Two chemicals at room temperature (about 23°C) were combined in a flask. At first, there were bubbles. Then, white flakes appeared at the bottom of the flask. After five minutes, the temperature of the solution was 33°C. A portion of the solution was used to measure its density and boiling point, which were determined to be 4.5 g/L and 82°C, respectively.
Did a physical or chemical change occur?
How do you know it is not the other kind of change? Provide at least three points of evidence that support your claim.
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To determine whether a physical or chemical change occurred in this scenario, we need to analyze the given information and look for evidence that indicates the nature of the change. Here are three points of evidence that can support our claim:
1. Formation of white flakes: The appearance of white flakes at the bottom of the flask suggests the formation of a solid substance. In a chemical change, new substances are formed with different chemical properties than the original ones. The formation of a new solid substance indicates a chemical change rather than a physical change, where the composition of the substances usually remains the same.
2. Change in temperature: The temperature of the solution increased from 23°C to 33°C after five minutes. A change in temperature could be an indication of a chemical reaction. During a chemical change, energy is often absorbed or released, which can lead to a temperature change. In physical changes, such as change in state (e.g., melting, boiling), the temperature remains constant until the change is complete.
3. Changes in density and boiling point: The density and boiling point of the solution were determined to be 4.5 g/L and 82°C, respectively. Changes in physical properties such as density and boiling point may suggest a chemical change. During a chemical reaction, the composition and arrangement of atoms/compounds can change, leading to alterations in physical properties. In physical changes, these properties typically do not change significantly, or they change due to external factors like pressure or temperature.
Based on these points of evidence, it is likely that a chemical change occurred in this scenario. The formation of white flakes, change in temperature, and changes in density and boiling point all align with typical indicators of a chemical reaction rather than a physical change.