Which of the following is a reliable way to observe that a chemical change has occurred when two substances come in contact with one another?(1 point)

Question

Responses

conduct a test to determine the chemical makeup of the molecules
conduct a test to determine the chemical makeup of the molecules

monitor for the release of a gas
monitor for the release of a gas

test for the release of heat
test for the release of heat

observe a color change

Answer 1

All the listed methods can be indicators of a chemical change, but each one individually may not be sufficient to confirm that a chemical change has occurred. Chemical changes involve the formation of one or more new substances with different properties from the reactants. Here's how each of the given options can be associated with a chemical change:

1. Conduct a test to determine the chemical makeup of the molecules: This is a reliable way to confirm a chemical change because it involves analyzing the substances before and after the reaction to verify that new chemical species have been formed.

2. Monitor for the release of a gas: The release of a gas can indicate a chemical reaction, such as when an acid reacts with a carbonate to produce carbon dioxide gas. However, physical changes can also involve gas release (like boiling), so this on its own isn't always proof of a chemical change.

3. Test for the release of heat: Exothermic reactions release heat, which can be a sign of a chemical change. However, physical changes may also involve temperature changes (e.g., the release of heat when water condenses), so additional evidence would be needed to confirm a chemical change.

4. Observe a color change: A change in color can suggest that a new substance with different properties has been created, which is indicative of a chemical change. However, there are physical changes that can also cause color changes (e.g., heating a metal can change its color without altering its composition).

The most direct and conclusive method among these options is to conduct tests to determine the chemical makeup of the molecules involved in the reaction, as this directly assesses whether new chemicals have been formed. The other methods can support the evidence of a chemical change but often require additional information or context to confirm a change in chemical composition.

Answer 2

what is the correct answer

Answer 3

The most correct answer among the options provided for observing that a chemical change has occurred is:

Conduct a test to determine the chemical makeup of the molecules.

This method directly analyzes the substances before and after the interaction to confirm whether a chemical change has taken place by identifying the formation of new substances with different molecular structures. The other methods (monitoring for the release of gas, testing for the release of heat, and observing a color change) can provide evidence of a chemical reaction, but they are not as definitive on their own as conducting a chemical analysis.