The correct answer is:Some substances keep the same molecular structure when they break down, and others do not.
Some substances change their form when they dissolve and some do not. Dissolution can sometimes be regarded as a sort of reaction between a chemical substance and water.
Usually, we can consider dissolution of a substance in water as a sort of chemical reaction for some substances. For instance, an ionic substance interacts with water to form ions. similarly, some salts become hydrolysed in water and give acidic/basic solutions as result of that.
However, some substances do not interact with water upon dissolution. They rather remain as molecular entities because they are not composed of ions.
We can see that some substances keep the same molecular structure when they break down, and others do not keep the same molecular structure when they dissolve hence it is difficult to classify dissolving as a physical or a chemical change.
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Answer:
There are significant environmental impacts associated with coal mining and use. It could require the removal of massive amounts of top soil, leading to erosion, loss of habitat and pollution. Coal mining causes acid mine drainage, which causes heavy metals to dissolve and seep into ground and surface water.
Explanation:
Answer:
The tension in the string is 78.73 N.
Explanation:
The tension in the string can be determined from the expression;
v = 
where: v is the speed of the wave in the sting, T is the tension in the string and m is the mass per unit length of the sting.
Given that: v = 16.2 m/s, and m = 0.3 kg/m.
Then;
16.2 = 
Square both sides to have,
= 
T = x 0.3
= 252.44 x 0.3
= 78.732
T = 78.732 N
The tension in the string is 78.73 N.
<span>The number of moles of Cl- ions needed to combine completely with 0.25 mole of Mg+2 ions is:
0.50.</span>
