict whether the material will be in a specific state. The diagram is divided into sections depending on the phase and the lines between sections represent phase transitions occurring between two or more separate phases.
In general, solids of neatly stacked molecules exist when temperatures are low and pressures are intermediate. These values decrease the kinetic energy of the molecules enough to allow for attractive forces to begin the stacking process. Liquids, by contrast, are found at intermediate pressures and temperatures. The temperature is high enough to impart enough kinetic energy to prevent solid formation and the pressure is high enough to prevent the liquid from becoming a gas. Finally, a gas forms at low pressures and high temperatures. The high level of kinetic energy prevents molecules from associating with one another.
Materials can undergo processes called phase transitions, meaning they can transition from one phase to another. The transition from a solid to a liquid is called melting, while the reverse transition is called freezing. Vaporization occurs when a liquid becomes a gas, while condensation occurs when a gas becomes a liquid. Finally, in a process called sublimation, a solid can directly become a gas without passing through a liquid phase. Additionally, when a gas directly becomes a solid, this is known as deposition.
According to the figure, the material represented by area three is in what phase?
Solid
Liquid
Gas
Cannot Be Determined
Gas
According to paragraph two, gas exists at low pressures and high temperatures. Looking for area three on the figure, we see that this region corresponds to low pressures and high temperatures and thus must represent the gaseous state.
Example Question #691 : Act Science
The Ideal Gas Law is as follows:
is pressure as measured in Pascals, is volume as measured in cubic meters, is the number of moles of the gas, is the gas constant known as 8.314 Joules per mole times Kelvin, and is the temperature measured in Kelvin.
A class of students began studying the Ideal Gas Law and how the Pressure and the Volume relate to one another. They took 20 moles of a sample gas and kept the room at a temperature of 300 Kelvin. They then used different sized containers of the gas to limit and expand the volume. At each different volume, they measure the pressure of the gas on its container. The table they made from their results is seen in table 1.
Temperature in Kelvin |
Pressure Measured in Pascals |
|
|
200 Kelvin |
16, 628 Pascals |
400 Kelvin |
33, 256 Pascals |
600 Kelvin |
49, 884 Pascals |
800 Kelvin |
66, 512 Pascals |
TABLE 1
FIGURE 1
The graph the students made based on the data is seen in Figure 1.
Pressure is created by the movement of the gas molecules pushing against a container. 0 Kelvin is known as absolute 0, the temperature at which all molecule movement theoretically stops.
Describe the relationship between the temperature and the pressure.
They are inversely related. As temperature decreases, pressure increases.
The relationship cannot be determined from the graph.
They are directly related. As temperature increases, so does pressure.
The pressure remains the same no matter the temperature.
They are unrelated.
They are directly related. As temperature increases, so does pressure.
For every increase in temperature, there is a definite increase in pressure that can be found in the Ideal Gas Law equation. When the equation is solved for pressure
it can be thought of as the slope-intercept form of a line, with the y-intercept as 0 and the as the slope in front of the -coordinate, which in this case is temperature.
Example Question #12 : Chemistry
The Millikin oil drop experiment is among the most important experiments in the history of science. It was used to determine one of the fundamental constants of the universe, the charge on the electron. For his work, Robert Millikin won the Nobel Prize in Physics in 1923.
Millikin used an experimental setup as follows in Figure 1. He opened a chamber of oil into an adjacent uniform electric field. The oil droplets sank into the electric field once the trap door opened, but were then immediately suspended by the forces of electricity present in the field.
Figure 1:
By determining how much force was needed to exactly counteract the gravity pulling the oil droplet down, Millikin was able to determine the force of electricity. This is depicted in Figure 2.
Using this information, he was able to calculate the exact charge on an electron. By changing some conditions, such as creating a vacuum in the apparatus, the experiment can be modified.
Figure 2:
When the drop is suspended perfectly, the total forces up equal the total forces down. Because Millikin knew the electric field in the apparatus, the force of air resistance, the mass of the drop, and the acceleration due to gravity, he was able to solve the following equation:
Table 1 summarizes the electric charge found on oil drops in suspension. Millikin correctly concluded that the calculated charges must all be multiples of the fundamental charge of the electron. A hypothetical oil drop contains some net charge due to lost electrons, and this net charge cannot be smaller than the charge on a single electron.
Table 1:
Trial # |
Electric Charge Calculated in Coulombs (C) |
Vacuum Used? |
1 |
1.602176487 x 10-8 |
No |
2 |
1.602176487 x 10-2 |
Yes |
3 |
1.602176487 x 10-6 |
No |
4 |
1.602176487 x 10-4 |
Yes |
Based on Figure 2, an increase on the mass of an oil drop being studied would ______ the acceleration due to gravity?
Initially decrease, then increase
Initially increase, then decrease
Not change
Decrease
Increase
Not change
The acceleration due to gravity and the mass are two distinct variables in the equation presented in Figure 2. Increasing the mass would increase the overall force in the downward direction, but would not increase the acceleration due to gravity.
Example Question #12 : Chemistry
Current high levels of fossil fuel use, including coal-burning power plants and gasoline-powered automobiles, have helped contribute to the high concentrations of sulfur trioxide, SO3, found in the atmosphere. When sulfur trioxide and water interact, they can undergo the following chemical reaction to produce sulfuric acid, which is the main contributor to acid rain worldwide:
Acid rain showers are particularly common near coal-burning power plants and large cities. These showers are responsible for significant economic damage to sidewalks, roads, and buildings. Scientists interested in studying the effects of acid rain often use basic substances like calcium carbonate, the main component of limestone buildings, and expose them to varying volumes of acid rain to determine what volume of acid rain is necessary to begin to erode a building. A sample graph of one scientist’s experiment is replicated below:
Measuring acid and base levels is commonly done with a scale called pH, which uses the concentration of hydrogen ions to determine the acidity. Hydrogen ions are in a balance with hydroxide ions to give a scale with a range from 0 to 14. Values equal to or between 0 and 6.9 represent the acidic range where hydrogen ions predominate and values equal to or ranging from 7.1 and 14 represent the basic range where hydroxide ions predominate. Thus, the more hydrogen ions present, the more acidic the solution.
Scientists can tell when a titration (pH) experiment passes a certain pH using compounds called indicators. Indicators are usually colorless at pH levels below that of their specified color change. A table of indicators used by the above scientists and the pH at which they change colors is presented below.
What is the pH of a solution containing calcium carbonate and sulfuric acid when 20 mL of sulfuric acid have been added?
7
12
10
2
7
This question asks us to use the provided figure to determine the average pH of a solution in the titration explained in the passage. We can see that when 20 mL of sulfuric acid have been added to the calcium carbonate solution, the resulting pH falls in the middle of the sigmoidal curve at a pH of around 7. These problems are important to understand because the ACT tends to test the interpretation of figures and charts heavily.
Example Question #692 : Act Science
Current high levels of fossil fuel use, including coal-burning power plants and gasoline-powered automobiles, have helped contribute to the high concentrations of sulfur trioxide, SO3, found in the atmosphere. When sulfur trioxide and water interact, they can undergo the following chemical reaction to produce sulfuric acid, which is the main contributor to acid rain worldwide:
Acid rain showers are particularly common near coal-burning power plants and large cities. These showers are responsible for significant economic damage to sidewalks, roads, and buildings. Scientists interested in studying the effects of acid rain often use basic substances like calcium carbonate, the main component of limestone buildings, and expose them to varying volumes of acid rain to determine what volume of acid rain is necessary to begin to erode a building. A sample graph of one scientist’s experiment is replicated below:
Measuring acid and base levels is commonly done with a scale called pH, which uses the concentration of hydrogen ions to determine the acidity. Hydrogen ions are in a balance with hydroxide ions to give a scale with a range from 0 to 14. Values equal to or between 0 and 6.9 represent the acidic range where hydrogen ions predominate and values equal to or ranging from 7.1 and 14 represent the basic range where hydroxide ions predominate. Thus, the more hydrogen ions present, the more acidic the solution.
Scientists can tell when a titration (pH) experiment passes a certain pH using compounds called indicators. Indicators are usually colorless at pH levels below that of their specified color change. A table of indicators used by the above scientists and the pH at which they change colors is presented below.
What is the pH of a solution containing calcium carbonate and sulfuric acid when 29 mL of sulfuric acid have been added?
3
7
0
12
0
In this question, we are asked to determine the relationship between pH and volume of sulfuric acid added to the basic solution. This is best done by using the graph provided in the passage. We can see that, as we add more sulfuric acid, the pH of the solution decreases. Around an addition of 30 mL, we can see that the pH of the solution is beginning to approach 0. Given the range of answer choices provided, we can estimate that addition of 29 mL would give a pH of around 0.
Example Question #693 : Act Science
Current high levels of fossil fuel use, including coal-burning power plants and gasoline-powered automobiles, have helped contribute to the high concentrations of sulfur trioxide, SO3, found in the atmosphere. When sulfur trioxide and water interact, they can undergo the following chemical reaction to produce sulfuric acid, which is the main contributor to acid rain worldwide:
Acid rain showers are particularly common near coal-burning power plants and large cities. These showers are responsible for significant economic damage to sidewalks, roads, and buildings. Scientists interested in studying the effects of acid rain often use basic substances like calcium carbonate, the main component of limestone buildings, and expose them to varying volumes of acid rain to determine what volume of acid rain is necessary to begin to erode a building. A sample graph of one scientist’s experiment is replicated below:
Measuring acid and base levels is commonly done with a scale called pH, which uses the concentration of hydrogen ions to determine the acidity. Hydrogen ions are in a balance with hydroxide ions to give a scale with a range from 0 to 14. Values equal to or between 0 and 6.9 represent the acidic range where hydrogen ions predominate and values equal to or ranging from 7.1 and 14 represent the basic range where hydroxide ions predominate. Thus, the more hydrogen ions present, the more acidic the solution.
Scientists can tell when a titration (pH) experiment passes a certain pH using compounds called indicators. Indicators are usually colorless at pH levels below that of their specified color change. A table of indicators used by the above scientists and the pH at which they change colors is presented below.
The relationship between pH and volume of acid added can best be described as which of the following?
Inversely Proportional
Indirectly Proportional
Sigmoidal (S-shaped)
Directly Proportional
Sigmoidal (S-shaped)
In general, the ACT asks students to identify four different types of graphs - directly proportional, inversely proportional, indirectly proportional, and sigmoidal. As the name implies sigmoidal graphs have an "S" shape. Directly proportional graphs are presented as a positive-slope straight line, while the opposite is true for inversely proportional. Indirectly proportional graphs do not present the relationship between two variables as a straight line. Instead the line may be exponential or logarithmic.
Example Question #694 : Act Science
Current high levels of fossil fuel use, including coal-burning power plants and gasoline-powered automobiles, have helped contribute to the high concentrations of sulfur trioxide, SO3, found in the atmosphere. When sulfur trioxide and water interact, they can undergo the following chemical reaction to produce sulfuric acid, which is the main contributor to acid rain worldwide:
Acid rain showers are particularly common near coal-burning power plants and large cities. These showers are responsible for significant economic damage to sidewalks, roads, and buildings. Scientists interested in studying the effects of acid rain often use basic substances like calcium carbonate, the main component of limestone buildings, and expose them to varying volumes of acid rain to determine what volume of acid rain is necessary to begin to erode a building. A sample graph of one scientist’s experiment is replicated below:
Measuring acid and base levels is commonly done with a scale called pH, which uses the concentration of hydrogen ions to determine the acidity. Hydrogen ions are in a balance with hydroxide ions to give a scale with a range from 0 to 14. Values equal to or between 0 and 6.9 represent the acidic range where hydrogen ions predominate and values equal to or ranging from 7.1 and 14 represent the basic range where hydroxide ions predominate. Thus, the more hydrogen ions present, the more acidic the solution.
Scientists can tell when a titration (pH) experiment passes a certain pH using compounds called indicators. Indicators are usually colorless at pH levels below that of their specified color change. A table of indicators used by the above scientists and the pH at which they change colors is presented below.
Solutions A, B, and C each contain a different number of hydrogen ions. Solution A has a pH of 6.9, solution B has a pH of 7.3, and solution C has a pH of 1.3. Place the solutions in order of increasing number of hydrogen ions.
B < C < A
A < B < C
C < A < B
B < A < C
B < A < C
The passage describes that pH indicates the relative number of hydrogen ions present in a solution. We know that more ions are present when the pH is the lowest. Thus, using the pH values provided in the question along with the information contained in the passage, we can place the solutions in decending order with respect to their pH, which is equivalent to listing them in increasing hydrogen number.
Example Question #696 : Act Science
During digestion, the energy in food is converted to energy the body can use. Scientists use calorimetry experiments to measure the calories, or energy, provided by food when it is digested or burned.
The relationship used to find the heat transferred energy is given by , where is the mass of the material, is the given specific heat capacity, and is the change in temperature of the material.
In this experiment, food was burned over a Bunsen burner under a can of 200 ml of water. The temperature change of the water and mass change of the food can be used to determine the calories in four different food items.
Table 1 shows the values of the change of mass of the food items, the change in temperature of the water and the energy. Table 2 shows the energy to mass ratio of three of those food items.
Table 1
Roasted Peanut Peanut Cracker Cheese Puff
Water Temp. Initial 23.9 °C 33.2 °C 40.3 °C 53.9 °C
Water Temp. Final 30.0 °C 40.9 °C 55.9 °C 62.8 °C
Food Mass Initial 0.69 g 0.61 g 3.21 g 1.22 g
Food Mass Final 0.38 g 0.21 g 0.91 g 0.48 g
Energy 1.22 Cal 1.54 Cal 3.12 Cal 1.78 Cal
Table 2
Sample Energy to Mass Ratio (Cal/g)
1 1.36
2 3.93
3 2.40
According to information from Tables 1 and 2, order the samples' energy to mass ratios from least to greatest.
Roasted Peanut, Peanut, Cracker, Cheese Puff
Roasted Peanut, Cracker, Cheese Puff, Peanut
Cracker, Roasted Peanut, Cheese Puff, Peanut
Peanut, Roasted Peanut, Cheese Puff, Cracker
Roasted Peanut, Cracker, Cheese Puff, Peanut
The order of "Roasted Peanut, Cracker, Cheese Puff, Peanut" is correct and can be found after estimating the energy of the food sample divided by the difference between the initial and final masses of the samples.