The answer is "A. a pure substance can be separated by chemical means, while a mixture can be separated by physical means". A pure substance only has one type of substance, whereas a mixture has more than one. A pure substance therefore, can only be separated chemically, because it is not two things mixed together, whereas a mixture can be separated physically because there are multiple substances.
One type of chemical process that can be either exothermic or endothermic is dissolving of salts in water. A salt is a compound made up of positively charged ions and negatively charged ions which are held together in a solid state because the positive and negative charges attract one another.
Energy = Planck's constant * Frequency
E = (6.62607004 × 10⁻³⁴<span>) * 7 * 10</span>¹⁴
E = 46.38 * 10⁻²⁰
E = 4.638 * 10⁻¹⁹ J
Hope this helps!
D is the answer cause two h20 + o2(g)
