When using a liquid as a solvent, what could be the state(s) of matter of the solute? when trying to dissolve a liquid, what could be the state(s) of matter of the solvent? when using a gas as a solvent, what could be the state(s) of matter of the solute? when trying to dissolve a solid, what could be the state(s) of matter of the solvent?

When using a liquid as a solvent, the state(s) of matter of the solute are likely to be:

Gas Solid Liquid  

When trying to dissolve a liquid, the state(s) of matter of the solvent would likely be:

LiquidSolid

When using a gas as a solvent, the state(s) of matter of the solute is likely:

Gas  

When trying to dissolve a solid, the state(s) of matter of the solvent would likely be:

SolidLiquid

According to the given question, we are meant to show the different forms of matter which a solid, liquid or gaseous phase can be changed to on different circumstances.

As a result of this, we can see that liquid as a solvent would act as a good agent in different kinds of matter as even oxygen dissolve in water which enables sea animals breathe.

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1. When using a liquid as a solvent, what could be the state(s) of matter of the solute?
gas, solid, liquid
Liquid as solvent could dissolve all kind of matter. Oxygen(gas) dissolve in water and it is the reason why fish could "breath" under water. Sugar and many other solid substances are easy to dissolve in water. Alcohol(liquid) also could be dissolved in water.

2. when trying to dissolve a liquid, what could be the state(s) of matter of the solvent?
liquid, solid
Dissolve a liquid means that the liquid becomes the solute. From the answer of first question, you should infer that liquid solvent would be able to dissolve in liquid. The example of liquid dissolved in solid would be mercury and gold, which will create an amalgam.

3. when using a gas as a solvent, what could be the state(s) of matter of the solute?
gas
Gas only be able to dissolve another gas. The density difference of gas and other matter normally too far which makes them hard to catch a liquid/solid material.

4. when trying to dissolve a solid, what could be the state(s) of matter of the solvent?
solid and liquid
Dissolve a liquid means that the solid becomes the solute. The example of solid that dissolved in solid would be bronze or alloy which is a mixture of two or more metals. Solid in a liquid example can be found in first question answer, it's like adding sugar to water.