KBr i guess, because the + and - charge is 1 so its like that
Because people make those substance out of other things
Explanation:
a) The amount of heat released by coffee will be absorbed by aluminium spoon.
Thus, 
To calculate the amount of heat released or absorbed, we use the equation:

Also,
..........(1)
where,
q = heat absorbed or released
= mass of aluminium = 45 g
= mass of coffee = 180 g
= final temperature = ?
= temperature of aluminium = 
= temperature of coffee = 
= specific heat of aluminium = 
= specific heat of coffee= 
Putting all the values in equation 1, we get:
![45 g\times 0.80J/g^oC\times (T_{final}-24^oC)=-[180 g\times 4.186J/g^oC\times (T_{final}-83^oC)]](https://tex.z-dn.net/?f=45%20g%5Ctimes%200.80J%2Fg%5EoC%5Ctimes%20%28T_%7Bfinal%7D-24%5EoC%29%3D-%5B180%20g%5Ctimes%204.186J%2Fg%5EoC%5Ctimes%20%28T_%7Bfinal%7D-83%5EoC%29%5D)

80.30 °C is the final temperature.
b) Energy flows from higher temperature to lower temperature.Whenever two bodies with different energies and temperature come in contact. And the resulting temperature of both bodies will less then the body with high temperature and will be more then the body with lower temperature.
So, is our final temperature of both aluminium and coffee that is 80°C less than initial temperature of coffee and more than the initial temperature of the aluminum.
The air molecules in the compressions of the second wave are denser, so the sound is louder.
<h3>What is a sound wave?</h3>
Sound waves are longitudinal waves that travel through a medium like air or water.
In a closed room, Noah and Nina are sitting 15 m apart.
As Noah says the same sentence twice, Nina does not hear the sound the first time but she does hear the sentence the second time.
This happens as the air molecules in the compressions of the second wave are denser. As a result, the sound is louder.
The correct option is ''The air molecules in the compressions of the second wave are denser, so the sound is louder''.
Learn more about the sound wave here:
brainly.com/question/1554319
#SPJ1