 All right the last thing you need to know are the common indicators of chemical change You have to Understand that any of these things that are happening spontaneously tell you that a chemical reaction is occurring There can be a spontaneous change in color and again. It's spontaneous. It's not that I'm talking about taking a can of red paint and Painting a wall. That's not a chemical reaction. That's not a chemical change. I'm putting the new paint on the wall I'm changing its color. I'm talking about things that change color on their own like the leaves changing in the fall When the leaves change in the fall that indicates that there's a chemical reaction taking place the chlorophyll is actually breaking down and That green color is disappearing because of the decomposition of the chlorophyll It's got to be spontaneous Bubbling is another common indicator of chemical change and again I'm not talking about taking a straw putting it in the glass of water and blowing you're making the bubbles There's nothing spontaneous about that. It's more like mixing vinegar and baking soda You mix the two things together in a bubbles on its own. It does it spontaneously The bubbles you're seeing are a new substance. It's carbon dioxide gas. You didn't start with carbon dioxide You made carbon dioxide. That's why it bubbles It's a change in state that's occurring because of the formation of the new substance The formation of precipitate you mix two liquid things together and you get a solid and again, we're talking spontaneous here We're not saying I put it in the freezer and I made a solid I just mixed two aqueous things together and it became solid. It did it all on its own What you're seeing there is a state of a new substance that new substance is called a precipitate chemical reaction and Again change not on but in odor So it happens when you type these things quick to try to get them ready in time change in odor All of a sudden it starts smelling like bananas Not that you cut up a banana, but that it smells like bananas when you mix two things together That means you made a compound that has the smell of bananas. You made something new Again, it's got to be spontaneous. You didn't spray banana scented air freshener You just mix two things together that did not smell like bananas and all of a sudden it smells like bananas This is a odd one and oftentimes. I don't even mention it because you sure you really shouldn't be smelling chemicals a lot of them have very harmful fumes that can burn the inside of your nose and stuff like that, so I Generally tell students not to smell things, but there are some instances I remember an organic chemistry lab when I was in college. We made the banana ester So one of the ways to know that your experiment went correctly was to smell it and make sure it smelled like bananas Last one is change in temperature. Every chemical reaction involves some kind of change in energy Either an increase or decrease in energy That correlates to either an increase or decrease in temperature Whenever a reaction produces a lot of excess energy it causes the temperature to go up. We call that exothermic and Whenever a reaction soaks up energy like a sponge We see a decrease in temperature. We call that endothermic These spontaneous changes in temperature and again, I'm not talking about putting in a microwave If you put something in a microwave and push start, you're just heating it up You're just making the water molecules vibrate faster. There's nothing chemical about that But if I mix together two things that are room temperature and all of a sudden it gets really hot It's producing that heat all on its own. It's producing it spontaneously That would be a chemical change best example and the one that I mentioned in the little thing I typed up is those hot hands hand warmers It's that time of year where people start buying those things to keep in their pockets of football games or when they go hunting When you take those things out of the packet it starts reacting with the oxygen in the air and all on its own It begins to get hot. That's an exothermic reaction. That's a spontaneous increase in temperature That's an indicator that a chemical change has taken place