No mathematics the most common way of solving an equation will be PEMDAS so the answer for your question will most likely be subtraction.
I think thee correct answer from the choices listed above is option D. <span>When a physical change in a sample occurs, composition of the sample does not change. It stays the same. Also, the properties of the sample will still be the same. Hope this answers the question.</span>
Answer: OH−.
Explanation: Hydroxide, any chemical compound containing one or more groups, each comprising one atom each of oxygen and hydrogen bonded together and functioning as the negatively charged ion OH-.
Answer:
B. A chemical change occurred which caused the liquid's physical properties to change.
Explanation:
The reduction of the temperature of the system meant that the reaction absorbed heat energy from it. This shows that a chemical reaction was in progress. New products were formed, and this is proved by the change in the color to blue.
I think the correct answer is option A. Pure substances can be considered as compounds. Compounds are molecules made of atoms from different elements held together by chemical bonds. Pure substances are these compounds that exist alone no other substance.