Solutions: Crash Course Chemistry #27

CrashCourse
19 Aug 201308:20
EducationalLearning
32 Likes 10 Comments

TLDRThe video examines solutions from several perspectives, explaining key properties like molarity, molality, and mass percent. It explores how molecular structure and polarity allow different substances to dissolve, using vivid examples like pufferfish toxin and carbonated sodas. Other factors affecting solubility are also covered, including pressure as described in Henry's Law and temperature, which impacts oxygen levels in water critical for cold-water fish. The summary provides a compelling overview of the key concepts to pique viewer interest.

Takeaways
  • 😀 A solution is a mixture where particles of a solute are dissolved in particles of a solvent
  • 😶‍🌫️ The solubility of a solution depends on molecular structure, pressure, and temperature
  • 😵‍💫 Molarity, molality, and mass percent are ways to quantitatively describe a solution
  • 🥴 Polar solutes tend to dissolve in polar solvents, and vice versa for nonpolar substances
  • 😮 Henry's Law relates gas solubility to its partial pressure above the solution
  • 😲 Increasing temperature decreases gas solubility but increases solid solubility in liquids
  • 🤪 The partial pressure of CO2 is much higher inside a sealed soda can to keep it dissolved
  • 😵 Tetrodotoxin in pufferfish can dissolve in and disrupt nerve cell membranes due to polarity
  • 😨 Cold water holds more dissolved O2 which fish need to breathe
  • 🤓 The concentration, pressure and temperature of solutes and solvents determine solubility
Q & A

  • What three factors affect the solubility of a solution?

    -The three main factors that affect solubility are: molecular structure (polarity), pressure, and temperature.

  • How can you precisely describe the concentration of a solution?

    -There are a few ways to precisely describe the concentration of a solution, including: molarity (moles of solute per liter of solution), molality (moles of solute per kilogram of solvent), and mass percent (mass of solute divided by mass of solution, multiplied by 100).

  • Why is tetrodotoxin dangerous to humans?

    -Tetrodotoxin is very polar, so it dissolves easily in the aqueous solutions within the human body. It then binds to sodium channels and interferes with the nervous system, potentially causing paralysis, suffocation, and death.

  • How does pressure allow carbon dioxide to dissolve in soda?

    -According to Henry's Law, for a gas to dissolve in a liquid, the partial pressure of that gas above the solution must equal or exceed the pressure exerted by the gas trying to escape the solution. The high pressure allows more CO2 to dissolve.

  • Why does hot water dissolve less oxygen than cold water?

    -Gas solubility decreases as temperature increases because warmer gas molecules have more kinetic energy and are more likely to escape the liquid surface. So cold water can dissolve more oxygen gas.

  • What happens when you open a can of cold soda?

    -When you open the can, the pressure drops to atmospheric levels. This lower pressure allows a rush of carbon dioxide bubbles to escape from the soda.

  • How does polarity affect solubility?

    -Polar solvents dissolve polar solutes well, while nonpolar solvents dissolve nonpolar solutes. This is because the molecular interactions have to be favorable for dissolution to occur.

  • Why is puffer fish dangerous for humans to eat?

    -Puffer fish contains tetrodotoxin poison, which is very dangerous to humans. If the chef does not carefully remove the poisonous parts, it can cause paralysis, suffocation, and death.

  • How does temperature affect gas vs solid solubility differently?

    -As temperature increases, the solubility of solid solutes generally increases, while the solubility of gas solutes decreases. This is because gases have more kinetic energy to escape liquids at higher temperatures.

  • Why are cold water fish like trout sensitive to summer heat waves?

    -Cold water can dissolve more oxygen than warm water. So when summer heat reduces oxygen levels in the water, it can be harmful to cold water fish like trout that rely on high oxygen availability.

Outlines
00:00
😀 The Science of Breathable Air

This paragraph discusses the complex variables that allow us to breathe air. It explains that air is a solution, containing oxygen dissolved in nitrogen and other gases. For a gas to dissolve in a solution, properties like molecular structure, pressure, and temperature need to be just right.

05:00
😊 How Concentration of Solutions is Measured

This paragraph introduces different ways to quantify the concentration of a solution, including molarity, molality, and mass percent. It provides an example calculation of the mass percent of sugar in soda. It then explores why some substances like sugar dissolve easily in water, while others like oils do not - this depends on the molecular polarity and how the molecules interact.

Mindmap
Keywords
💡solution
A solution is a mixture of a solute dissolved in a solvent. The video discusses different types of solutions, like the air we breathe, which is a mixture of gases like oxygen and nitrogen. It also talks about the solution inside a can of soda, which contains dissolved carbon dioxide gas. Solutions are important in the video because their properties depend on factors like molecular structure, pressure and temperature.
💡polarity
Polarity refers to the separation of electric charge in a molecule, leading to a positively charged end and a negatively charged end. The video explains that similarity in polarity allows solutes and solvents to mix, like sugar dissolving in water. It also enables toxins like tetrodotoxin to dissolve in the human body.
💡pressure
Pressure, specifically partial pressure in the case of gases, affects how much of a gas can be dissolved in a liquid solvent. The video discusses how carbon dioxide is forced to dissolve in soda at high pressures. When the pressure is released, the gas forms bubbles.
💡temperature
Temperature impacts solubility in different ways for solid and gaseous solutes. For solids dissolved in liquid solvents, solubility increases with higher temperatures. But for gases, solubility decreases at higher temperatures due to higher kinetic energy and pressures.
💡toxicity
Toxicity is an important concept as the video analyzes the lethal effects of incorrectly prepared fugu fish. The toxin tetrodotoxin can kill via paralysis and suffocation due to its polarity enabling it to interfere with the human nervous system.
💡oxygen
The video emphasizes how the specific concentration of oxygen in air is vital for human respiration. It gives the example of oxygen levels in water dropping due to heat waves, preventing cold water fish from getting enough oxygen.
💡carbon dioxide
Carbon dioxide gas dissolved in liquids is essential for carbonated sodas. The script analysis the concentration of CO2 and the volumes of gas released when opening a can.
💡Henry's law
Henry's law allows calculation of the concentration of a dissolved gas based on its partial pressure and constants representing its solubility. The video uses it to determine the concentration of CO2 gas dissolved in a can of soda.
💡molarity
Molarity measures the number of moles of solute present per litre of solution. It is one way the video suggests precisely specifying the concentration of a solution.
💡mass percent
Mass percent measures the mass of solute as a percentage of the total mass of the solution. It is another method for quantitatively describing solution concentration that the video outlines.
Highlights

The air we breathe is a solution - a mixture where oxygen and other gases are dissolved in nitrogen.

Solutions can be described by molarity, molality or mass percent to quantify the amount of solute dissolved.

Polarity determines if a solute will dissolve in a solvent - similar polarities allow favorable interactions.

Tetrodotoxin's polarity allows it to dissolve in the water in our bodies and bind to sodium channels, disrupting nerves.

Henry's Law: The concentration of a dissolved gas equals its partial pressure over the solution times a solubility constant.

Increasing pressure of CO2 outside a solution increases the amount that can be dissolved by countering molecules escaping.

Solubility of gases decreases as temperature rises, while solubility of solids in liquids generally increases with temperature.

Cold water can dissolve more oxygen for fish to breathe compared to warm water.

Fugu fish is adapted to warmer waters so heat waves don't impact its oxygen levels as much as cold water fish.

Solutions are described by concentration measures like molarity, molality and mass percent.

Polarity similarity between solute and solvent allows dissolution.

Henry's law relates dissolved gas concentration to its partial pressure and solubility constant.

There's a lot of dissolved CO2 contributing to soda's carbonation and burping.

Increasing temperature typically increases solid solubility but decreases gas solubility.

Colder water holds more oxygen, needed by fish to breathe, compared to warmer water.

Transcripts

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