Unit A: Sections 3&4 (Grade 8)

Question 1

FLOW

What is flow?

Answer 1

How we describe FLUID (liquids & gases) movement.
- Fluids form a puddle, not a pile
- Movement is continuous and unbroken
- Individual particles can flow past one another

Question 2

FLOW RATE

What is Flow Rate? What is it usually measured in?

Answer 2

The volume of a fluid flowing past a certain point, at a certain time.
- Flow rate decreases as viscosity increases
- Usually measured in L/s
HIGHER Viscosity = SLOWER Flow Rate
LOWER Viscosity = HIGHER Flow Rate

+Something about Planks Constant?

Question 3

FRICTION

What is Friction?

Answer 3

Friction is a force that results when 2 objects rub or touch – CAUSES RESISTANCE
* If the 2 objects are rubbing/touching and go in opposite directions, it is resistance.
* If both object go the in the same direction, it is not resistance.

Question 4

VISCOSITY

What is viscosity and what are the factors that influence it?

Answer 4

• How think/thin a fluid is
• HIGHER Resistance = MORE Viscous
• ~~The greater the rubbing between particles (friction) in any FLUID, the higher the viscosity. Fluids with a higher viscous. don’t flow as easily as fluids with low viscous.~~
• OR A fluids viscosity is determined by it’s internal resistance.
  What affects it:
• Temperature
• Increasing temp = Decreasing viscosity // Decreasing temp. = Increasing Viscosity (- Think Kinetic Energy & Honey -)
• Particle Type - some particles are more prone to resistance than others
  *HIGHER Viscous = SLOWER Flow Rate (Usually Thicker)
  LOWER Viscous = FASTER Flow Rate (Usually more Watery)

Question 5

INTERNAL FRICTION

What is Internal Friction

Answer 5

An internal force that resists the movement between the particles of a material.
OR Friction that keeps a fluid from flowing

Question 6

Simple – DENSITY

What is Density?

Answer 6

Simple Difinition: A property that describes how close together particles in matter are. More dense particles are crowded, whereas less dense particles have more room to move around in.

Question 7

Scientific – DENSITY

Answer 7

Mass per Volume of a substance
MASS - Amount of matter measured in grams (g)
VOLUME - Amount of space occupied. (liquid = mL/ solid = cm3)

Question 8

WATER

What is the density of water?

Answer 8

1g/mL

Question 9

Sink or Float?

How would one determine if an object sinks of floats?

Answer 9

If the density of an object is higher than the density of the fluid ** it’s in, it will *SINK
If the density of an object is lower than the **density of the fluid ** it’s in, it will *FLOAT
—
If the buoyant force is greater than the gravitational force, the object will FLOAT
If the byuoyant force is weaker than the gravitational force the object will SINK

Question 10

DENSITY – LIQUIDS & SOLIDS

What is the difference between units when measuring Liquids and Solids?

Answer 10

Liquids - g/mL or kg/L
Solids - g/cm3

Question 11

CALCULATE DENSITY

How do we calculate density? What is P?

Answer 11

D = m/v
D = Density (example: 19.3 g/mL)
M = Mass (g/kg)
V = Volume (Liquids = mL/L, Solids = g/cm3)

p (for density) is greek for rho

Do the triangle method in emergencies

Question 12

DENSITY + PARTICLE MODEL OF MATTER

Which states of matter are least/most dense? What affects density? Why?

Answer 12

• Different substances have different sized particles
• This can affect how many can ‘fit’ in a volume
• More space between particles the lower the density.
  States of matter and their density: The more space between particles indicates a lower density.
• Solids = More Dense
• Liquids = Moderate
• Gas = Least Dense

Exception: WATER

Question 13

DENSITY & TEMPERATURE

Answer 13

As temperature increases, density decreases.
- As temp. increases, particles move faster
- As particles move faster, they move further apart
- As space increases between particles increases, density decreases.
Density does not change as long as the temperature stays consistent

Question 14

SALT vs FRESH WATER

Are you most likely to float in salt or fresh water? Why?

Answer 14

Water on it’s own has the density of 1 g/mL.
Remember: density is affected by temperature, but also the partticles within it (concentration!).
Adding salt = adding particles (more particles = more mass)
Result: Density Increases

Question 15

BUOYANCY

What is buoyancy?

Answer 15

The tendancy to float when placed in a fluid.
NOTE: There are always 2 Forces acting upon an object when in a fluid:
- Gravity: Pushes DOWN on an object (of the gravity is greater than the buoyant force, the object will SINK)
- Buoyant Force: Pushes UP on an object (if the buoyant force on an object is greater than the gravity, the object will FLOAT)

Question 16

Examples of Buoyancy

What are some applicants of buoyancy we use in our daily lives?

Answer 16

• Buoy
• Ship
• etc…

Question 17

COMPRESSIBILITY

What is compressibility?

Answer 17

When a force pushes on an object, the object is said to be under compression. Objects under compression tend to deform in shape.
Think of kicking a soccer ball, your foot is compressing the fluid (air) within the ball

Question 18

COMPRESSION – GASES vs LIQUIDS

Is it easier to compress an empty bottle or one filled with water?

Answer 18

The empty one!
Gases can be compressed more than liquids because gases have more space to waste.
Expand? In a gas, there are less particles so they have space to be compressed.
Liquids however, are said to be INCOMPRESSIBLE. - Liquid particles don’t have anywhere to go

Think of the pistons in science class with Ms. Johnson

Higher Volume = Low Pressure – High Pressure = Smaller Volume

Question 19

Pressure

What is pressure?

Answer 19

Pressure is the amount of force aplied to a given area.
More Force = More Pressure
Area Increases = Pressure Decreases
Area Decreases = Pressure Increases

Think: What hurts more? Being punched hard or soft?

Question 20

Blaise Pascal

Who was this guy?

Answer 20

Simple Definition: An intelligent mathematician who originated from the 1600s. He created the concept of pressure. His name was Pascal
In-Depth Definition: Blaise Pascal was a French Mathematician who was curious about fluids and preformed some experiments.

Question 21

Calculate Pressure

Answer 21

P = F/A
P = Pressure (Pa)
F = Force (N)
A = Area (~m2)

(~) is usually

Question 22

Pressure - Water Bottle & The 3 holes

Answer 22

You have a water bottle with 3 holes. One at the top, bottom, and one in the middle. Where will the water come out with more pressure?
A: The bottom hole.
Why? The water lower down has all the weight of the water above pushing down on it. In other words: it has more force pushing it down
More force = more pressure

Greater depth = greater pressure

Question 23

Pascal’s Law

What was Pascal’s Law

Answer 23

Pressure applied to a fluid in a closed system will be transmitted throughout the fluid at the same strength.

Pressure will push on all sides of the container at right angles.

Question 24

Hydraulic Devices

What is a hydraulic device?

Answer 24

A hydraulic device uses LIQUID
- Uses 2 pistons of different sizes
- Small piston = input (pushes down on liquid to create pressure)
- The pressure is transmitted through the liquid and pushes up on the large piston
- Big Piston = output
- The big piston has a much larger area, but, the pressure is the same throughout the whole system.

Question 25

Pneumatic Devices

What are Pneumatic Devices?

Answer 25

Pneumatic Devices use compressed AIR to do tasks.
Examples: Dentist drills, Jack hammers, paint sprayers, air brakes, pumps/compressor
Summary: Basically the same as hydraulic systems exept pneumatics use air.

Question 26

Detergents

What are detergents? How are they used? What do they do?

Answer 26

• Most detergents are liquids/powders that can dissolve in water
• The contain cleaning agents called surfactants

Question 27

Surfactants

What are surfactants? What does the word mean? What are it’s parts?

Answer 27

Surfactants are particles that attach themselves to dirt and oils seperating them off your clothing. When the detergent particle surrounds the dirt, is forms a sphere.
SURFACTANT – Surface Active Agents
Surfactents are made up of 2 parts: 1) The ‘ball’ is hydrophilic, the ‘string’ is hydrophobic
Once the detergent has set into the dirt, it seperates into the water.

Question 28

Surfactants - Hydrophilic vs Hydrophobic

What are they? How do they work?

Answer 28

Hydrophillic – loves water
Hydrophobic – hates water
The hydrophobic part of the detergent particle latches onto the dirt.
The hydrophillic part (sphere) is attracted to the water.

Question 29

SCUBA

Answer 29

Self
Contained
Underwater
Breathing
Apparatus

Question 30

Diving and Decompression

Answer 30

A SCUBA consists of air tanks and regulators to maintain the flow of the air. Deep in water, nitrogen dissolves in our blood at much higher concentrations than normal.

Question 31

“The Bends”

What are the bends? How do they occur? How can we get rid of it?

Answer 31

If the diver ascends too quickly, the pressure decreases rapidly and the diver can get sick with “the bends”. Why?
- Nitogen leaks out of the blood tissue and bubbles collect. This put’s the diver at risk of death
- The decompression chamber is used to decrease the pressure of the diver very slowly until better.

Question 32

1 Rule of Scuba Diving?

A little off topic, but what is the #1 rule of Scuba Diving?

Answer 32

Never hold your breath while diving
- The deeper you dive, the higher atmoshphere you’re in

An Atmpsphere (ATM) is a unit to measure ambient pressure

Question 33

Pumps

What is a pump? Example?

Answer 33

A device that moves fluid through or into something.
Example: Bike Pump - This has a piston that moves up in a cylinder by letting air in. By pushing the piston down, the air is compressed and the pressure increases letting the air out of the small hole at the BOTTOM.

Remember: The greater the depth, the greater the pressure

Question 34

Pipeline Pigs

What are pipleine pigs? How are they used?

Answer 34

Pipeline pigs are computerized units placed in pipelines get pushed by the moving gas through the pipes and through the country
It can clean the pipes with brushes as it moves through and the sensors can check that the pipe is still in good condition

In my words, it’s a -national- giant filter

Question 35

Valves

Answer 35

Valves are devices to control or regulate the amount of flow
Valves can either turn on and off or control the level of fluid in a container
EXAMPLE: The ball valve (eg. hose) is a valve that works when turned in different directions (on & off type). When turned one way, the hose will turn on; when turned in another, it’ll turn off

Question 36

Submarine

How does a submarine work?

Answer 36

• When on surface, ballast tanks are empty
• To dive, the submarine releases air from the ballast tanks and valves open to let some water in.
• To resurface To resurface a compressed air tank located inside the sub fills up the ballast tank forcing the water out!

Question 37

Fish Bladder

Answer 37

Fishies use a swim bladder that allows dissolved gases to move in and out of the sac. This regulates the amount of buoyancy.
- FLOAT/UP: Swim bladder muscles relax. Gets bigger, fish is lighter
- SINK/DOWN: Muscles tightesn, bladder small
- Hover: Bladder muscles tighten, gets smaller, floats legs until fish hovers weightless.