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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)

Responses

observe a color change
observe a color change

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

conduct a test to determine the chemical makeup of the molecule

3 answers

All of the options listed can indicate that a chemical change has occurred, but the most reliable observations typically include:

  1. Observe a color change - This can indicate a new substance has formed.
  2. Monitor for the release of a gas - Bubbles or gas escaping often suggest a chemical reaction.
  3. Test for the release of heat - An exothermic reaction releases heat, which is a sign of a chemical change.
  4. Conduct a test to determine the chemical makeup of the molecule - This is more formal and would typically be done to confirm a change after observing other signs.

Among these, observing a color change, monitoring for the release of a gas, and testing for the release of heat are considered direct indicators of a chemical change. If you have to pick one, "observe a color change" is often the most immediate and visible indicator. However, all are valid in different contexts.

Can you do a process of elimination to determine only 1

Sure! Let's go through the options with a process of elimination to determine the best single reliable way to observe a chemical change:

  1. Observe a color change: This can indicate a chemical change, such as the formation of a new substance. However, color changes can also occur in physical changes (e.g., mixing paints) or due to other factors like temperature.

  2. Monitor for the release of a gas: The formation of gas (bubbles) is a strong indicator of a chemical change, as it typically suggests that a reaction is taking place.

  3. Test for the release of heat: The release or absorption of heat can indicate a chemical change (exothermic or endothermic reactions), but it requires measurement tools and is not always observable without instrumentation.

  4. Conduct a test to determine the chemical makeup of the molecule: This is very definitive but requires specific testing and equipment. It's not something easily observed in the moment.

Final elimination:

  • Color change and heat release can be ambiguous and may not conclusively indicate a chemical change when observed alone.
  • Conducting a test for chemical makeup requires tools and isn't an immediate observation.

Thus, the most reliable single observation that a chemical change has occurred when two substances come into contact with one another is:

Monitor for the release of a gas.