THSB
Substances, Chemical Reactions, and Conservation of Matter
Item SC069007: When a chemical reaction occurs, the characteristic properties of the products are different than the characteristic properties of the reactants. (This item used a table to show the properties of the substances.)
A student determines the density, solubility, and boiling point of two liquids, Liquid 1 and Liquid 2. Then he stirs the two liquids together and heats them. After stirring and heating the liquids, two different liquids form, Liquid 3 and Liquid 4. Then the student determines the density, solubility, and boiling point of Liquids 3 and 4. He concludes that a chemical reaction occurred. Here are his results:
| Density (g/mL) | Soluble in Water | Boiling Point (°C) | ||
| Before stirring and heating | Liquid 1 | 0.96 | Yes | 164 |
| Liquid 2 | 0.81 | Yes | 118 | |
| After stirring and heating | Liquid 3 | 0.87 | Yes | 166 |
| Liquid 4 | 1.00 | Yes | 100 | |
How does the student know that a chemical reaction has occurred?
- The student knows that a chemical reaction has occurred because
Liquid 3 has different properties than Liquid 4. - The student knows that a chemical reaction has occurred because
Liquid 1 has different properties than Liquid 2. - The student knows that a chemical reaction has occurred because
Liquids 3 and 4 have different properties than Liquids 1 and 2. - The student knows that a chemical reaction has occurred because
a chemical reaction always occurs when two liquids are mixed together.
(Modified from IQWST)
- Distribution of Responses
- Points Earned
| Group | Correct | Total | Percent |
|---|---|---|---|
| Overall | 260 | 362 | 72% |
| Grades | |||
| 6–8 | 260 | 362 | 72% |
| 9–12 | N/A | N/A | N/A |
| Gender | |||
| Male | 144 | 201 | 72% |
| Female | 116 | 161 | 72% |
| Primary Language | |||
| English | 245 | 335 | 73% |
| Other | 15 | 27 | 56% |
- Distribution of Responses
- Points Earned
| Group | Correct | Total | Percent |
|---|---|---|---|
| Overall | 288 | 361 | 80% |
| Grades | |||
| 6–8 | 288 | 361 | 80% |
| 9–12 | N/A | N/A | N/A |
| Gender | |||
| Male | 152 | 197 | 77% |
| Female | 136 | 164 | 83% |
| Primary Language | |||
| English | 271 | 333 | 81% |
| Other | 17 | 28 | 61% |
- Disciplinary Core Ideas
- PS1.A Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it.
- NRC Framework
- Patterns: …objects can be classified into groups on the basis of similarities of visible or microscopic features or on the basis of similarities of function… (4, 85)