Hydrogen peroxide breaks down to form water and oxygen gas. Which observation is evidence that a chemical reaction has occurred?
A. Phase changes are observed.
B. The color of the solution remains clear.
C. The temperature of the solution increases.
D. The mass of the solution remains the same.
C. The temperature of the solution increases is evidence that a chemical reaction has occurred. When hydrogen peroxide breaks down to form water and oxygen gas, energy is released in the form of heat, causing the temperature of the solution to increase. This is an indicator that a chemical reaction has occurred. Option A, B, and D do not show any signs of a chemical reaction.
To determine which observation is evidence that a chemical reaction has occurred, we need to understand the characteristics of a chemical reaction. Chemical reactions involve the rearrangement of atoms to form new substances with different properties. These reactions often result in changes in temperature, color, state of matter, and mass.
Let's now analyze each of the given options to see which one aligns with these characteristics:
A. Phase changes are observed: This option refers to changes in the state of matter, such as solid to liquid or liquid to gas. While phase changes can be a sign of a physical change, they are not a conclusive indicator of a chemical reaction.
B. The color of the solution remains clear: If the color of the solution remains clear, it suggests that no significant change has occurred. This observation is more indicative of a physical change rather than a chemical reaction.
C. The temperature of the solution increases: This option represents an important characteristic of a chemical reaction. Many chemical reactions involve the release or absorption of energy in the form of heat. An increase in temperature is often a clear indication of a chemical reaction occurring.
D. The mass of the solution remains the same: While mass conservation is a fundamental principle, it does not provide direct evidence of a chemical reaction. In a chemical reaction, the atoms are rearranged to form new substances, so the mass of the reactants and products may not be the same.
Based on the analysis, the observation that serves as evidence that a chemical reaction has occurred is:
C. The temperature of the solution increases.
It is important to note that other observations, such as the formation of bubbles, changes in smell, or the presence of precipitates, can also provide evidence of a chemical reaction.