A physical change<span> in a substance doesn't </span>change<span> what the substance is. In a </span>chemical change<span> where there is a </span>chemical reaction<span>, a new substance is formed and energy is either given off or absorbed.</span>
B. Copper since the rest of the choices are compounds. Copper is an element.
A the collisions between water particles and polllen grains
The quantity which is equivalent to the product of the absolute index of refraction of water and the speed of light in water system is the speed of light in vacuum.
<h3>What is the speed of light?</h3>
Speed of light is the rate of speed though the light travels. To find the speed of light in any medium, the following formula is used.

Here, (n) is the index of reaction and (c) is the speed of light in the vacuum. The speed of light in the vacuum is almost equal to the 3.0×10⁸ m/s.
Now the quantity which is equivalent to the product of the absolute index of refraction of water and the speed of light in water has to be find out.
The above formula can be written as,

Here, the product of index of refraction and speed of light is equal to the speed of light in vacuum. This will be true for water as well.
Thus, the quantity which is equivalent to the product of the absolute index of refraction of water and the speed of light in water system is the speed of light in vacuum.
Learn more about the speed of light here;
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<span>Answer:
mol Al2O3 x 1 mol Al/ 2 mol Al2O3= .25 mol Al
The balanced equation tells us that it takes 4 moles of Al to produce 2 moles of Al2O3.
0.50 moles Al2O3 x (4 moles Al / 2 moles Al2O3) = 1.0 moles Al
1.0 moles Al x (27.0 g Al / 1 mole Al) = 27.0 g Al</span>