Download Factors Affecting Viscosity

Viscosity Chapter 7
Particles in Solids, Liquids, and Gases.
Shape and volume
Space between
particles
Movement
Attraction Forces
Solid
Definite shape and
volume
Very little space
between particles
Very little movement of
particles
Strong attraction forces
between particles
Liquid
No definite shape but a
definite volume
Moderate space
between particles
Moderate movement of
particles
Moderate attraction
forces
Gas
No definite shape or
volume
Large space between
particles
More freedom of
movement
Weak attraction forces
Fluids are liquids and gases because they have more movement and the particles are not held so tightly
by attraction forces so that the particles can slip past one another and flow.
A fluid is anything that flows.
Changes of State
Melting ( solid to a liquid) - add heat energy
Freezing (liquid to a solid) – take away energy
Condensation (gas to a liquid) – take away energy
Evaporation (liquid to a gas) - add heat energy
Sublimation (solid to a gas) - add heat energy
Deposition (gas to a solid) – take away energy
Melting
Solid
--------------- Add energy (heat)-----------------
Liquid
Little spaces
moderate spaces
Little movement
moderate movement
Strong attraction
moderate attraction
Adding energy causes the particles to speed up, they collide more often and harder causing them to
spread out, which in turn decreases the attraction forces. This is how the solid takes on the properties
of a liquid.
Freezing
Liquid --------------- take away energy (cool it down) --------------- Solid
moderate spaces
Little spaces
moderate movement
Little movement
moderate attraction
Strong attraction
Taking away energy causes the particles to slow down, they collide less often , they come closer
together, because they are closer together their attraction forces are greater. A liquid will then take on
the properties of a solid.
All the changes of states can be explained in this way. You could be asked to explain either one.
Viscosity
-describes the thickness or thinness of a fluid.
- is a fluids resistance to flow
- high resistance means it is thick, it has a high resistance to flow
high viscosity = thick
- low resistance means it is thin, it has a low resistance to flow low viscosity = thin
Importance of Viscosity
-
Affects the food we eat, your mouth is highly sensitive to viscosity.
Affects the products we buy You do not want paint that is too thin or thick etc
Viscosity and Flow Rate
Flow rate is how fast or slow a fluid flows or travels from point A to point B.
If a fluid is thick HIGH VISCOSITY = LOW FLOW RATE
If a fluid is thin LOW VISCOSITY = HIGH FLOW RATE
Example: molasses which is thick (high viscosity) will travel slowly (low flow rate)
Water which is thin (low viscosity) will travel fast (high flow rate)
Flow rate =
Distance travelled
Time taken to travel
=
cm/s
Factors Affecting Viscosity
Temperature (Liquids)
Temperature (gases)
Concentration
Attraction Forces
Size and complexity of the particle
Temperature increases, viscosity decreases
-particles have more energy and this decreases the
attraction forces allowing them to slip past one another
more easily (ex: heat up honey and it moves faster)
Temperature decreases, viscosity increases
Temperature increases, viscosity increases
Gases do not depend on a energy to move further
apart- adding energy only increases the number of
collisions between particles and therefore increases
internal friction.
Temperature decreases, viscosity decreases
Cooler air is thinner.
Concentration increases, viscosity increases
The greater the number of particles per volume the
greater the internal friction and viscosity.
Add flour to gravy to make it thicker.
Concentration decreases, viscosity decreases
Attraction forces decrease, viscosity decreases
Easier for particles to slide past one another.
Attraction forces increases, viscosity increases
Bigger, more complex, higher the viscosity
The bigger the particle, the more complex it is and
therefore the harder it is to slip past one another.
Smaller, less complex, lower the viscosity