Structure of Matter Study Materials
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Structure of Matter Study Guide
Almost all things are made of matter (excluding things like light and gravity). Matter is made of atoms which combine to form molecules. Atoms are in perpetual motion and the more energy they have the faster they move. We can measure matter's mass, volume, and density. Density is a measure of the compactness of matter and determines the way materials in a mixture sort.
Describe the structure of matterEverything is made of tiny pieces called atoms. Atoms are so tiny that we can't even see them with our most powerful microscopes. But we're getting close! Our most powerful microscopes allow us to see two large atoms stuck together. There are many different types of atoms and we call those elements.
Elements (the kinds of atoms) combine to form molecules. Molecules can be big (hundreds of atoms stuck together) or small (just two atoms stuck together). Everything is made of molecules. There are three main states of matter: solid, liquid, and gas. Examples of solids include a table, a pencil, and ice. The atoms in a solid are packed tightly together (often in a particular order and pattern) and slowly vibrate. Atoms in a liquid are packed less tightly together and flow around each other. Atoms in a gas are often very spread out and speed around each other. Since we can't see atoms, we use models to describe what they look like. We use math and deductive reasoning to figure out what they look like since we can't see them. But models always have limitations (things they just can't show very well). Two common limitations of atom models are the fact that they can't show all the empty space and they can't show the electron movement.
Our model has taken 100's of years to make. Scientists like Bohr, Rutherford, Thompson, and others built on each other's work, fixing old models and adding new details they found using math and experiments. |
Measure characteristics of matterAll matter has three characteristics: mass, volume, and density. Mass tells us how many atoms are in the object (how much matter is there). Volume tells us how big the object is (how much space does it take up). And density describes how packed that atoms in the object are.
We use a triple beam balance or scale to find the mass of an object. For anything with a regular shape (like a box), we can calculate the density using a ruler and equations. For weird shaped objects we use the technique called water displacement and a tool called a graduated cylinder. To do the technique called water displacement, you put some water in a graduated cylinder, note the volume of the water, add the object, and note the new volume. The volume of the object you added is simply the final volume minus the original water volume. Without calculating density, we can predict something's relative density just by observing whether something floats or sinks. Anything with a smaller number for density (anything that is less dense) will float and anything with a larger number for density (anything that is more dense) will sink. For instance, the density of water is 1 g/ml. So if something floats in water, you can accurately predict that its density is less than 1 g/ml. In order to calculate density, you simply divide the object's mass by its volume. The units for density are either g/mL or g/cm^3. If you truly understand the density equation, you'll realize that if the mass is greater than the volume, the density will be small and thus the item will float in water. And the opposite is true as well. If the volume is greater than the mass, the density will be larger and the item will sink in water. Thus, if mass stays the same, but volume increases the density will decrease. If the mass increases but the volume stays the same, the density will increase. |
Investigate motion of matterAtoms are constantly moving. Not just because they make up moving things. They also move entirely on their own. Because atoms are so small, you may think that this is hard to observe. But if you smell something, that is because the atoms that make up that smell have moved into your nose. That is why smells spread. The atoms are moving all on their own. You can also observe this if you put food coloring in water or observe the change of volume in a hot solid.
When temperature increases (when things get hotter), the atoms get more energy and move faster. Because they are moving faster, they bump into each other more and spread out, causing their volume to increase. When temperature decreases (when things get colder), the atoms lose energy and move slower. Because they are moving slower, they don't bump into each other as much and will slowly move closer together, causing their volume to decrease. Diffusion is the word we use for when atoms spread away from each other. This can happen in any state of matter, but is the easiest to see in liquids and gasses. For instance, food coloring will fill the container faster (as the food coloring atoms spread away from each other) in hot water. When something's volume increases, we say that the atoms have expanded. When something's volume decreases, we say that the atoms have contracted. This movement of atoms needs to be accounted for in construction. For instance, we know that concrete expands in the summer (because it is hotter, the atoms move faster, and spread out). To keep the concrete from cracking when it tries to get bigger in a confined space, we put pre-made sidewalk cracks (spaces) to allow the sidewalk to expand. We leave this kind of extra space in bridges, windows, and other construction projects. |
Vocabulary
Atoms:
the tiny pieces that make up all matter Molecules: any combination of atoms State of Matter: the forms matter takes Solid: the tightly packed and slow moving state Liquid: the state of matter that is less packed and flows around Gas: the state of matter that is very spread out and has fast moving atoms Model: a representation of something that is too big, too small, or too complicated to understand normally Limitation: something a model cannot easily show |
Mass:
a measure of how much matter is in an object Volume: a measure of the space an object takes up Density: describes the compactness of the atoms in an object Triple Beam Balance: a tool used to find mass Scale: a tool used to find weight (which is the same as the mass on earth) Graduated Cylinder: a tool (tube like) used to find the volume of weird objects and liquids Ruler: a stick with measurements of length on it |
Increases:
gets bigger in number or amount Decreases: gets smaller in number or amount Diffusion: atoms spread away from each other Contract: volume decreasing as atoms get closer Expand: volume increasing as atoms spread out |