In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Given that all of the following are true, which of the following, if found, provides the strongest evidence against Scientist 2's hypothesis?

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Lye (sodium hydroxide) is a base that neutralizes acids. Suppose that lye is added to water in which an iron pipe has been immersed. According to Scientist 2, the pipe's rate of rusting will most likely __________.

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

An iron nail is placed in an unsealed test tube filled with water. No other substances are added to the water. When the nail is removed after an extended period of time, it is covered by rust. According the Scientist 2, the nail most likely rusted because __________.

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Sodium hydroxide (NaOH) is a compound which dissociates into Na⁺ and OH^- ions in solution. Suppose that sodium hydroxide is added to water in which a piece of iron has been immersed. It is then observed that the rate at which rust forms on the iron increases. Scientist 1 would most likely explain this result by saying that __________.

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

According to Scientist 1, which of the following conditions will result in the least rapid formation of rust?

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Given that the explanation of Scientist 2 is correct, which of the following conditions, if any, will result in the formation of rust?

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Bromothymol blue is a pH indicator that is yellow in acidic solutions and blue in basic solutions. When bromothymol blue is added to a solution, it remains blue. A piece of iron is then immersed in this solution. Given that the explanation of Scientist 2 is correct, which of the following is most likely to occur?

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

In an experiment, oxygen is removed from water by boiling the water. This water is then poured into a flask, and a piece of iron is immersed in the water. Excess air is pumped out from the flask and replaced with helium (He). Then the flask is sealed. After an extended period of time, a reddish-orange substance is observed on the surface of the iron.

Given that Scientist 2 is correct, which of the following most likely describes the identity of the reddish-orange substance?

In studying the effects of adding heat to different substances on each substance's temperature, a researcher conducted the following experiment. The researcher added 1,000 Joules of energy by a controlled heat lamp to four different substances. The temperature change in each substance that was caused by the heat was then measured and recorded. The results of this experiment are shown below.

The researcher is aware of a concept called specific heat and knows that lead has a lower specific heat than wood, which has a lower specific heat than cardboard, which has a lower specific heat than styrofoam. Therefore, the researcher has ordered the objects in the table from lowest specific heat (lead) to highest (styrofoam).

According to the data in the table, what is the apparent relationship between specific heat and the amount that an object's temperature changes when a given amount of heat is added?

When describing their behavior, gases are typically treated as "ideal gases" in what is known as the ideal gas law. Two science students describe the ideal gas law in their own terms:

Student 1: The ideal gas law is based on the assumptions that a gas consists of a large number of molecules and that gas molecules take up negligible space in a gas due to their minuscule size in comparison to the space between each gas molecule. Also important is the assumption that all of the forces acting on gas molecules are from collisions with other gas molecules or a container and not from anything else. According to the ideal gas law, all gases behave the same so long as those assumptions hold true. Therefore, if you measure the volume of helium gas at a certain temperature and pressure, an equivalent amount of radon gas (a much heavier gas) at the same conditions will have the same volume.

Student 2: The ideal gas law's primary assumption is that a gas consists of a very large number of particles. For example, even within a single bacteria there can be billions of gas molecules despite the bacteria's very small size. Therefore, in a room full of gas, there are so many particles that their random behavior is, on average, uniform. There are exceptions to the ideal gas law and those are gases with very high inter-molecular forces of attraction (IMFAs). A gas with high IMFA will behave very differently than a gas with a low IMFA. As one could imagine, because a gas with a high IMFA will have molecules that tend to attract each other, that gas will display a lower volume than that which would be predicted by the ideal gas law.

Based on the passage, which of the following statements best describes where Student 1 and Student 2 disagree?