Higher Tier: moles connect mass to stated particles
| English | Français |
|---|---|
| mole/məʊl/ | molaire |
| Avogadro constant/ˌævəˈɡædrəʊ ˈkɒnstənt/ | constante d'Avogadro |
What would explain this observation?
- Higher Tier: One mole 摩尔 of carbon atoms and one mole of carbon dioxide molecules contain the same number of stated particles, although their masses and atom contents differ.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Chemical amount is measured in moles, symbol mol. One mole contains 6.02×10²³ of the stated particles, the GCSE value of the Avogadro constant 阿伏伽德罗常数. For a substance with relative formula mass Mr, one mole has mass numerically Mr grams; its molar mass has unit $\dfrac{\text{g}}{\text{mol}}$. Calculate amount n=mass in grams divided by molar mass. For 11 g CO₂ with Mr=44, n=11/44=0.25 mol.
- mole: The unit of amount containing 6.02×10²³ stated particles at the GCSE approximation; Avogadro constant: The number of stated particles per mole, here 6.02×10²³ per mol.
What is equal in one mole of C atoms and one mole of CO₂ molecules?
State what is being counted. A mole of CO₂ molecules contains one mole of carbon atoms and two moles of oxygen atoms, three moles of atoms altogether. A mole of NaCl formula units corresponds to one mole of Na⁺ ions and one mole of Cl⁻ ions in the ionic lattice. Calling either sample simply a mole of particles without specifying which particles can make an answer ambiguous.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- State what is being counted. A mole of CO₂ molecules contains one mole of carbon atoms and two moles of oxygen atoms, three moles of atoms altogether. A mole of NaCl formula units corresponds to one mole of Na⁺ ions and one mole of Cl⁻ ions in the ionic lattice. Calling either sample simply a mole of particles without specifying which particles can make an answer ambiguous.
- Write mass, molar mass and amount in separate columns. Convert kilograms or milligrams into grams before dividing. Rearrange n=m/M to m=nM or M=m/n as needed. Calculate particle number as n×6.02×10²³ and retain standard form; divide particle number by the same constant to find amount. Use sensible significant figures and keep relative mass distinct from molar-mass units.
Which two habits make the investigation or model in this case more defensible?
Write mass, molar mass and amount in separate columns. Convert kilograms or milligrams into grams before dividing. Rearrange n=m/M to m=nM or M=m/n as needed. Calculate particle number as n×6.02×10²³ and retain standard form; divide particle number by the same constant to find amount. Use sensible significant figures and keep relative mass distinct from molar-mass units.
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: 0.50 mol water has mass 0.50×18=9.0 g and contains 3.01×10²³ water molecules. Each molecule has two H atoms, so the hydrogen-atom count is 6.02×10²³. The three atoms per molecule do not change the number of water molecules in the sample.
Calculate the amount in 22 g CO₂ using molar mass 44 $\dfrac{\text{g}}{\text{mol}}$. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Calculate the amount in 22 g CO₂ using molar mass 44 g per mol.
The result is 0.5 mol. Known: 0.50 mol water has mass 0.50×18=9.0 g and contains 3.01×10²³ water molecules. Each molecule has two H atoms, so the hydrogen-atom count is 6.02×10²³. The three atoms per molecule do not change the number of water molecules in the sample.
Check the conclusion and its limits
- A mole is a counting amount, not a fixed gram mass for every substance. Do not use Mr as if it already contained a gram unit. The Avogadro value refers to stated particles, and multiplying by the number of atoms in each molecule is a separate step.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
One mole of every substance has the same mass in grams. This claim is false: A mole is a counting amount, not a fixed gram mass for every substance. Do not use Mr as if it already contained a gram unit. The Avogadro value refers to stated particles, and multiplying by the number of atoms in each molecule is a separate step.
Higher Tier: moles connect mass to stated particles: State what is being counted. A mole of CO₂ molecules contains one mole of carbon atoms and two moles of oxygen atoms, three moles of atoms altogether. A mole of NaCl formula units corresponds to one mole of Na⁺ ions and one mole of Cl⁻ ions in the ionic lattice. Calling either sample simply a mole of particles without specifying which particles can make an answer ambiguous.
One mole of every substance has the same mass in grams.
A mole is a counting amount, not a fixed gram mass for every substance. Do not use Mr as if it already contained a gram unit. The Avogadro value refers to stated particles, and multiplying by the number of atoms in each molecule is a separate step.
The unit of amount containing 6.02×10²³ stated particles at the GCSE approximation: write the technical term.
mole means The unit of amount containing 6.02×10²³ stated particles at the GCSE approximation.