ASPECt
Energy: Forms, Transformation, Transfer, and Conservation
Temperature variations in fluids such as air and water lead to currents that circulate the fluid, and this circu…
Item RG008003: When a cup of water is heated over a flame, the thermal energy of the water at the bottom increases and the heated water will rise to the top of the cup. The cooler water at the top of the cup will sink to the bottom where its thermal energy will be increased by the flame.
A student fills a cup with room temperature water. Then she places the cup over a flame to heat the water.
What will happen to the thermal energy of the water in the cup?
- The thermal energy of the water at the bottom of the cup will increase as the cup of water is heated. The heated water will rise to the top of the cup, and the cooler water at the top of the cup will sink to the bottom where its thermal energy will be increased by the flame.
- The thermal energy of the water at the bottom of the cup will gradually spread from the bottom to the top of the cup until all the water has the same thermal energy. Warmer water at the bottom of the cup will not rise to the top, and cooler water at the top of the cup will not sink to the bottom.
- Heat molecules will form at the bottom of the cup and spread throughout the water as the water is heated. The thermal energy of the water will increase as the number of heat molecules increases.
- While the water is over the flame, the thermal energy of all parts of the water will increase at the same time.
- Distribution of Responses
- Scale Score for Item Difficulty
(200[Easy]-800[Difficult]) - 495
- Students Responding Correctly
| Group | Correct | Total | Percent |
|---|---|---|---|
| Overall | 1695 | 3796 | 45% |
| Grades | |||
| 4–5 | 183 | 481 | 38% |
| 6–8 | 766 | 1673 | 46% |
| 9–12 | 746 | 1642 | 45% |
| Gender | |||
| Male | 801 | 1724 | 46% |
| Female | 842 | 1960 | 43% |
| Primary Language | |||
| English | 1539 | 3421 | 45% |
| Other | 104 | 248 | 42% |
- Disciplinary Core Ideas
- PS3.B Energy is spontaneously transferred out of hotter regions or objects and into colder ones.
- NRC Framework
- Heating is another process for transferring energy. Heat transfer occurs when two objects or systems are at different temperatures. Energy moves out of higher temperature objects and into lower temperature ones, cooling the former and heating the latter. This transfer happens in three different ways—by conduction within solids, by the flow of liquid or gas (convection), and by radiation, which can travel across space.