Study sheet: Fluid Properties and Cardiac Flow

📋 Course Outline

1. Freezing Point Depression
2. Boiling Point Elevation
3. Osmosis and Osmotic Pressure
4. Tonicity and Oncotic Pressure
5. States and Structure of Water
6. Fluid Motion Principles
7. Heart and Blood Circulation
8. Cardiac Function and Turbulence

📖 1. Freezing Point Depression

🔑 Key Concepts & Definitions

• Freezing point depression : the lowering of a solvent’s freezing point when a solute is added

📝 Essential Points

• When salt is added to water, Na+ and Cl− ions attract water molecules and interfere with the formation of the large solid ice network, so the solution must be cooled to a lower temperature to freeze.

📐 Formula — The freezing point depression is calculated as $\Delta T_f=i\times K_f\times m$, where $\Delta T_f$ is the freezing point depression, $K_f$ is the solvent-dependent freezing point depression constant, $i$ is the van’t Hoff factor, and $m$ is molality.

💡 Memory Hook

Solute particles disrupt crystal formation → the solvent freezes at a lower temperature

📖 2. Boiling Point Elevation

🔑 Key Concepts & Definitions

• Boiling-point elevation : the increase in a solvent’s boiling point when a non-volatile solute is added

📝 Essential Points

📐 Formula — The boiling-point elevation is calculated as $\Delta T_b=T_b(\mathrm{solution})-T_b(\mathrm{solvent})=K_b\times m$, where $K_b$ is the boiling point elevation constant and $m$ is the solute molality in mol/kg solvent.

💡 Memory Hook

Pure solvent boils lower, whereas a solution with non-volatile solute boils higher

📖 3. Osmosis and Osmotic Pressure

🔑 Key Concepts & Definitions

• Osmosis : the passage of solvent through a semipermeable membrane from a low-solute-concentration solution or pure solvent toward a high-solute-concentration solution
• Osmotic pressure : the pressure that must be applied to the high-concentration side to stop osmosis

📝 Essential Points

• Osmotic pressure depends on solute concentration rather than solute identity, although an electrolyte contributes more particles per formula unit than a nonelectrolyte.

• Soaking meat in a concentrated salt solution dehydrates its cells, and osmosis causes surface bacteria to shrivel and die, extending the meat’s preservation without refrigeration.

💡 Memory Hook

Low solute concentration → membrane passage → high solute concentration

📖 4. Tonicity and Oncotic Pressure

🔑 Key Concepts & Definitions

• Tonicity : how an extracellular solution changes cell volume by affecting osmosis
• Oncotic pressure : the pulling force generated by plasma proteins that draws water into the blood compartment from surrounding interstitial fluid

📝 Essential Points

• The three tonicities are:
  • Hypotonic: lower extracellular osmolarity and cell expansion
  • Hypertonic: higher extracellular osmolarity and cell shrinkage
  • Isotonic: equal osmolarity and no net water movement

💡 Memory Hook

Hypotonic expands cells, hypertonic shrinks them, isotonic causes no net water movement

📖 5. States and Structure of Water

★ Must-know

• When water freezes, its molecules slow down, form more hydrogen bonds, and arrange into an open crystalline hexagonal structure, making solid water less densely packed than liquid water.

• As water boils, hydrogen bonds break and steam particles move far apart and rapidly, while above 100°C oxygen atoms are separated in steam rather than loosely linked in chains.

Further detail

• Liquid water molecules move freely and slide past one another while each molecule links to four others in a tetrahedral arrangement with fewer hydrogen bonds than in ice.

• Steam causes more severe burns than boiling water because steam releases the energy absorbed during hydrogen-bond breaking when it condenses into liquid water on the skin.

💡 Memory Hook

Solid: bonds organize; liquid: molecules slide; gas: bonds break and particles separate

📖 6. Fluid Motion Principles

🔑 Key Concepts & Definitions

• Continuity equation : conservation of mass for steady one-dimensional flow through a duct with one inlet and one outlet

★ Must-know

📐 Formula — For steady incompressible flow without frictional losses, Bernoulli’s equation is $P+\rho gh+\frac{1}{2}\rho v^2=\mathrm{constant}$, relating pressure, elevation, density, and velocity.

📌 In horizontal steady flow of an incompressible fluid, increasing velocity decreases static pressure, while the sum of static and dynamic pressures remains constant.

Further detail

📌 Viscosity is a fluid’s resistance to flow, whereas cohesion is the intermolecular attraction between like molecules that helps water hold together in a drop.

💡 Memory Hook

Bernoulli links pressure and velocity, whereas viscosity resists flow

📖 7. Heart and Blood Circulation

★ Must-know

• The heart pumps blood and nutrients to organs, and synchronized myocardial contraction generates the pressure that drives arterial blood flow.

📌 Blood is not a simple fluid because it contains cells, while arteries and veins are not rigid pipes because their elastic walls change shape in response to fluid forces.

Further detail

• The heart operates at four levels:

  • Organ
  • Tissue
  • Cellular
  • Protein

• L. M. Poiseuille (1799–1869) studied moving fluids in connection with his interest in blood flow through the body.

💡 Memory Hook

The heart acts as a pump connected to elastic vascular pipes containing complex blood

📖 8. Cardiac Function and Turbulence

★ Must-know

📐 Formula — Stroke volume is the difference between left-ventricular end-diastolic volume and end-systolic volume: $SV=EDV-ESV$.

📐 Formula — Ejection fraction is calculated as $EF=\frac{SV}{EDV}\times100$ and is typically between 50 and 80% in humans; readings below this range indicate heart failure.

📐 Formula — Cardiac output is the volume pumped by the heart per minute and is calculated as $CO=SV\times HR$, where HR is heart rate.

• Blood flow is usually laminar in the circulatory system, but it can become turbulent in the aorta when velocity exceeds the critical value of 38 cm/sec for a 2-cm-diameter aorta.

Further detail

• Turbulent-flow noises, called bruits, can be detected with a stethoscope and may indicate abnormalities in the circulatory system.

💡 Memory Hook

SV → EF and CO → flow assessment; excessive velocity → turbulence → bruit

📊 Synthesis Tables

Tonicity effects on cells

Solution	Extracellular osmolarity	Cell response
Hypotonic	Lower than the cell	Water enters; cell expands
Hypertonic	Higher than the cell	Water leaves; cell shrinks
Isotonic	Equal to the cell	No net water movement