EONS LEARNING

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      • Study Skills
      • Periodic Table
      • Common Ion Sheet
      • The Scientific Method
      • Doing Background Research
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    • Unit 1: Beginning Chemistry >
      • Lesson 1: The Atom >
        • What is an Atom?
        • The Structure of Atoms
        • The Periodic Table
        • Modeling Atoms
      • Lesson 2: Chemical Bonding >
        • Why Do Atoms Form Bonds?
        • Ionic Bonding
        • Covalent Bonding
        • Intermolecular Attraction
      • Lesson 3: Chemical Nomenclature >
        • Octet Rule
        • Ionic Compounds
        • Covalent Molecules
      • Lesson 4: Molecular Molecules >
        • Modeling Ionic Compounds
        • Modeling Covalent Molecules
      • Lesson 5: States of Matter >
        • States of Matter
        • Phase Changes
      • Lesson 6: Density >
        • What is Density?
        • Calculating Density
      • Lesson 7: Thermodynamics >
        • Temperature
        • Heat
        • Gas Laws
      • Lesson 8: Solution Chemistry >
        • Diffusion
        • Solutions and Molarity
        • Semi-Permeable Membranes
      • Lesson 9: Thermal Expansion >
        • Thermal Expansion
    • Unit 2: Earth Science >
      • Lesson 10: Earth at a Glance >
        • Perspective
        • Maps
      • Lesson 11: Layers of the Earth >
        • Layers of the Earth
      • Lesson 12: Plate Tectonics >
        • Plate Tectonics
      • Lesson 13: Rocks and Minerals >
        • Rocks and Minerals
      • Lesson 14: Particle Sorting >
        • Differentiation
        • Deposition of Sediment
      • Lesson 15: The Atmosphere >
        • Composition of the Atmosphere
        • Layers of the Atmosphere
        • Change Over Time
        • Atmospheric Disruption
    • Unit 3: The Cell >
      • Lesson 16: Life >
        • What is Life?
        • Structural Hierarchy of Living Things
      • Lesson 17: Biochemistry >
        • Intro to Biochemistry
        • Water
        • Micromolecules
        • Energy, Carbohydrates, Lipids
        • Protein and Nucleic Acid
      • Lesson 18: Cells >
        • What are Cells?
        • Microscopy
        • Plant and Animal Cells
      • Lesson 19: Membrane Transport >
        • A Special Environment
        • The Structure of Membranes
        • Membrane Transport
      • Lesson 20: Energy and Cell Respiration >
        • Energy in Biology
        • Energy Diagrams
        • Glycolysis and Anaerobic Respiration
        • Aerobic Cellular Respiration
      • Lesson 21: Photosynthesis >
        • Plants Get Energy From The Sun
        • Photosynthesis Process
        • Energy, Ecosystems, and the Environment
    • Unit 4: Anatomy and Physiology >
      • Lesson 22: The Human Body >
        • What Are Bodies Made Of?
        • What Do Bodies Do?
      • Lesson 23: The Nervous System >
        • The Nervous System
        • Neuronal Communication
        • The Central Nervous System
      • Lesson 24: The Endocrine System >
        • The Endocrine System
        • Hormones
        • Hormones, Puberty, and Reproduction
      • Lesson 25: The Integumentary System >
        • The Integumentary System
      • Lesson 26: The Musculoskeletal System >
        • The Skeletal System
        • The Muscular System
        • Anatomy Of The Musculoskeletal System
      • Lesson 27: The Cardiovascular System >
        • Blood and Blood Vessels
        • The Heart
      • Lesson 28: The Respiratory System >
        • The Respiratory System
      • Lesson 29: The Digestive System >
        • The Digestive System
        • Nutrition
      • Lesson 30: The Excretory System >
        • The Excretory System
      • Lesson 31: The Immune System >
        • Disease and Infection
        • Immunity
    • Units 5-6 Coming Soon
  • Workbench
    • Unit 1 >
      • EIS >
        • Lesson 1: Atoms
        • Lesson 2: Chemical Bonding
        • Lesson 3: Chemical Nomenclature
        • Lesson 4: Molecular Models
        • Lesson 5: States of Matter
        • Lesson 6: Density
        • Lesson 7: Thermodynamics
        • Lesson 8: Solution Chemistry
        • Lesson 9: Thermal Expansion
      • Unit 1: Project
      • Unit 1: Exam Review
      • Unit 1: Exam
    • Unit 2 >
      • EIS >
        • Lesson 10: Earth at a Glance
        • Lesson 11: Layers of the Earth
        • Lesson 12: Plate Tectonics
        • Lesson 13: Rocks and Minerals
        • Lesson 14: Particle Sorting
        • Lesson 15: The Atmosphere
      • Unit 2: Project
      • Unit 2: Exam Review
      • Unit 2: Exam
    • Unit 3 >
      • EIS >
        • Lesson 16: Life
        • Lesson 17: Biochemsitry
        • Lesson 18: Cells
        • Lesson 19: Membrane Transport
        • Lesson 20: Energy and Cell Respiration
        • Lesson 21: Photosynthesis
      • Unit 3: Project
      • Unit 3: Exam Review
      • Unit 3: Exam
    • Unit 4 >
      • EIS >
        • 22: The Human Body
        • 23: The Nervous System
        • 24: The Endocrine System
        • 25: The Integumentary System
        • 26: The Musculoskeletal System
        • 27: The Cardiovascular System
        • 28: The Respiratory System
        • 29: The Digestive System
        • 30: The Excretory System
        • 31: The Immune System
      • Unit 4 Project
      • Unit 4 Exam Review
      • Unit 4 Exam
    • Units 5-6 Coming Soon
  • Donate
  • Home
  • About Us
  • Classroom
    • Resources >
      • Study Skills
      • Periodic Table
      • Common Ion Sheet
      • The Scientific Method
      • Doing Background Research
    • Introduction and Course Philosophy
    • Unit 1: Beginning Chemistry >
      • Lesson 1: The Atom >
        • What is an Atom?
        • The Structure of Atoms
        • The Periodic Table
        • Modeling Atoms
      • Lesson 2: Chemical Bonding >
        • Why Do Atoms Form Bonds?
        • Ionic Bonding
        • Covalent Bonding
        • Intermolecular Attraction
      • Lesson 3: Chemical Nomenclature >
        • Octet Rule
        • Ionic Compounds
        • Covalent Molecules
      • Lesson 4: Molecular Molecules >
        • Modeling Ionic Compounds
        • Modeling Covalent Molecules
      • Lesson 5: States of Matter >
        • States of Matter
        • Phase Changes
      • Lesson 6: Density >
        • What is Density?
        • Calculating Density
      • Lesson 7: Thermodynamics >
        • Temperature
        • Heat
        • Gas Laws
      • Lesson 8: Solution Chemistry >
        • Diffusion
        • Solutions and Molarity
        • Semi-Permeable Membranes
      • Lesson 9: Thermal Expansion >
        • Thermal Expansion
    • Unit 2: Earth Science >
      • Lesson 10: Earth at a Glance >
        • Perspective
        • Maps
      • Lesson 11: Layers of the Earth >
        • Layers of the Earth
      • Lesson 12: Plate Tectonics >
        • Plate Tectonics
      • Lesson 13: Rocks and Minerals >
        • Rocks and Minerals
      • Lesson 14: Particle Sorting >
        • Differentiation
        • Deposition of Sediment
      • Lesson 15: The Atmosphere >
        • Composition of the Atmosphere
        • Layers of the Atmosphere
        • Change Over Time
        • Atmospheric Disruption
    • Unit 3: The Cell >
      • Lesson 16: Life >
        • What is Life?
        • Structural Hierarchy of Living Things
      • Lesson 17: Biochemistry >
        • Intro to Biochemistry
        • Water
        • Micromolecules
        • Energy, Carbohydrates, Lipids
        • Protein and Nucleic Acid
      • Lesson 18: Cells >
        • What are Cells?
        • Microscopy
        • Plant and Animal Cells
      • Lesson 19: Membrane Transport >
        • A Special Environment
        • The Structure of Membranes
        • Membrane Transport
      • Lesson 20: Energy and Cell Respiration >
        • Energy in Biology
        • Energy Diagrams
        • Glycolysis and Anaerobic Respiration
        • Aerobic Cellular Respiration
      • Lesson 21: Photosynthesis >
        • Plants Get Energy From The Sun
        • Photosynthesis Process
        • Energy, Ecosystems, and the Environment
    • Unit 4: Anatomy and Physiology >
      • Lesson 22: The Human Body >
        • What Are Bodies Made Of?
        • What Do Bodies Do?
      • Lesson 23: The Nervous System >
        • The Nervous System
        • Neuronal Communication
        • The Central Nervous System
      • Lesson 24: The Endocrine System >
        • The Endocrine System
        • Hormones
        • Hormones, Puberty, and Reproduction
      • Lesson 25: The Integumentary System >
        • The Integumentary System
      • Lesson 26: The Musculoskeletal System >
        • The Skeletal System
        • The Muscular System
        • Anatomy Of The Musculoskeletal System
      • Lesson 27: The Cardiovascular System >
        • Blood and Blood Vessels
        • The Heart
      • Lesson 28: The Respiratory System >
        • The Respiratory System
      • Lesson 29: The Digestive System >
        • The Digestive System
        • Nutrition
      • Lesson 30: The Excretory System >
        • The Excretory System
      • Lesson 31: The Immune System >
        • Disease and Infection
        • Immunity
    • Units 5-6 Coming Soon
  • Workbench
    • Unit 1 >
      • EIS >
        • Lesson 1: Atoms
        • Lesson 2: Chemical Bonding
        • Lesson 3: Chemical Nomenclature
        • Lesson 4: Molecular Models
        • Lesson 5: States of Matter
        • Lesson 6: Density
        • Lesson 7: Thermodynamics
        • Lesson 8: Solution Chemistry
        • Lesson 9: Thermal Expansion
      • Unit 1: Project
      • Unit 1: Exam Review
      • Unit 1: Exam
    • Unit 2 >
      • EIS >
        • Lesson 10: Earth at a Glance
        • Lesson 11: Layers of the Earth
        • Lesson 12: Plate Tectonics
        • Lesson 13: Rocks and Minerals
        • Lesson 14: Particle Sorting
        • Lesson 15: The Atmosphere
      • Unit 2: Project
      • Unit 2: Exam Review
      • Unit 2: Exam
    • Unit 3 >
      • EIS >
        • Lesson 16: Life
        • Lesson 17: Biochemsitry
        • Lesson 18: Cells
        • Lesson 19: Membrane Transport
        • Lesson 20: Energy and Cell Respiration
        • Lesson 21: Photosynthesis
      • Unit 3: Project
      • Unit 3: Exam Review
      • Unit 3: Exam
    • Unit 4 >
      • EIS >
        • 22: The Human Body
        • 23: The Nervous System
        • 24: The Endocrine System
        • 25: The Integumentary System
        • 26: The Musculoskeletal System
        • 27: The Cardiovascular System
        • 28: The Respiratory System
        • 29: The Digestive System
        • 30: The Excretory System
        • 31: The Immune System
      • Unit 4 Project
      • Unit 4 Exam Review
      • Unit 4 Exam
    • Units 5-6 Coming Soon
  • Donate

Differentiation

Particle sorting: we’ve talked about it before, we just haven’t put a name to it yet. Quite simply, particle sorting describes how “stuff” (in this lesson, we’ll mainly talk about rocks) are separated based on their density and size. This process is known also known as differentiation. 

If you can follow, this guy will shout basically everything you need to know about particle sorting:
​

​Particle sorting/differentiation describes how quickly things will sink in still water. It can be a bit tricky to wrap your mind around because it seems to contradict itself. These are the two main rules that dictate how it occurs:
  1. Dense stuff sinks.
  2. Small stuff sinks.

We’ll go through each of these to explain where this contradiction comes from, and we’ll then look at the example of gold panning to see how each becomes important in a real-world context.

Dense Stuff Sinks

If we consider these rules separately, both make perfect sense. We know that heavy stuff sinks because we can see it happen. We can see a rock sink in water. We can see oil float on water. We also know that the layers of the Earth are the way they are because the densest stuff (iron) sank to the middle. In fact, if we could somehow magically make all particles the same size, we would see the heavy stuff settle to the bottom every time. For example, if we put baseballs in a ballpit and shook it around a bit, we would quickly see the baseballs settle to the bottom, like so:
Picture
This is especially true in water and other liquids (versus gases/air), where the buoyant force is more significant and the difference between how lighter things and heavier things get affected by that force is greater. But, the same still holds true as long as a buoyant force exists. We’re not super worried about you understanding the precise physics of this for this class, but, if you’d like a little more explanation, this video gives a great overview of buoyancy:

​We’re mainly interested in the takeaway here, which should be pretty obvious to you based on what you learned about density in Chemistry: Denser things sink faster than less dense things.

Small Stuff Sinks

But, that’s not the full story, because we also know that small stuff sinks. For example, if we put sand in a jar of rocks, the sand would fall in between the cracks to the bottom. Or, if we put salt on popcorn, the salt will fall to the bottom, and we still have bland popcorn. If we completely control for density (make everything the same), this will always be the case: the small stuff will sink.
Picture
Separately, those two ideas should be pretty easy to wrap your head around. When we put them together, though, things might get a bit confusing. After all, we usually associate the heaviest stuff with the biggest stuff. But, remember, this is about density, not weight. And density is weight (mass) divided by volume: it takes size into account. So, something “light” could actually be quite dense, if it’s small. Be sure you understand the difference between density and mass.

Even if you do understand this idea, dense stuff can be big and non-dense stuff can be small. The real world isn’t a perfect system like our examples were. That can happen. So, let’s look at a few real world examples to understand particle sorting better.

Panning for Gold

Let’s start with a little history lesson. In 1849, courageous (or, if you prefer, foolish) Americans “rushed” to California in a maniacal gold craze: the Gold Rush of 1849. 
Picture
Very few would be successful, but these guys are clearly super excited about their panning (okay, you can’t really tell because everything is black or white and their mustaches cover their mouths, but they are SO excited). 

The pans the men are holding show you how particle sorting works in real life. To find small deposits of gold in the river, the guys would scoop a pan full of sediment, then shake the pan until, magically, the only particles left over were gold particles. They would usually only find tiny bits of gold dust, but, just like a drop of water may lead back to the Niagara, these little bits could lead them to the “gold vein,” and they would make it RAIN! 

Watch this guy explain how to pan for gold:
I’ll go into a little more detail now.

You know that items denser than water will sink and items less dense than water will float. Every particle in sediment (that’s a fancy word for dirt and rocks) is denser than water. But, they’re not necessarily the same density as each other. Gold, for example, is denser than most rocks. When we sort particles, we take advantage of their density and basically make them race to the bottom of the pan whenever we shake it. Let’s take a look. 
Picture
Here are some particles in water. Gold is colored in gold, because gold is gold and that’s the goldiest of the golds. Right now, they’re arranged randomly, just sitting around until we shake the pan. To see what happens when we shake the pan, let’s pretend like they all had a fair start, like so:
Picture
Based on what you know about particle sorting already, can you guess what happens next?
Picture
You guessed it! (Probably). Gold, with the greatest density, falls the fastest. 

Now imagine that the gold was really big and everything else was tiny:
Picture
This time, the gold is fatter, and therefore slower (remember that small stuff sinks faster). There are two reasons that gold might not “get the gold” in this race:
  1. Other particles might get in its way, because it is so big.
  2. It might get slowed down by that buoyant force thingy I mentioned. (Don’t worry too much about the details, but I’ll tell you anyways: buoyant force pushes up on stuff based on its volume. Bigger stuff gets pushed up more by water. That’s why ships can float even though they’re made of metal.) 

Let’s see what happens when gold, the dense stuff, is REALLY BIG and the other stuff is REALLY SMALL. 
Picture
Buoyant force pushes up on the gold SO MUCH because it is SO BIG that it doesn’t win the race to the bottom. In terms of gold panning, this isn’t really a big deal, because, if the gold were that big, the panner would just be able to pull it out and sell it for lots of money. 

We could calculate the exact size that this gold would have to be, based on its density and the size and density of the other particles in suspension, for it to lose this race. In other words, we could determine exactly how big our gold fragment had to be before panning would no longer be useful. But, that’s some pretty complicated math, which is a little above your current learning level, so I’ll let you learn about that when you’re older, smarter, and know more about Newtonian physics.

Summary

You should understand:
  • That dense stuff sinks.
  • That small stuff sinks.
  • That these two rules sometimes contradict each other, in which case we’d have to do an experiment (or do math, which we won’t in this course) to figure out which actually occurs.

Learning Activity

Picture
Next: Deposition of setiment

Content contributors: Emma Moulton and Emily Zhang
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