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Signs of a Chemical Reaction-Precipitate

Signs of chemical reactions include color change, energy change, the formation of a precipitate, production of gas bubbles, and change in temperature.

Forming a precipitate

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.

chemical reaction forms a precipitate

It took several hours to produce something visible. Here you can see the precipitate begin to form.

forming a precipitate
Chemical Reaction forming a precipitate
Above you can see that the string is dry and stiff. A precipitate has formed. This is a sign that a chemical reaction has happened.

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.

Chemical Reaction to Produce a Precipitate
The Formation of a Precipitate and Also a Color Change

Are you teaching chemical reactions for middle school? I have a resource that explores these chemical reactions.

draining the precipitate
We drained the precipitate with a coffee filter.
After the precipitate is dry you can see that it is a solid form.
The Dried Precipitate

Would you like a free sample from this unit? Get your free resource here.

This resource aligns with the following standards:

Standards Addressed include NGSS MS PS1-2 and Utah SEEd 8.1.3

Steel Wool Combustion
properties of substances before and after chemical reactions

Also available here on this site Teaching Science

scientific investigations
NGSS MS-PS1-2 and Utah SEEd 8.1.3
Complete Unit for NGSS MS PS1-2 and Utah SEEd 8.1.3

Thank you, and I hope you enjoy using this unit in your classroom!

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Forming a precipitate

Thank you, and I hope you enjoy using this unit in your classroom!

FREE Chemical Reaction Resource

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As always, Lynda provides perfect alignment with the standards.

 
Age of the Earth and Geologic Time Scale NGSS MS ESS1-4

Sharon M

Teaching Science with Lynda R. Williams
5
2016-05-03T18:24:44-06:00

Sharon M

As always, Lynda provides perfect alignment with the standards.   Age of the Earth and Geologic Time Scale NGSS MS ESS1-4
Thank you so much for creating this resource! It is such a fun and engaging activity for my students, especially during distance learning.

 
Honey Bee Digital Escape Distance Learning

Expedition Fourth

Teaching Science with Lynda R. Williams
2020-11-03T20:44:55-07:00

Expedition Fourth

Thank you so much for creating this resource! It is such a fun and engaging activity for my students, especially during distance learning.   Honey Bee Digital Escape Distance Learning
My students loved this unit. I was able to present different elements of it throughout the month. It is hard to find interesting non-fictional, age-appropriate text for my students that they will enjoy. This was a great unit that aligned well for my students who have very different goals within the same group.

 
Compare and Contrast Two Texts on Reindeer

Heidi J

Teaching Science with Lynda R. Williams
2020-11-03T20:45:49-07:00

Heidi J

My students loved this unit. I was able to present different elements of it throughout the month. It is hard to find interesting non-fictional, age-appropriate text for my students that they will enjoy. This was a great unit that aligned well for my students who have very different goals within the same group.   Compare and Contrast Two Texts on Reindeer
I am so impressed with this unit which manages to be distance learning and hands-on at the same time.  Really well thought out and engaging activities that allow students to practice each of the eight Science and Engineering Practices.  Really no prep for me!

 
Science and Engineering Practices Distance Education Unit

Tina S

Teaching Science with Lynda R. Williams
5
2016-05-03T18:05:39-06:00

Tina S

I am so impressed with this unit which manages to be distance learning and hands-on at the same time.  Really well thought out and engaging activities that allow students to practice each of the eight Science and Engineering Practices.  Really no prep for me!   Science and Engineering Practices Distance Education Unit
The elephant article was excellent but I also thought the lab on dissecting a flower was broken down so easily, even telling me where to get inexpensive flowers!  This resource helped me teach this challenging standard in an engaging way.  Worth every penny!

 
Structure and Function NGSS 4-LS1-1 and 4-LS1-2

Richard S

Teaching Science with Lynda R. Williams
5
2016-05-03T18:07:52-06:00

Richard S

The elephant article was excellent but I also thought the lab on dissecting a flower was broken down so easily, even telling me where to get inexpensive flowers!  This resource helped me teach this challenging standard in an engaging way.  Worth every penny!   Structure and Function NGSS 4-LS1-1 and 4-LS1-2
5
3
Teaching Science with Lynda R. Williams