Signs of chemical reactions include color change, energy change, the formation of a precipitate, production of gas bubbles, and change in temperature.
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One of the signs of a chemical reaction is the formation of a precipitate. When two liquids react and the product is a solid, it is called a precipitate. The precipitate forms because the solid (AgCl) is insoluble in water. That is true for all precipitates – the solids are insoluble in aqueous solutions. Precipitation reaction occur all around us.
Chemical reactions resulting in a precipitate happen all around us. A kidney stone is a precipitate. They are often made of calcium ions (from cheese) and oxalates. It is often suggested that a good way to avoid kidney stones is to drink a lot of water. This helps because the solubility of the precipitate increases with the amount of water. Drinking lots of water can help you avoid producing this particular precipitate.
Hard water is another example of a precipitate. Sometimes the pipes in our homes get clogged because precipitates of magnesium and calcium oxides have deposited themselves within the pipes.
Chemical Reaction One
We tried to produce several precipitates in the lab. For the first precipitate, we combined ammonia and Epson salt solution. We put a drop of food coloring in the Epson salt solution. We used a cotton string to slowly pull the ammonia over to mix with the Epson salt solution. This also gave the precipitate something to adhere to.
It took several hours to produce something visible. Here you can see the precipitate begin to form.
The Second Chemical Reaction
For this chemical reaction we combined a solution of sodium carbonate and a solution of magnesium sulfate. One solution was poured into the other which produced an immediate precipitate.
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Standards Addressed include NGSS MS PS1-2 and Utah SEEd 8.1.3
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