Google Classroom Assignment
Read the Layers of the Earth webpage first to refresh your memory about what we covered in class. Then read and do the interactives on this webpage. Go to Google Classroom to answer the questions on the right.
Things you should know about matter, gravity and density
- Matter is something that has mass and occupies space
- Mass is the amount of matter in an object.
Mass is NOT weight, although we often talk about something being heavier if it has more mass. To know how they are different, you have to learn about gravity first.
- Gravity is the force of attraction between two objects with mass. The larger the mass, the greater the gravitational force. And the greater the distance between the objects, the lesser the gravitational force.
That means that all objects attract each other. The more massive (use the words, 'more massive' because 'bigger or larger' can imply a bigger volume rather than greater mass) and closer the object, the greater the attraction. That's why an apple falls to the earth. The Earth is very massive and attracts the apple, you, trees and even the air to it. Gravity pulls inward towards the center of the object (the center of gravity), so the closer (shorter distance) you are to the center of gravity, the greater the gravitational force.
- Weight is the amount of matter (mass) multiplied by gravity (or the amount of force with which an object is attracted to the Earth).
When you stand on a scale, it is actually measuring the gravitational force of attraction between the Earth and the object (you) that is standing on it. The more massive you are, the greater the gravitational force between you and the Earth, so you weigh more! Because Earth is a more massive object than the Moon, our apple would weigh more on Earth than it does on the less massive moon. And if you were to go out into space where the gravitational force is extremely weak because of the increased distance between you and the massive Earth (or star), your weight would be nearly zero, or you would be "weightless." That's why astronauts float around in the space station!
Explore your weight in other worlds, check out the interactive below!
Your weight in other worlds
Click on the image to calculate how much you weigh if you were to stand on different planets, moons or even stars. Remember - your weight changes due to the different gravitational forces pulling on you, but your mass does NOT change. If you go on to read about gravity on that same page, it explains why the neutron star has such tremendous gravitational pull.
STATES OF MATTER
What is Density??
How molecules move in different states of matter
Click on the picture to play "Change It".
Test your knowledge!
What happens when roads expand too much in the heat!
Roads are built with expansion joints or seams which are designed to accommodate when roads expand with the heat and contract in the cold. Sometimes, on long stretches of very hot days, the cement slabs expand so much that the seams can't accommodate the expansion. This causes the slabs to press against each other until they can no longer take the pressure, causing the road to buckle as they did in the image above. See what happens when a Wisconsin driver (see this link) didn't see it and went airborne (but wasn't hurt) after a long, very hot spell of 100 degree + days.
Float or Sink? A Rule for What Floats
Water is wonky!
- Interestly, water is wonky because it is at its most dense at 4 degrees C when it is still a liquid. Therefore, the solid form of water (ice) is actually less dense than its liquid form. That's why ice floats on water instead of sinks.
- Another interesting fact about water is that it is the only substance that exists on the planet in all 3 states of matter.
Think about it. What if rock existed in all 3 states of matter on the surface of our planet? Or the air we breathe?
What does density have to do with Layers of the Earth???
- When the earth was a hot, molten mass early in its formation, the more dense liquid nickel and iron sank (to the core) below the less dense molten rock of the mantle.
- The intense pressure of the layers above the inner core caused the iron and nickel to compact under pressure and become a solid - even though it is hot enough to be melted into a liquid at lower pressures. In fact, if you move outward to the outer core, the temperatures (less heat energy) are lower than those at the inner core, but the iron and nickel are now liquid.
- The oceanic crust is mostly made up of a rock called basalt, which is more dense than the (silicate) granite rock of the continental crust. The uppermost part of the mantle and the crust are together called the lithosphere. "Lith" means rock, which describes the lithosphere - rocky. The less dense lithosphere floats atop the more dense asthenosphere. The oceanic lithosphere, being more dense than the continental lithosphere, sinks lower on the asthenosphere.
You can compare this to the bouncy ball and the styrofoam ball we saw during our class demonstration. The bouncy ball floated much lower in the water than the styrofoam ball. Even though both are less dense than the water and float, one is much less dense (styrofoam) and floats higher. Similarly, that's why the oceanic crust floats lower than the continental crust.