SOLUCIONES. SOLUBILIDAD, CLASES DE SOLUCIONES, CONCENTRACION DE UNA SOLUIÓN

Main ideas and lessons (Solutions, Solubility, Concentration)

1) What a solution is

• A solution is a homogeneous mixture (its components are mixed evenly).
• Mixtures come in two types:
  • Homogeneous mixtures: components are blended so that only one phase is visibly present.
  • Heterogeneous mixtures: components do not blend and remain separate (often multiple visible phases).
• A solution is made from:
  • Solute: the substance that is dissolved (typically in smaller proportion).
  • Solvent: the substance that dissolves the solute (typically present in larger proportion).
• A solution can have multiple solutes, but there is always one solvent.

2) Examples and types of solutions (by physical state)

• Liquid solutions: e.g., water + alcohol.
• Liquid + solid: e.g., water + salt.
• Liquid + gas: e.g., soda contains dissolved carbon dioxide (CO₂).
• Gaseous solutions: e.g., air (mixture of nitrogen, oxygen, CO₂, and pollutants).
• Solid solutions: e.g., steel (alloy of iron and carbon).
• Other everyday examples:
  • Coffee with milk: water (solvent) dissolves coffee components, sugar, and milk components.
  • Salt water: salt = solute, water = solvent.
• Contrast case:
  • Oil + water do not form a solution because oil does not mix with water.

3) Why some substances dissolve and others don’t (“Like dissolves like”)

• Key idea: “Like dissolves like”
  • Polar substances (with partially positive and partially negative ends) dissolve well with other polar substances.
  • Nonpolar substances dissolve with other nonpolar substances.
• Salt and water
  • Water is polar and salt is ionic (has positive and negative charges).
  • Salt ions interact with opposite charges in water, allowing dissolution molecule by molecule.
  • Opposite charges attract → salt dissolves well in water.
• Oil and water
  • Oil is nonpolar (no charge separation like water).
  • When placed together, oil molecules tend to stay with each other and separate from water.
  • Polar substances do not dissolve in nonpolar substances (and vice versa).
  • To dissolve oil, a similar nonpolar dissolving medium is suggested (e.g., ether or benzene).

---

4) Solubility

Definition

• Solubility = the maximum amount of a substance that can dissolve in a given amount of solvent (the example uses 100 g of water) at a stated temperature.

Example calculation (sodium chloride in water at 25°C)

• Start with 100 g of water at 25°C.
• Add sodium chloride gradually:
  • It dissolves well up to about 36 g.
• If you add 37 g total (i.e., the 37th gram):
  • The extra amount does not dissolve and instead precipitates (sinks to the bottom).
• Conclusion from the example:
  • Solubility of NaCl ≈ 36 g per 100 g of water (at the stated temperature).

Classification of solutions based on solute amount

1. Unsaturated solution
   • Contains less than the solubility limit.
   • More solute can still dissolve.
   • Example: if solubility is 36 g, adding 20 g is unsaturated.
2. Saturated solution
   • Contains exactly the maximum solute that can dissolve.
   • No extra solute will dissolve.
   • Example: add 36 g NaCl → saturated.
3. Supersaturated solution
   • Contains more than the solubility limit.
   • Excess solute does not stay dissolved; it precipitates.
   • Example: if the limit is 36 g and you add 40 g:
     • 4 g will not dissolve and will precipitate,
     • while 36 g remains dissolved.

---

5) Factors that affect solubility

A) Nature of solute and solvent

• Solubility depends on whether solute and solvent are similar:
  • Similar (polar-with-polar, nonpolar-with-nonpolar) → dissolves better.
  • Dissimilar → dissolves poorly.

B) Temperature

• Temperature affects solubility for most solutes.
• General trend: in many cases, higher temperature increases solubility.
• Three behaviors described (using a graph concept):
  • Solute A: solubility increases as temperature rises (e.g., sugar in hot vs. cold water).
  • Solute B: solubility stays constant (not affected by temperature in the example).
  • Solute C: solubility decreases as temperature rises (analogy: some ingredients dissolve in cold water but clump in hot water).
• Conclusion: temperature can increase, decrease, or not change solubility depending on the solute.

C) Pressure (important mostly for gases)

• Increasing pressure increases the solubility of gases in liquids.
• Example:
  • In soda, CO₂ dissolves due to pressure.
  • When the cap is opened and pressure is released, the gas escapes.

---

6) Concentration of a solution

Definition

• Concentration measures the amount of solute present in a given amount of solvent.

Why it’s important

• Helps determine exactly “how much” solute is present.
• Important in:
  • laboratory work
  • chemical laboratories
  • clinical laboratories

Ways concentration can be expressed (units/formulas mentioned)

The lesson indicates later calculations will cover concentration units such as:

• percentage by mass (mass percentage)
• volume to volume percentage (v/v)
• mass volume
• molarity-like / related modality (appears as “modality/modality”)
• parts per million (ppm)
• terms listed under subtitles such as polarity / similar items

Practical meaning of percentage labels (examples)

• If a milk label says 10% protein:
  • For every 100 parts (e.g., 100 g) of milk, 10 parts are protein.
• If it also says 5% fat:
  • For every 100 g, 5 g is fat (and 10 g is protein as stated).
• Scaling with volume consumed:
  • If you drink 200 mL instead of 100 mL, the quantities double (e.g., protein becomes ~20 g for the same basis).

How to change concentration

• To increase concentration:
  • Add more solute (e.g., add more salt to salt water).
  • Evaporate the solvent (remove water → solute becomes more concentrated).
• To decrease concentration:
  • Dilute the solution by adding more solvent.

---

Speakers / sources featured

• No specific named speaker or external source is identified in the subtitles.
• The content appears to be delivered by an unnamed instructor/teacher addressing “Welcome, student!”.