Hey there!
Chemical changes are changes in object's chemical compounds and chemical compositions, and often can't be reversed.
Here's an example:
If you have a piece of paper and you happen to burn it, that can't be reversed.
In other words, it can't be "un-burned". Nothing can restore it to its previous state.
Hopefully this helped!
Answer:
298.9 million years ago - 251.902 million years ago
Explanation:
It might be in the 2011 Earth Science Review Packet so maybe go check that out
To balance Ca + Cl2 = CaCl2 you'll need to be sure to count all of atoms on each side of the chemical equation.
Once you know how many of each type of atom you can only change the coefficients (the numbers in front of atoms or compounds) to balance the equation for Calcium + Chlorine gas.
The answer is Argon! From Ne you go 2 3s level elements and then 6 3p level elements
They are kind of opposite processes. Chemical synthesis is execution of chemical reactions to make products. Like you take two substances, you put them together, they react and you have new a substance. For example.

here Sodium and Chlorine react to make a new substance which is Sodium Chloride.
Chemical decomposition is process of seperating a substance to different substances. There is a substance by a reaction this substance becomes two substances, Like : XY -> X+Y For example :