Mixtures+and+Solutions

__**POM-11 (Pure Substance or a Mixture?)**__ Our investigative question for this activity was **"How can you distinguish between a pure substance and a mixture?"**

The key ideas of this activity were: - that PURE substances act and appear the **same through the sample for all tests and observations** we make for them (because they are **made of only one substance**). - that MIXTURES will act and/or appear **different in at least one way for the tests and observations** (because they are **made of two or more substances**).

Because of the above definitions of pure substances and mixtures, no one test can prove a substance is pure (only support or suggest something is pure) but any test or observations showing a substance acts in at least two ways within the same sample must be a mixture.

__**POM-12 (Adding Water)**__ Our investigative question for this activity was **"What happens when substances are mixed with water?"**

What we found is that there are a few different things that can happen when a substance is mixed with water. - They can DISSOLVE (when a substance disappears into another substance when mixed). - This would mean that substances are SOLUBLE (the substances can be mixed together). - Sometimes these soluble mixtures form SOLUTION (when a substance dissolves completely to make a transparent liquid mixture). An AQUEOUS SOLUTION is such a mixture in water. - They could be INSOLUBLE (the substances do not mix together).

We will also define the substance being added as the SOLUTE and the substance (usually a liquid) the solute is being dissolved in as the SOLVENT.

Our investigative question was **"How much solute will dissolve in a solvent (do all solutes dissolve the same amount in a solvent)?"**
 * __POM-13 (Dissolving a Solute in a Solvent)__**

We discover in this investigation that soluble is NOT a yes or no question. Some substances will only dissolve a small amount while other substances might dissolve much more in the same solvent. The measure of how soluble a substance is is called SOLUBILITY.

__**POM-14 (Mass, Volume and Dissolving)**__ The investigative question for this activity was "**How does dissolving affect the mass and volume of a mixture?"**

The class found the when mixing the mass of the mixture remained constant (the sum of the masses of the solute and the solvent) while the volume decreased slightly (compared to the total volume of the solute and solvent). The **mass did not change** which supports the Law of Conservation of Mass (matter cannot be created or destroyed in a physical or chemical process). The **volume on the other hand decrease** because the molecules of the two substances fit together well enough to fill some of the spaces between the molecules. This allows the mixed solution be smaller in volume than to two separate parts.

We also discussed that we can dissolve more solute if we either increase the temperature of the solvent or increase the amount of the solvent we use. Both of these approaches increase the space between molecules that solute can fit inside of.