So far, we've learned a lot about mass, volume, density, and measuring them. To measure mass, we used grams, for volume we used mL or cubic centimeters, and for density we used grams per mL, or mass per unit of volume. Knowing this information is important for measuring objects, especially knowing mass, because all matter has mass.
We've covered a lot about mass and change, and learned about what happens to the mass of a substance when you dissolve it (the mass is unchanged), or when you burn it (the mass increases in size).
We've also learned about significant and estimated digits in a number. We've also learned about significant zeros and their five rules:
1. All non-zero numbers are significant. For example, all the digits in 155 are significant.
2. Sandwiched zeros are significant. For example, the zero in 101 is significant.
3. Zeros that are only placeholders for a decimal aren't significant. For example, the zeroes in 200 aren't significant.
4. Zeros at the end of a number that also contains a decimal are significant. For example, the zeros at the end of 0.400 are significant.
5. Exact numbers have an infinite number of significant zeros. For example, if there are 13 people in a room, then that number, 13, has an infinite number of significant zeroes.
It's important that we know when zeros and digits are significant and when to use an estimated digit for measuring objects. For example, when measuring the side of a piece of wood with a ruler that only has dashes for inches, you'll have to record how many inches the side is, and then add one estimated digit which is more specific than the inch, in order for the information to be correct.
We had a unit exam on Tuesday covering all of what we learned, and then we started on a new concept: particle movement. We only covered this concept on Thursday and Friday, but we were able to fit in two experiments.
For one experiment, Dr. Finnan stood in the corner of the room and opened a bag of popcorn. He asked us to raise our hands when we smelled the popcorn odor. The tables closest to him raised their hands first and that hand raising steadily spread to the tables in the back. This proves that particles move because the popcorn odor particles got all the way from one side of the room to the other.
The next experiment we did included two beakers of water, one hot and one cold. We dropped one drop of blue food coloring into each and then watched its movement. This is a video of the event:
As you can see, in the hot water, the coloring spread much quicker than in the cold water. Our table concluded that the energy from the hot water allowed for the particles in the food coloring to move more fluidly throughout the water, while the lack of thermal energy in the cold water caused the particles to move more slowly. From this experiment, we learned that heat energy exists.
We also watched some videos explaining molecule movement in solids and liquids. In solids, molecules don't move too far away from each other, while in liquids they move very far and the attraction between two molecules isn't as strong. The molecules bounce all around inside the substance.
Particle movement and energy connect because particles have energy. Every moving thing has energy. An important detail to particle movement is that it moves differently depending on what state of matter an object is in. Particles move quicker and further in liquid and gaseous forms, and less so in solids. When affected by heat energy, particles move quicker. My participation this week was pretty good, and I learned a lot about the material we're being taught. I don't have many questions about what we learned this week, but I would like to learn more about heat energy and how it works.
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