Gas models and absolute temperature
Введено| English | Значение |
|---|---|
| absolute temperature/ˈæbsəluːt ˈtemprɪtʃə/ | абсолютная температура |
| ideal gas/aɪˈdɪəl ɡæs/ | идеальный газ |
What would explain this observation?
- A sealed gas container changes pressure when heated. Celsius ratios cannot predict the pressure change because the gas model uses absolute temperature 绝对温度.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- In a gas model, particles move randomly and pressure results from momentum transfer at walls. The ideal gas 理想气体 equation connects pressure, volume, amount and absolute temperature.
- absolute temperature: Temperature on the kelvin scale; ideal gas: A gas model with specified simplifying assumptions.
Which scale belongs in a gas-law temperature ratio?
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Gas-law ratios rest on absolute temperature measured from absolute zero, so kelvin is required. Celsius shifts the zero by 273.15 and breaks every ratio, even though a temperature DIFFERENCE is the same size in both scales.
Match each technical term to its precise meaning.
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Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- At fixed amount and volume, pressure is proportional to kelvin temperature. At fixed temperature and amount, pressure is inversely proportional to volume. State which quantities are fixed before choosing a relationship.
- Use approved apparatus with a temperature range and pressure limit set by the teacher. Allow thermal equilibrium and record pressure against kelvin temperature. Never heat an improvised sealed vessel.
Which two habits make the investigation or model in this case more defensible?
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Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: pressure is 100 kPa at 300 K, with fixed volume and amount. At 330 K, p2/p1=T2/T1. p2=p1 T2/T1=100×330/300=110 kPa. A 30 °C rise is a 30 K change, but the temperature ratio must use kelvin.
At fixed volume, pressure is 120 kPa at 300 K. Find pressure at 350 K. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
At fixed volume, pressure is 120 kPa at 300 K. Find pressure at 350 K.
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The result is 140 kPa. Known: p1 = 120 kPa at T1 = 300 K, fixed volume and amount; T2 = 350 K. Use p2/p1 = T2/T1. Rearranging: p2 = p1 x T2/T1 = 120 x 350/300 = 140 kPa. The ratio works only because both temperatures are in kelvin.
Check the conclusion and its limits
- An ideal gas is a model with conditions of validity. Celsius zero is not zero molecular motion, and internal energy is not determined by pressure alone.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
A gas pressure ratio can always use Celsius temperatures. This claim is false: Ratios of temperatures are meaningful only from absolute zero. 300 K to 350 K is a ratio of 350/300; the same temperatures in Celsius, 27 and 77, give 77/27 - a different, wrong answer.
Gas models and absolute temperature: At fixed amount and volume, pressure is proportional to kelvin temperature. At fixed temperature and amount, pressure is inversely proportional to volume. State which quantities are fixed before choosing a relationship.
A gas pressure ratio can always use Celsius temperatures.
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Ratios of temperatures are meaningful only from absolute zero. 300 K to 350 K is a ratio of 350/300; the same temperatures in Celsius, 27 and 77, give 77/27 - a different, wrong answer.
Temperature on the kelvin scale: write the technical term.
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absolute temperature means Temperature on the kelvin scale.