Let's break down each of the questions:
Question 61: The two sides of the above equation appear different. These differences are evidence of a —
- A mass change
- B physical change
- C chemical change
- D temperature change
In this context, if the two sides of the equation represent the reactants and products of a chemical reaction, then the differences between them would indicate a C) chemical change.
Question 62: Students conduct a lab in which they neutralize an acid. Which of the following is the last thing students should do before leaving the lab area?
- A disassemble the equipment
- B wash their hands
- C record their observations
- D clean the lab tables
The best answer here would be C) record their observations. It is important to document findings as the last step before leaving the lab. However, it's also critical to clean and ensure safety, so B) wash their hands should also be done, but typically you would record observations first.
Question 63: The following reaction occurs in a sealed container. Three grams of hydrogen and 24 grams of oxygen were completely reacted to form water. Which of the following is the amount of water produced?
- A 8 grams
- B 21 grams
- C 27 grams
- D 72 grams
To find the total mass of water produced, according to the law of conservation of mass, you would add the masses of the reactants together.
3 grams of hydrogen + 24 grams of oxygen = 27 grams of water.
So, the correct answer is C) 27 grams.