Question 1 4 out of 4 points Which of the following is an example of a physical change? Selected Answer: changing from a solid to a liquid Answers: changing from a solid to a liquid changing from colorless to pink releasing light releasing gas bubbles none of the above Response Feedback: In a physical change, the chemical composition of the sample does not change (it keeps its identity). You can ask this question- “Is it still the same substance?” If the answer is yes, it is a physical change. For example, you have chuck of salt. You grind chuck of salt into fine powder. Is this still salt? Yes it is. When ice melts into water, is it still water? Yes it is. When you dissolve sugar is water, sugar disappears but when you drink the water, you can still taste sugar. These are examples of physical change. In a chemical change, a chemical reaction has occurred and new substances are produced. You can ask this question- “Is it still the same substance?” If the answer is no, it is a chemical change. For example, when you burn a piece of paper, is it still paper? No, it is not- it turns to ashes. You can also observe the chemical changes. The common observations are bubbling (or fizzing), heat (light energy), color change, and insoluble solid is formed. Question 2 0 out of 4 points Which of the following elements is an example of a semimetal? Selected Answer: Am Answers: Ar
Ac Al Am As Response Feedback: Semimetals are B, Si, Ge, As, Sb, Te, Po, At. Question 3 4 out of 4 points A rectangular block of copper has a mass of 143.584 g and measures 5.05 cm by 2.55 cm by 1.25 cm. Find the density of the copper block. Selected Answer: 8.92 g/cm 3 Answers: 8.92 g/cm 3 29.0 g/cm 3 11.1 g/cm 3 28.4 g/cm 3 0.112 g/cm 3 Response Feedback: d = m V d = 143.584 g (5.05 cm x 2.55 cm x 1.25 cm) (Note: I did not calculate the volume separate so I can keep track of sig fig, and the smallest is 3 s.f) d = 8.92 g/cm 3 Question 4 4 out of 4 points The addictive drug morphine, C 17 H 19 NO 3 , is used for the treatment of pain. What is the total number of atoms in the chemical formula?
Selected Answer: 40 Answers: 40 4 42 39 none of the above Response Feedback: C 17 H 19 NO 3 = 17+19+1+3 = 40 Question 5 0 out of 4 points If a penny has a mass of 3.015 g and is 5.00% zinc, what is the mass of zinc in the coin? Selected Answer: 1.51 g Answers: 1.51 g 0.151 g 2.86 g 0.286 g 0.603 g Response Feedback: The formula for finding percent is % of interest = amount of interest x 100 % total amount Reading the question, the percent of Zn is given as 5.00 %, and the mass of penny (total amount) is 3.015 g. It is asking for mass of Zn, I need to solve for the amount of interest (Zn). Plug this information to formula above. 5.00 % Zn = __X g __ x 100% 3.015 g
Solve for X. X = 0.15075 g Zn --> Round it to 3 significant figures --> 0.151g Zn Question 6 4 out of 4 points Which of the following requires a chemical method to be separated into two or more pure substances?
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