Item SB002002: During a reaction where a reactant enters the system and no products leave, the mass of the system increases because the system now contains more atoms.
A scientist is investigating changes in mass that may occur during chemical reactions. First, she pours a colorless liquid into a test tube and measures the mass of the liquid. Then she puts a straw in her mouth and blows air into the liquid through the straw. A chemical reaction occurs and a white solid forms in the liquid, which makes the liquid look cloudy. No gas is produced. The scientist measures the mass of the cloudy liquid and compares it to the mass of the liquid before she blew air into it.
Will the mass of the cloudy liquid be more than or the same as the mass of the liquid before the scientist blew air into it? Why?
The mass of the cloudy liquid will be more than the mass of the liquid before the scientist blew into it…
A. because new atoms are created in the test tube when the scientist blows into the liquid.
B. because molecules from the scientist's breath reacted with molecules in the liquid to form a solid substance that stayed in the test tube, so the number of atoms in the test tube increased.
The mass of the cloudy liquid will be the same as the mass of the liquid before the scientist blew into it…
C. because the molecules from the scientist's breath passed through the liquid and left the test tube, so the number of atoms in the test tube does not change.
D. because the scientist's breath does not have mass and does not add atoms to the test tube.
Pre-Test
Answer Choice |
Overall |
Grades |
Gender |
Primary Language |
|||
|---|---|---|---|---|---|---|---|
| n = 356 |
6–8 n = 356 |
9–12 n = 0 |
Male n = 194 |
Female n = 162 |
English n = 330 |
Other n = 26 |
|
| A. | 17% | 17% | NAN% | 16% | 17% | 16% | 23% |
| B. | 46% | 46% | NAN% | 44% | 48% | 47% | 31% |
| C. | 25% | 25% | NAN% | 26% | 25% | 25% | 31% |
| D. | 13% | 13% | NAN% | 14% | 11% | 12% | 15% |
Post-Test
Answer Choice |
Overall |
Grades |
Gender |
Primary Language |
|||
|---|---|---|---|---|---|---|---|
| n = 347 |
6–8 n = 347 |
9–12 n = 0 |
Male n = 186 |
Female n = 161 |
English n = 320 |
Other n = 27 |
|
| A. | 12% | 12% | NAN% | 11% | 12% | 11% | 19% |
| B. | 63% | 63% | NAN% | 65% | 60% | 64% | 44% |
| C. | 20% | 20% | NAN% | 19% | 22% | 20% | 22% |
| D. | 5% | 5% | NAN% | 5% | 6% | 5% | 15% |