Gas identification: oxygen relights a glowing splint
| English | Português |
|---|---|
| glowing splint | glowing splint |
| relighting | relighting |
What would explain this observation?
- A splint whose flame has gone out can still glow. If it relights inside the sampled gas, the specified observation supports oxygen.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- The oxygen test uses a glowing splint 带火星木条 inserted into a test tube of gas. The splint relights in oxygen. The splint is glowing before it is inserted, rather than already carrying a flame; this makes relighting 复燃 an observable change. Write glowing splint and relights together in an identification answer. A burning splint giving a pop is the hydrogen test and is not interchangeable with this method.
- glowing splint: A wooden splint with a glowing tip rather than an existing flame; relighting: Resumption of a flame from the glowing splint in the stated oxygen test.
What is the positive oxygen-test observation?
Oxygen supports combustion but is not itself described as a flammable fuel in this test. Increased burning is evidence about combustion conditions; the school identification relies on the characteristic relighting observation. Colourless gas or a known source reaction alone is weaker evidence than a correctly performed test. A sample mixed with air or contaminated during collection may give less clear observations, so retain uncertain results rather than inventing an identification.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Oxygen supports combustion but is not itself described as a flammable fuel in this test. Increased burning is evidence about combustion conditions; the school identification relies on the characteristic relighting observation. Colourless gas or a known source reaction alone is weaker evidence than a correctly performed test. A sample mixed with air or contaminated during collection may give less clear observations, so retain uncertain results rather than inventing an identification.
- For actual supervised testing, the teacher chooses the source, collection method and small sample quantity. Prepare the splint with a clearly glowing tip under the approved method, then place it into the collected gas as instructed. Use eye protection and keep ignition arrangements separate from incompatible flammable substances. Record the starting splint state and whether it relights; do not describe the flame’s colour as the required identifying observation.
Which two habits make the investigation or model in this case more defensible?
For actual supervised testing, the teacher chooses the source, collection method and small sample quantity. Prepare the splint with a clearly glowing tip under the approved method, then place it into the collected gas as instructed. Use eye protection and keep ignition arrangements separate from incompatible flammable substances. Record the starting splint state and whether it relights; do not describe the flame’s colour as the required identifying observation.
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: a fictional comparison table records clear relighting in four of five suitable sample observations. The clear-positive proportion is 4/5×100=80%. This illustrates recording and interpretation, not oxygen concentration. Counting outcomes cannot convert the test into a quantitative purity measurement without an independently calibrated method and appropriate evidence.
A supplied table records six clear relightings in eight observations. Calculate their percentage. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A supplied table records six clear relightings in eight observations. Calculate their percentage.
The result is 75 %. Known: a fictional comparison table records clear relighting in four of five suitable sample observations. The clear-positive proportion is 4/5×100=80%. This illustrates recording and interpretation, not oxygen concentration. Counting outcomes cannot convert the test into a quantitative purity measurement without an independently calibrated method and appropriate evidence.
Check the conclusion and its limits
- A splint already burning cannot demonstrate relighting from a glow. Do not write oxygen burns with a pop, or assume every gas that permits some burning is pure oxygen. The qualitative test gives identification support under suitable conditions and has observation limits. Both tiers need the specified test; performing it in school remains distinct from answering a written gas question.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Oxygen itself is the flammable fuel consumed in the splint test. This claim is false: A splint already burning cannot demonstrate relighting from a glow. Do not write oxygen burns with a pop, or assume every gas that permits some burning is pure oxygen. The qualitative test gives identification support under suitable conditions and has observation limits. Both tiers need the specified test; performing it in school remains distinct from answering a written gas question.
Gas identification: oxygen relights a glowing splint: Oxygen supports combustion but is not itself described as a flammable fuel in this test. Increased burning is evidence about combustion conditions; the school identification relies on the characteristic relighting observation. Colourless gas or a known source reaction alone is weaker evidence than a correctly performed test. A sample mixed with air or contaminated during collection may give less clear observations, so retain uncertain results rather than inventing an identification.
Oxygen itself is the flammable fuel consumed in the splint test.
A splint already burning cannot demonstrate relighting from a glow. Do not write oxygen burns with a pop, or assume every gas that permits some burning is pure oxygen. The qualitative test gives identification support under suitable conditions and has observation limits. Both tiers need the specified test; performing it in school remains distinct from answering a written gas question.
A wooden splint with a glowing tip rather than an existing flame: write the technical term.
glowing splint means A wooden splint with a glowing tip rather than an existing flame.