8.3 Viscosity and Surface Tension

• Fluids with high viscosity flow slowly and have a thick, syrupy consistency
• How does temperature affect viscosity?

  Colder increases viscosity
• Why does honey have higher viscosity than water?

  Complex molecules, lower temperature
• Which fluid has higher viscosity: honey or water?

  Honey
• Honey has a higher viscosity than water because it contains larger molecules
• What is fluid resistance directly related to?

  Viscosity
• The viscous drag force is given by the equation $F_{d} =$$6\pi\eta rv$, where η is the viscosity
• Cohesive forces minimize surface area
• What is surface tension?

  Force along fluid surface
• Surface tension results from the balance between cohesive and adhesive forces.
• What is viscosity?

  Resistance to flow
• Higher temperature increases viscosity.

  False
• In the viscous drag equation, η represents the viscosity of the fluid.
• Match the meniscus type with its shape:

  Concave ↔️ Curves upward

  Convex ↔️ Curves downward
• What happens to viscosity as temperature increases?

  Decreases
• Order the following factors based on their effect on viscosity, from highest to lowest.

  1️⃣ Complex molecular structure

  2️⃣ Lower temperature

  3️⃣ Higher temperature
• Match the factor with its effect on viscosity:

  Temperature ↔️ Decreases viscosity

  Molecular Structure ↔️ Increases viscosity
• Honey exhibits greater fluid resistance than water due to its higher viscosity and cooler storage temperatures.

  True
• The viscous drag force opposes the motion of an object moving through a fluid
• Surface tension is the force acting along the surface of a liquid, causing it to behave like an elastic sheet
• The interplay between cohesive and adhesive forces determines the surface tension of a liquid.


  True
• Water rising through plant stems is an example of capillary action.


  True
• Honey has a higher viscosity than water because it is stored at lower temperatures.


  True
• Fluid resistance refers to the opposition a fluid encounters during flow
• Viscous drag increases with higher viscosity, larger object size, and greater velocity.


  True
• Match the type of force with its effect on surface tension:

  Cohesive forces ↔️ Minimizes surface area

  Adhesive forces ↔️ Spreads or sticks to surfaces
• The meniscus is the curved surface formed at the surface of a liquid in a container
• A concave meniscus occurs when adhesive forces are stronger than cohesive forces.


  True
• Capillary action is the ability of a liquid to flow in narrow spaces against gravity
• What is viscosity a measure of?

  Resistance to flow
• Viscosity is affected by temperature and molecular structure.


  True
• Complex, large molecules lead to higher viscosity
• Factors affecting viscosity in order of importance

  1️⃣ Temperature

  2️⃣ Molecular Structure
• Honey is stored at a colder temperature, contributing to its higher viscosity.


  True
• What are the two key factors affecting viscosity?

  Temperature and molecular structure
• High viscosity fluids have greater fluid resistance.


  True
• Match the factor with its effect on viscous drag:

  Fluid Viscosity ↔️ Higher viscosity increases drag

  Object Size ↔️ Larger objects experience more drag

  Relative Velocity ↔️ Higher velocity increases drag
• What is surface tension caused by?

  Cohesive and adhesive forces
• What is the consistency of fluids with low viscosity?

  Thin, watery
• Cohesive forces minimize surface area.


  True