Answer:
Temperature is a common type of controlled variable. If a temperature is held constant during an experiment, it is controlled. Other examples of controlled variables could be an amount of light, using the same type of glassware, constant humidity, or duration of an experiment.
Explanation:
The answer is C, i just took the k-12 test~
Answer: When coal is burned, chemical potential energy is transformed into thermal energy, light energy, and sound energy. Only the thermal energy is used for electricity production. Light and sound energy dissipate into the environment, immediately reducing efficiency.
Hope this helps.
To calculate how many photons are in a certain amount of energy (joules) we need to know how much energy is in one photon.
Start by using two equations:
Energy of a photon = Frequency * Planck's constant (6.626 * 10^(-34) J-s)
Speed of light (constant 3 * 10^8 m/s) = Frequency * Wavelength
Which means:
frequency = Speed of Light / Wavelength
So energy of a photon = (Speed of light * Planck's constant)/(Wavelength)
You may have seen this equation as E = hc/<span>λ</span>
We have a wavelength of 691 nm or 691 * 10^-9 meters
So we can plug in all of our knowns:
E = (6.626 * 10^(-34) J-s) * (3.00 * 10^8 m/s) / (691 * 10^-9 m) =
2.88 * 10^(-19) joules per photon
Now we have joules per photon, and the total number of joules (0.862 joules)
,so divide joules by joules per photon, and we have the number of photons:
0.862 J/ (2.88 * 10^(-19) J/photon) = 3.00 * 10^18 photons.
Acids react with calcium carbonate and more specifically carbonate to form carbon dioxide. An acid will give protons to the carbonate anion to produce carbonic acid which then decomposes into carbon dioxide and water. I hope this helps. Let me know if anything is unclear.
