Question

A solid white substance \(A\) is heated strongly in the absence of air. It decomposes to form a new white substance \(B\) and a gas \(C\). The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. Based on these observations, can we determine whether solids \(\mathrm{A}\) and \(\mathrm{B}\) and the gas \(\mathrm{C}\) are elements or compounds? Explain your conclusions for each substance.

Short answer

Based on the given information and analysis, we can conclude that substance A and substance B are likely compounds, as substance A decomposes into two different substances and substance B is formed from the decomposition of substance A. Gas C is also a compound, specifically carbon dioxide, as it has the same properties as the product obtained when carbon is burned in excess oxygen. Further information or experiments may be required to confirm the nature of these substances.

Step-by-step solution

Analyze the Formation of Substance B

When solid substance A is heated strongly in the absence of air, it decomposes to form a new solid white substance B and a gas C. This reaction can be represented as: \(A \rightarrow B + C\) Since substance A decomposes into two different substances (substance B and gas C), it indicates that substance A is likely a compound rather than an element. Elements usually don't decompose into different substances.

Analyze Gas C Properties

We know that gas C has the same properties as the product obtained when carbon is burned in an excess of oxygen. When carbon burns in excess oxygen, carbon dioxide (CO2) is produced. Since gas C has the same properties as CO2, we can conclude that gas C is also carbon dioxide. According to this information, we can understand that gas C is a compound since it is made up of carbon and oxygen atoms.

Analyze the Formation of Substance B

We have concluded that substance A is a compound and gas C is carbon dioxide. Based on the given reaction, we know that compound A is decomposed into substance B and gas C when heated. It means that substance B would be what is left after the release of carbon dioxide from substance A. Since the information provided for substance B is limited and it is formed due to the decomposition of a compound (substance A), we can speculate that substance B is also a compound.

Conclusion

Based on the given information and our analysis, we can determine the following for each substance: 1. Substance A is a compound because it decomposes into two different substances. 2. Gas C is a compound (carbon dioxide) because it has the same properties as the product obtained when carbon is burned in excess oxygen. 3. Substance B is likely a compound because it is formed from the decomposition of a compound (substance A). Keep in mind that the conclusions are based on the given information, and we might need more detailed information or experiments to further confirm the nature of these substances.

Key concepts

Chemical Compounds

Chemical compounds are substances composed of two or more different types of atoms bonded together in fixed proportions. These bonds can come in different forms, such as ionic or covalent. Understanding the nature of compounds is foundational in chemistry. For instance, in the provided exercise, solid white substance A decomposes into substance B and gas C, indicating that A is a compound. This is because elements, which are pure chemical substances consisting of a single type of atom, do not break down into other substances under normal circumstances. Compounds, however, can. This distinction between elements and compounds is crucial for students to grasp in order to understand chemical reactions and properties.

Moreover, the decomposed parts of a compound (e.g., B and C) can be other compounds, elements, or a combination of both. Substance B and gas C are likely compounds themselves, given that they arose from the decomposition of compound A, which is a process that often results in the formation of new compounds.

Carbon Dioxide Properties

Carbon dioxide, or CO2, is a colorless gas under standard conditions and well-known for its role in the carbon cycle and as a greenhouse gas in Earth's atmosphere. It consists of one carbon atom covalently bonded to two oxygen atoms. Its properties are central to many chemical reactions and are key to identifying the gas in our exercise.

In the step by step analysis of gas C, knowing that it has the same properties as carbon dioxide allows us to infer its identity. Properties such as density, reactivity, and the ability to extinguish flames all characterize carbon dioxide. Gas C's identity as carbon dioxide reveals that the original compound A contained carbon and oxygen elements. When teaching students about CO2, emphasizing its properties helps them to connect theoretical knowledge with practical applications and real-world phenomena such as the greenhouse effect.

Decomposition Reaction

A decomposition reaction is a type of chemical reaction where one compound breaks down into two or more substances, which could be elements or simpler compounds. There are various types of decomposition reactions, and they can be induced by heat, light, or electricity. In the context of our exercise, the heating of solid white substance A and its transformation into substance B and gas C is a classic example of a thermal decomposition reaction.

Understanding decomposition reactions is vital for students because they illustrate the principle of chemical change and are involved in a plethora of industrial and biological processes. For instance, the breakdown of calcium carbonate to form calcium oxide and carbon dioxide is a common decomposition reaction used to create quicklime. Relating these concepts to real-life examples can help students better understand the relevance and application of chemical reactions in their daily lives.