Which of the following is a sign a chemical reaction has occurred?

A blue liquid is mixed into a yellow liquid, and the mixture turns green.
A piece of metal is placed in water and produces sparks and gas.
A liquid is heated on a hotplate, and bubbles form.
A solid powder is mixed into a liquid and disappears.

Question

Which of the following is a sign a chemical reaction has occurred?

A blue liquid is mixed into a yellow liquid, and the mixture turns green.
 A piece of metal is placed in water and produces sparks and gas.
 A liquid is heated on a hotplate, and bubbles form.
 A solid powder is mixed into a liquid and disappears.

Extrinix · Answer

What is your understanding of a Chemical Reation?

Extrinix · Answer

Reaction*, apologies.

kekeman · Answer

In chemical changes atoms are rearranged into new substances

kekeman · Answer

-Change in temperature
-Change in color
-Bubbles
-Precipate Forming
-When light is giving
-Change in smell (odor)
-Taste
-When the changes are difficult to reverse
-Boiling is not a chemical reaction even though there are bubbles

kekeman · Answer

All signs

kekeman · Answer

I say it's either B or C but idk

Extrinix · Answer

Well think closer, it's a chemical reaction, meaning that it has to contain two substances to start a reaction.

xWFLif3x · Answer

All of them do. The last one could be dissolution, though.

kekeman · Answer

Well look what the questions asking it is asking which of the following is a SIGN

kekeman · Answer

And i can only pick one answer

Vocaloid · Answer

Process of elimination:

A blue liquid is mixed into a yellow liquid, and the mixture turns green. ---> a color change is a possible sign of a chemical reaction. However, there's a good chance the color change is simply due to the combination of blue and yellow.

A liquid is heated on a hotplate, and bubbles form. ---> like your notes say, boiling is not a chemical reaction

A solid powder is mixed into a liquid and disappears. ---> this is most likely because the solid dissolved. this is most likely not a chemical reaction.

A piece of metal is placed in water and produces sparks and gas. ---> this is the most likely chemical change. no heating is mentioned, so the gas is most likely a new product rather than a gaseous form of the original reagent. additionally, sparks are a sign that heat is being produced from the metal-water interaction, which is another sign of a chemical reaction.

kekeman · Answer

Yes i agree thanks for the help :)