INCOMPLETE Grade 8 Unit A Test (Section 3-4) Flashcards
Up to 4.1? Review of topics in Unit A slides from sections 3&4. It also has information related to these sections
What is viscosity?
Viscosity is a substance’s resistance to flow. If a substance as a high viscosity it has a low flow rate, and vice versa.
What is flow rate?
How quickly fluids can flow
How is flow rate measured?
Distance over time. For example km/h
What determines the viscosity of a substance?
The internal resistance or friction between the particles of the substance.
What happens if there is more friction between the particles?
It flows slower and has a higher viscosity. In a river, the water at the bottom flows slower because there is friction against water and sand. The water at the top flows faster because there is no friction stopping it.
How does heat in a liquid affect viscosity?
The particles spread, vibrate faster, and have more energy. This extra energy allows the particles to slide over each other more easily.
What is an example of manipulating the viscosity of a substance?
In cold weather, motor oil becomes more viscous. Manufacturers need to make the pipes so that the thicker oil can flow during winter.
What are examples of a more viscous fluid? Less viscous?
Honey is more viscous than water.
What is density?
The amount of matter in a given volume.
True or false: Every substance has the same density
False. Every substance has a different density because they are made of different particles
What do we use to measure density?
A hydrometer
What affects a substance’s density?
The substance being solid or filled with air pockets. (The amount of particles in a given area)
If a substance is less dense than water and is placed on water, will it sink or float?
It will float. If it was more dense than water it would sink.
How do you calculate density?
Density = Mass ÷ Volume
What are the 3 manipulations of the density formula?
D = M/V, M = D×V, V = M/D
Which is the most dense? Solids, liquids, or gases?
Solids are the most dense. Gases are the least dense. Liquids fall in the middle.
Most fluids become denser as they cool down to their freezing temperature. What is the exception?
Water. It reaches its greatest density at 4°C and is 1g/ml
How do you measure density?
In solids it’s g/cm³ or kg/m³. In liquids it’s g/mL.
What is buoyancy?
The tendency of a substance to float
True or false: buoyant objects take up space in a fluid
True
If an object is an a liquid which one has the buoyant force?
The liquid has the buoyant force. The object is pulled down by gravity
What is buoyant force?
A force that acts against the force of gravity (it goes up instead of down).
What is the Plimsoll Line?
It shows how heavy a ship can be safely loaded in different water conditions. It is painted on ships to show the safe water lines in different types of water.
How is buoyant force applied in a hot air balloon?
As the air in the hot air balloon is heated, it becomes less dense than surrounding air and goes up. The buoyant force keeps moving the ballon up until it equals the force of gravity.
What is the Archimedes’ Principle?
The law of buoyancy stating that the buoyant force of an object submerged in fluid is equal to the weight of the fluid that is displaced by that object.
What is compressibility?
The extent to which an object can be compressed
What is compression?
Force acting on an object making it collapse.
What is incompressibility?
An object that cannot be compressed (at all or easily)
Which can be compressed the most? Gases, liquids, or solids?
Gases because they have the most space between the particles.
What is pressure?
The amount of force applied to a given area.
What is pressure measured in?
Pascals or Newtons per m²
What is force?
Force is a push or pull on an object resulting from the interaction between 2 objects
What is force measured in?
Newtons
How many grams is 1 Newton?
1N is around 100g of force (probably don’t need to know)
What are the 3 manipulations of the pressure formula?
P = F÷A, F= P×A, A = F÷P
True or false: the greater the depth of water the greater the pressure
True. It’s like the people tower. The water at the bottom is carrying the weight of the water on the top.
What is Pascal’s law?
Pascal’s law says that when a pressure or force is applied to a confined liquid, the pressure or force is applied equally
What is a hydraulic device?
A device containing liquid to lift heavy objects
True or false: A small force over a large area can create a large force over a small area.
True
What is a pneumatic system?
Basically a hydraulic device but with air or other gases
In what scenario would you use a hydraulic device vs a pneumatic system?
You use hydraulic devices to lift heavy objects. You normally use pneumatic systems to move something quickly rather than lift objects
What is an example of a hydraulic device?
Hydraulic brakes
What is an example of a pneumatic system?
Bicycle pumps
What is solubility?
The ability of a substance to dissolve
What is a detergent?
A detergent is a substance that can remove dirt from fabric
What is a hydrophobic material?
A material that is “afraid of water” and can’t dissolve in it
What are 3 examples of hydrophobic substances?
Fat, dirt, and oils in general
What is a surfactant?
A two-ended molecule with a hydrophobic side and a hydrophilic side.
What is a hydrophilic material?
A material that is “attracted to water” and can be dissolved by it (normally)
What is a micelle?
The sphere the surfactants in dish soap makes when it surrounds grease
How does detergent work on grease?
The surfactants in detergent are one side hydrophilic and one side hydrophobic. The hydrophobic end is attracted to the dirt and they form a sphere around it called a micelle. When exposed to water, the hydrophilic ends make the sphere attracted to water and the dirt gets washed from the fabric and into the water
