Basics of Atoms & Bonding and Chemical Reactions

How to Identify Chemical Reactions

There are five ways to identify a chemical reaction has taken place: When it has changed color, when a precipitate has been formed (solid), Gas formation (bubbles), change in property (like texture) and Change in Energy:

A solid may appear when two solutions are mixed, solids which are formed in chemical reactions are called precipitates.

A gas may be produce, both in a solid and in a liquid. If it occurs in a liquid you may see the gas as bubbles.

The texture might also indicate that a chemical change has occurred. This does not mean that every time you see a physical change means that a chemical reaction has been taken place.

Finally there might be changes in energy. Exothermic reaction and endothermic reaction. The exothermic reaction means that it released energy, and the endothermic reaction means that it has absorbed energy.

In the picture above a precipitate has formed.

In this video what happens is that First Bill(the guy) has a piece of iron wool, and runs electrons through it. A chemical reaction occurs. You know this because you see color change and property change. Then he places the same iron wool but in a closed system with a lot of oxygen and a huge explosion takes place. This happens because the electrons are recombining with other electrons. Energy is released through exothermic reaction. In the other reaction he separated hydrogen from oxygen and recombined them through popping a balloon, expecting little water vapor to appear somewhere in the room.

In this video on the right, what happens is that they place Mentos candy in Diet Coke and wait for it to explode. This happens because the Mentos have tiny little pores in which carbon dioxide is released when it has contact with the coke, causing it to explode. You can notice there has been a chemical reaction because of bubble formation.

In this video what happens is that they place a Bromine tablet in rubbing alcohol and waited. After a few seconds a chemical reaction started taking place. You can notice this because you can see color change, and bubble formation. After the chemical reaction, the tablet had completely dissolved.