1) Left up: a chemical change. We can see new substance (red-blue) is formed from one blue and one red atom.
In chemical change new substances are formed, the atoms are rearranged and the reaction is followed by an energy change.
2) Left down: a chemical change. We can see new substance (red-blue) is formed from two blue and one red atoms.
3) MIddle: a physical change. There is no new substance. Bonds are not broken.
4) Right up: a chemical change. Bonds are broken.
5) Right down: a physical change. Change of state of matter.
The particles in a solid are tightly packed and locked in place. Although we cannot see it or feel it, the particles are vibrating in place.
As these molecules heat up, they will vibrate more vigorously, and will eventually turn to water, then gas.
Answer:
A. True
Explanation:
The octane number is determined by comparing the characteristics of gasoline to isooctane (2,2,4-trimethylpentane) and heptane. The correct option is option A.
Basically, the higher the octane number, the greater the resistance of the gasoline to knocking.
Answer:
Percent yield = 21%
Explanation:
Find:
Percent yield
Computation:
1 mol O₂ produces 2 mol NO₂
So,
10 mol O₂ produces 20 mol NO₂
Percent yield = [Actual yield / Theoretical yield]100
Percent yield = [4.2 / 20]100
Percent yield = 21%
20 minutes.
The sample would lose one half the quantity of francium in each half-life.
Thus a mass decrease by a factor of 16 would correspond to a period of four half-lives. It took 80 minutes for the sample to lose all these francium, therefore
minutes.
