When two substances come into contact and a chemical change occurs, there are several reliable indicators you might observe. Here are some common signs that a chemical change has taken place:
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Color Change: A noticeable change in color, not just the mixing of colors, can indicate that a new substance has formed.
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Gas Production: The formation of gas bubbles or smoke can suggest a chemical reaction. This may also be observed as effervescence.
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Temperature Change: An unexpected increase (exothermic reaction) or decrease (endothermic reaction) in temperature can indicate that a chemical reaction has taken place, even if no heat is applied externally.
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Precipitate Formation: The formation of a solid from a solution, which settles at the bottom or forms a cloudy mixture, suggests a chemical reaction.
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Odor Change: The production of a new odor, or a change in the smell of the substances involved, can indicate a chemical change.
Any one or a combination of these signs can serve as reliable evidence that a chemical change has occurred when two substances are mixed.