Viscosity and Density Relations

Viscosity Measurement

• Viscosity is the resistance to flow under applied stress (pressure).
• The more viscous a liquid is, the more force is required to make it flow at a certain rate.
• The unit of viscosity is poise (P) or dyne.sec/cm².
• 1 poise = 100 centipoise (cP).
• The viscosity of water is 1 cP or 0.01 P.

Intrinsic Viscosity

• Intrinsic viscosity ([η]) is a measure of the viscosity of a polymer solution.
• It is related to the molecular weight (M) of the polymer by the equation [η] = KMα.
• K and α are constants characteristic of the particle-polymer-solvent system.
• The intrinsic viscosity can be used to determine the molecular weight of a polymer.

Radius of Particle Determination

• To determine the radius of a particle, the relative viscosity (ηrel) is plotted against the molar concentration.
• The intercept of the plot is equal to [η]intrinsic.
• The radius of the particle can be calculated from the intrinsic viscosity and molecular weight.

Experiment 5: Boyle's Law

• Purpose: To verify Boyle's Law by measuring the pressure of the atmosphere.
• Apparatus: A glass tube containing mercury.
• Theory: The equation used to find the atmospheric pressure is H = C * (1/L) - B, where H is the length of the mercury column, C and K are constants, L is the length of the tube, and B is the atmospheric pressure.
• Procedure: Measure the scale reading of the mercury levels at different pressures, and plot a graph of H against 1/L.
• The negative intercept on the H-axis is numerically equal to the atmospheric pressure (B).

Experiment 6: Speed of Sound

• Purpose: To determine the speed of sound in a closed resonance tube.
• Apparatus: A closed resonance tube, a meter scale, tuning forks of different frequencies, a rubber pad, and a thermometer.
• Theory: The speed of sound at 0°C is C = C0 * √(273 + t)/273, where C0 is the speed of sound at 0°C, and t is the room temperature.
• The speed of sound can be calculated from the equation C = 2F * (L2 - L1), where F is the frequency of the fork, and L1 and L2 are the lengths of the air column in the tube.
• Procedure: Measure the length of the air column in the tube at different frequencies, and calculate the speed of sound from the equation.

Part II: Viscosity Measurement

• Viscosity is measured using a capillary viscometer.
• The viscosity of a liquid is calculated from the equation η = ηwater * (ρ/ρwater) * (t/twater), where η is the viscosity of the liquid, ρ is the density of the liquid, and t is the time required for the liquid to flow between two marks through a vertical capillary tube.
• The Einstein equation for viscosity is η = η(1 + 2.5 θ), where θ is the volume fraction of the particle.
• θ is related to the concentration of the particle by the equation θ = (volume of particle)/(total volume of dispersion).

Capillary Viscometer

• A capillary viscometer is used to measure the viscosity of a liquid.
• The viscometer consists of a vertical capillary tube of certain diameter.
• The time required for the liquid to flow between two marks through the tube is measured.
• The viscosity of the liquid is calculated from the equation η = ηwater * (ρ/ρwater) * (t/twater).