Gas models and absolute temperature
도입됨| English | 의미 |
|---|---|
| absolute temperature/ˈæbsəluːt ˈtemprɪtʃə/ | 절대 온도 |
| ideal gas/aɪˈdɪəl ɡæs/ | 이상 기체 |
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
- Gas particles move randomly and collide with container walls. Pressure depends on collisions with the walls. At fixed temperature, compression reduces volume and increases pressure for a fixed amount of gas.
- absolute temperature: Temperature on the kelvin scale; ideal gas 理想气体: A gas model with specified simplifying assumptions.
For a fixed amount of gas at constant temperature, halving volume does what to pressure?
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At fixed temperature the gas particles keep their average speed, so halving the volume doubles how often they hit the walls - the pressure doubles (pV = constant). Halving the pressure would require the volume to double instead.
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
- State which quantities stay fixed. A pressure-volume relation requires consistent units and a fixed temperature. The kelvin-based temperature ratio is an extension only where the course explicitly specifies it.
- 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: gas pressure is 100 kPa at volume 60 cubic centimetres, at fixed temperature. p1V1=p2V2. At volume 30 cubic centimetres, p2=p1V1/V2=100×60/30=200 kPa.
At fixed temperature, pressure is 120 kPa at volume 50 cubic centimetres. Find pressure at volume 30 cubic centimetres. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
At fixed temperature, pressure is 120 kPa at volume 50 cubic centimetres. Find pressure at volume 30 cubic centimetres.
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The result is 200 kPa. Known: p1 = 120 kPa at V1 = 50 cubic centimetres, fixed temperature and amount; V2 = 30 cubic centimetres. Use p1V1 = p2V2. Rearranging: p2 = p1V1/V2 = 120 x 50/30 = 200 kPa. The smaller volume gives a proportionally higher pressure.
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.
At fixed temperature, halving gas volume halves its pressure. This claim is false: At fixed temperature pressure and volume are INVERSELY linked: pV = constant. Halving the volume doubles the pressure, so pressure moves in the opposite direction to volume, not the same direction.
Gas models and absolute temperature: State which quantities stay fixed. A pressure-volume relation requires consistent units and a fixed temperature. The kelvin-based temperature ratio is an extension only where the course explicitly specifies it.
At fixed temperature, halving gas volume halves its pressure.
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At fixed temperature pressure and volume are INVERSELY linked: pV = constant. Halving the volume doubles the pressure, so pressure moves in the opposite direction to volume, not the same direction.
Temperature on the kelvin scale: write the technical term.
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absolute temperature means Temperature on the kelvin scale.