Mellen,+Tierney

The article "Motion Detectors" explained how and what different motion detectors detected. Three things I knew before I read this article are that our eyes are sensors in the way they register light waves, that some sensors used a light source to detect things, and that the photoelectric effect is based on the light's frequency, not intensity. One thing I didn't know was that infrared was used with some sensors. I hadn't realized that sensors for catching burglars would need to ignore things like tree branches. Another thing I learned was that snakes had infrared sensors to catch prey in the dark. A third thing I learned is that an automatic door would use signals bouncing off objects. I would have thought it would use something like a beam of light, but I suppose it would be more difficult to make the door open automatically from both sides with that.

Tierney, Good job! I like your summary. Good comment on the tree branches. How annoying would that be? 5 stars. MW

Something I didn't know before watching this video is that crude oil can't be used in its undistilled state. I kinda knew there was such thing as crude oil and that gasoline was made from it, but I didn't know it had to be distilled to be of any use. I also didn't know that more complicated molecules had higher boiling points. Something interesting I found out is that some hydrocarbons boiled at 40 degrees C, less than half of what it takes water to boil. It may be that I'm more used to Fahrenheit, but it seems like a low boiling temperature.

Tierney, It is a pretty low boiling temperature. Human body temperature is 37oC. Good post. 5 stars. MW

I read the article called "Flaking Away" which explains why cars rust. Three things i knew before I read this article are that iron rusts, water helps iron rust, and cars rust. One thing I learned is that salt helps iron rust faster by helping the water be a better conductor. I also learned that rust is made with an anode, which releases electrons, a cathode, which accepts the electrons, and an electrolyte solution, which allows the electrons to move from anode to cathode. Another thing I learned is that cars wouldn't rust if they're made of a metal that doesn't corrode.

Tierney, Good post but you actually read an AP Chemistry article! 5 stars. MW Haha, oops ^^