Understanding Solutions Chapter 7 Section1

Solutions A solution is a homogenous mixture where the components of the mixture are evenly mixed. Looks uniform: color, density, texture. . . In a solution, one substance is dissolved into another substance: Solute: the substance that is dissolved (smaller amount) Solvent: the substance that is doing the dissolving (larger amount) Salt Water Carbonated Water

Dissolving The movement of molecules causes the solute to break apart and mix evenly throughout the solvent. – physical change Liquids and gases dissolve easily. Solid alloy solutions must be melted for dissolving to occur. A liquid dissolves a solid at the surface of a solid. Since water is a polar molecule, it works well as a solvent. This is why it’s called:

Can we reverse dissolving? Supposed you dissolve a teaspoon of salt into a glass of water. Is it possible to recover the salt from the water?

Common Solutions Look at each of these common solutions. What is the solute? What is the solvent? How is each one of these solutions formed?

Colloids A colloid is a mixture that contains small, un-dissolved particles that do not settle out. Small enough to not be seen Large enough to “scatter light” or give a creamy or opaque texture Examples: Milk, Gelatin, Mayo, Shaving Cream, Whipped Cream. . .

Is Fog/Mist a Solution or Colloid? What are the two things being mixed? Are they chemically combined? Or just mixed?

Suspensions A suspension is a mixture in which particles can be seen and easily separated by settling or filtration. No uniform properties Visible particles Examples: Heterogeneous Mixture, Snow Globe, Mud, Oil & Water

Compare & Contrast Type of Mixture Does it Settle Out? Particle Size Does it scatter Light?

Ionic and Molecular Compounds Salt Water – Ionic Compound mixes with Water Positive and Negative Ions are attracted to the polar water molecules Conducts electricity Salt Water Dissolving Link on Moodle! Sugar Water – Molecular Compound mixes with Water Polar water molecules attract the sugar molecules and force them apart in the solution, spreading the solute throughout the solvent. Doesn’t conduct electricity

Effects of Solutes on Solvents Lower Freezing Points Example: Salt Water (again!) Pure Water Freezes at _______ ˚F / ________˚C Salt freezes at a higher/lower temperature So which freezes first: ocean or lake? Higher Boiling Points Example: Coolant Pure Water Boils at _______ ˚F / ________˚C Antifreeze boils at a higher/lower temperature So which is safer for your car: water or coolant?

Check your knowledge! Identify each Mixture: Correctly match the vocabulary words below:

The Chemistry of Ice Cream