Liquids

Question 1

cohesion

Answer 1

the attraction force between molecules of the same substance

an intermolecular attraction

the formation of water droplets on the surface tension of a liquid due to cohesion

For Example:

water droplets sticking to each other

Question 2

adhesion qualities

Answer 2

the attraction force between different molecules

an intramolecular attraction

the spreading of liquid on a solid surface is due to adhesion

For example:

water sticks to other things

Question 3

Capillary action

Answer 3

caused by the adhesive, cohesive and surface tension forces

allows a thin film of liquid to be drawn up the sides of a glass tube or forced down the tube, depending on the liquid being used

considered when designing and developing many commercial products – lamp oils and lamp wicks

nature displays capillary action when water rises in soil and maple sap flows in a tree and the circulation of blood in your body

Question 4

What determines the degree of capillary action?

Answer 4

depends on what the material is made of, its shape and cellular structure

for example:

the height water can be raised in a glass tube depends on the diameter of the tube

Question 5

meniscus

Answer 5

the curve formed by capillary action

Question 6

molecules that demonstrate greater cohesion than adhesion will..

Answer 6

fall in a capillary tube/graduated cylinder

a smile!

Question 7

molecules that demonstrate greater adhesion than cohesion will…

Answer 7

rise in a capillary tube/graduated cylinder

a frown!

Question 8

cohesive forces

Answer 8

forces of attraction between molecules that are alike

gives solids rigidity and strength

cause a greater attractive force between molecules at the surface of the material

Question 9

adhesive forces

Answer 9

forces of attraction between unlike molecules

glue can supply the adhesive forces used in binding surfaces together

pencil lead, ink, chalk and paint

Question 10

What is the difference between cohesion and adhesion?

Answer 10

They are nouns that describe the state of molecules sticking together.

Adhesion refers to clinging of unlike molecules and cohesion refers to the clinging of like molecules

Cohesion is the tendency of water molecules to stick to other water molecules while adhesion is the tendency of water to stick to other substances

Question 11

surface tension

Answer 11

cohesive forces between molecules of the same material cause a greater attractive force between molecules at the surface of the material

causes dewdrops, raindrops, and soap bubbles to form a sphere

detergents break down the surface tension and permit the direct to be washed away

Question 12

Why does a meniscus form a larger surface area?

Answer 12

molecules on the surface are spread

their cohesive forces create the tension on the surface of the liquid

This tension creates an “elastic skin” known as surface tension!

Question 13

volatility

Answer 13

the ability of a liquid to be changed to a vapor

Question 14

vapor

Answer 14

the word used to describe the molecules of a liquid that escape the surface of the liquid and form a gas

Question 15

Why does gas have octane ratings?

Answer 15

describes the ability of the fuel to vaporize and burn inside an automobile engine

the lower the octane, the more volatile the gasoline

pings and knocks indicate the fuel is not burning correctly

Question 16

Why must more volatile liquids have greater care?

Answer 16

volatile liquids burst into flames easily

they displace the oxygen in the air we breath

Question 17

Viscosity

Answer 17

the ease in which a liquid flows

Question 18

A fluid that has high viscosity does not..

Answer 18

flow easily

there is more friction between the molecules of the fluid which slows its flow

Question 19

Why is viscosity an important characteristic when developing and using lubricating oils?

Answer 19

The higher viscosity of the lubricating oil helps prevent wear on the internal parts of the engine

Question 20

How do you measure viscosity of a fluid?

Answer 20

measuring the time required for a given amount of fluid to pass through a long tube of a small diameter

the longer the time, the higher the viscosity rating

viscosity ratings are expressed in weight

an example would be the level of 40 weight oil
an oil with a higher viscosity rating will have a higher weight assigned to it

Question 21

Specific gravity

Answer 21

the ratio of the weight of a liquid to the weight of an equal volume of water

important when checking:

• antifreeze
• gas
• alcohols
• acids

indication that the correct amount of chemical is in the liquid

Question 22

hydrometer

Answer 22

easiest way to check the specific gravity of liquids

the greater the specific gravity of the liquid, the higher the float in the hydrometer will rise

Question 23

specific gravity formula

Answer 23

weight of liquid / weight of equal volume of water

Question 24

Pascal’s law

Answer 24

pressure is instantly transmitted throughout a liquid

if you change pressure at any point in a fluid container, it equalizes itself across all the fluid

Squeeze one point of water in a balloon and the pressure evens itself out across the whole water balloon

Question 25

Hydraulic press

Answer 25

takes advantage of Pascal’s law

extreme pressure can be exerted with a small effort

the pressure generated by the small piston exerts a force on the larger piston equal to the ratio of the areas of the pistons

force 2 = area 2 x force 1 / area 1

Question 26

Hydraulic system equation

Answer 26

force 2 / area 2 = force 1 / area 1

force is in reference to the force being applied and area is referring to the space in which the force is pushing upon

Question 27

Buoyancy

Answer 27

the force of a liquid which pushes an object up

Question 28

Archimedes

Answer 28

discovered buoyancy

when a body is placed in a fluid, it is buoyed up by a force equal to the weight of the displaced fluid

in order for an object to float in water, the buoyancy force must be equal to the entire weight of the object

Question 29

Why do steel ships float?

Answer 29

They enclose a large volume of space

The density of the entire ship is less than the density of the water