Crude oil: a finite mixture, not one compound
導入済み| English | 意味 |
|---|---|
| crude oil/kruːd ɔɪl/ | 原油 |
| hydrocarbon/ˈhaɪdrəkɑːbən/ | 炭化水素 |
What would explain this observation?
- A refinery receives crude oil 原油 containing many compounds. It cannot assign the whole liquid one molecular formula, because a mixture has no single fixed chemical composition.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Crude oil is a finite resource found in rocks. It formed from ancient biomass, mainly plankton buried in mud, over geological time. Its rate of formation is far too slow to replace present consumption on a human timescale. Crude oil contains a very large number of compounds; most are hydrocarbons 碳氢化合物. A hydrocarbon molecule contains only hydrogen and carbon atoms. Most hydrocarbons in crude oil belong to the alkane family.
- crude oil: A finite mixture of many compounds, mainly hydrocarbons, formed from ancient biomass; hydrocarbon: A compound containing carbon and hydrogen only.
Which formula represents a hydrocarbon?
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
A hydrocarbon contains hydrogen and carbon ONLY: C4H10 qualifies. C2H5OH contains oxygen (an alcohol), and CO2 has no hydrogen at all.
Match each technical term to its precise meaning.
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- A mixture contains different substances together without a fixed bonding ratio between those substances. Each individual compound still has its own definite formula. C₃H₈ is a hydrocarbon; C₂H₅OH contains oxygen and therefore is not a hydrocarbon, even though it contains carbon and hydrogen. Carbon dioxide is not a hydrocarbon either. Finite describes a limited resource, not a prediction that every deposit will disappear on one exact date.
- Read every element symbol before classifying a formula. Then distinguish statements about an individual molecule from statements about the whole mixture. Use supplied refinery composition data to discuss which components are present and their proportions. A classroom model can use labelled molecular cards; it does not require obtaining or heating crude oil. Keep origin, composition and use as separate parts of an explanation.
Which two habits make the investigation or model in this case more defensible?
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
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: an original sample model contains 20 C₃H₈ molecules, 10 C₂H₆ molecules and 5 oxygen-containing molecules. There are 35 molecules represented, of which 30 are hydrocarbons. Hydrocarbon number percentage = 30/35×100 = 85.7% to one decimal place. This is a count percentage, not a mass percentage or a measured composition of all crude oils.
A model has 24 hydrocarbon molecules among 40 molecules in all. Find the hydrocarbon number percentage. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A model has 24 hydrocarbon molecules among 40 molecules in all. Find the hydrocarbon number percentage.
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
The result is 60 %. Known: 24 hydrocarbon molecules among 40 molecules. Use percentage = hydrocarbons / total x 100. Percentage = 24/40 x 100 = 60%. This is a molecule count, not a mass share.
Check the conclusion and its limits
- Do not call crude oil pure, renewable on a human timescale, or a single alkane. Biomass origin does not make every biomass-derived fuel a fossil fuel. A substance containing carbon is not automatically a hydrocarbon: all of its elements must satisfy the definition. Models and percentages describe only the supplied sample.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Every compound containing carbon is a hydrocarbon. This claim is false: A hydrocarbon must contain carbon AND hydrogen and nothing else. Ethanol, carbon dioxide, glucose and chloroform all contain carbon - none is a hydrocarbon.
Crude oil: a finite mixture, not one compound: A mixture contains different substances together without a fixed bonding ratio between those substances. Each individual compound still has its own definite formula. C₃H₈ is a hydrocarbon; C₂H₅OH contains oxygen and therefore is not a hydrocarbon, even though it contains carbon and hydrogen. Carbon dioxide is not a hydrocarbon either. Finite describes a limited resource, not a prediction that every deposit will disappear on one exact date.
Every compound containing carbon is a hydrocarbon.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
A hydrocarbon must contain carbon AND hydrogen and nothing else. Ethanol, carbon dioxide, glucose and chloroform all contain carbon - none is a hydrocarbon.
A finite mixture of many compounds, mainly hydrocarbons, formed from ancient biomass: write the technical term.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
crude oil means A finite mixture of many compounds, mainly hydrocarbons, formed from ancient biomass.