Mixing Materials
Home Up Mixing Materials Mixing Molecular Materials Mixing Ionic Materials with Water Solubility Rules

 

Mixing Materials

What happens at the molecular level when materials mix together to form solutions? The ability of molecular materials to mix with one another depends, to a very great extent, on intermolecular bond types.

We will go into specifics soon, but first let's look at the basic idea of mixing as shown here. This "equation", if I can call it that, starts on the left with two materials, A and B, which have not yet been mixed. The right side of this "equation" shows the two materials after they have been mixed. What has happened to them in the process? The bonds holding the A's together were broken. The bonds holding the B's together were also broken. New bonds holding A and B together have been formed.
A A A A
A A A A
A A A A
A A A A

+
B B B
B B B
B B B

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A B A A A
B A A B A
A B B A A
A B A B A
A A B A B

In some ways this is like elements combining to form a compound, however it is not necessary for there to be a fixed ratio here. Also, we are not necessarily talking about covalent, ionic and metallic bonds, which we would be talking about if we were talking about making a new compound. In this case, there can be any number of A's mixed in with the B's. An example of this is shown in part B. The same thing is happening, it's just that the proportions are different. This process can be exothermic or endothermic depending on the strength of the bonds involved and whether more or less energy is released in making A-B bonds than is used in breaking A-A and B-B bonds.

In general, for mixing to occur, the bond strengths of A-A, B-B and A-B have to be comparable to one another. Otherwise, the materials will not mix very well. If, for example, the A-A bonds were much stronger than the B-B bonds, the A's would not separate from one another to let the B's in and no mixing would occur.

Next, we will apply these ideas first to the process of mixing molecular materials and then to mixing ionic materials with water.

 

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