mixing cement with water is a irreversible change
Portland cement (and the concrete, mortar, thin set, or other masonry product made from it) doesn't dry. Rather, it cures by a chemical reaction initiated by putting water in it. The reaction is irreversible; hence, adding water to cement is an irreversible change.
Mixing cement and water is a reversible change because the two substances can be separated by allowing the water to evaporate, leaving the solid cement behind. This process does not alter the chemical composition of either the cement or the water.
Mixing Alka-Seltzer and water is a reversible change because it can be undone by allowing the water to evaporate, leaving behind the original substances in their initial forms.
The water should be added last. All the aggregate materials and the cement should be thoroughly mixed before the water is added.
reversible
Portland cement (and the concrete, mortar, thin set, or other masonry product made from it) doesn't dry. Rather, it cures by a chemical reaction initiated by putting water in it. The reaction is irreversible; hence, adding water to cement is an irreversible change.
Mixing cement and water is a reversible change because the two substances can be separated by allowing the water to evaporate, leaving the solid cement behind. This process does not alter the chemical composition of either the cement or the water.
It is reversible. You can allow the water to evaporate, leaving the salt behind.
Sugar and Salt
Mixing Alka-Seltzer and water is a reversible change because it can be undone by allowing the water to evaporate, leaving behind the original substances in their initial forms.
no
Irreversible
A. Cement
cement
The water should be added last. All the aggregate materials and the cement should be thoroughly mixed before the water is added.
the strength of concrete is effected by water /cement ratio as the water/cement ratio increases the strength of the concrete decreases
That depends on what is being mixed together. Two examples of this are: If you mix sand, gravel, and water it is reversible and you can separate the mixture back to its original three parts. If you mix sand, gravel, water, and cement powder it is not reversible as the water will react with the cement powder creating liquid cement and the sand and gravel will form concrete with the liquid cement. After a few hours the liquid cement in the concrete will set and the concrete mixture will become as hard as rock. It is now no longer possible to separate the mixture back to its original four parts.