Separate Chemistry: cells produce a potential difference
Введено| English | Значение |
|---|---|
| chemical cell/ˈkemɪkl sel/ | химический элемент питания |
| battery/ˈbætəri/ | батарея |
What would explain this observation?
- Two different metal electrodes touching an electrolyte can produce a potential difference. This chemical cell 化学电池 supplies electricity, unlike electrolysis driven by an external power supply.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Chemical reactions in cells produce electricity. A simple cell consists of two different metals in contact with an electrolyte and connected through an external circuit. The electrolyte permits ionic movement, while electrons move through the metal wires. The voltage produced depends on electrode materials and the electrolyte. A battery 电池组 contains two or more cells connected in series to give a greater voltage when their polarities are aligned.
- chemical cell: A device whose chemical reactions produce electricity; battery: Two or more cells connected in series to provide a greater voltage.
What distinguishes the simple chemical cell from the electrolysis apparatus?
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A chemical cell GENERATES a potential difference from its own spontaneous reactions; electrolysis CONSUMES an external supply to force a reaction. Electrolytes conduct by ions, never by free electrons.
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
- Use supplied readings or reactivity information to compare cells under specified conditions. Do not promise a universal voltage from a metal pair alone: electrolyte choice and conditions also matter. Connecting identical cells in series adds their potential differences in the ideal stated model; reversed orientation subtracts one cell’s contribution. Voltage measures potential difference, not the amount of chemical reactant remaining or the rate of all reactions.
- For actual school work use approved metal strips and electrolytes, a high-resistance voltmeter and consistent exposed areas, separation, temperature and cleaning. Keep electrodes apart so they do not directly short together. Read the sign and magnitude with the stated meter connections. Do not attach a bench power supply to this generating-cell comparison or attempt to charge an unsuitable cell. Detailed commercial cell chemistry is not required by this section.
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: an original supplied table gives zinc–copper cell readings of 0.90 V in electrolyte A and 0.65 V in electrolyte B under stated conditions. This supports an electrolyte effect, not a claim about every zinc–copper cell. Three identical 0.90 V cells in aligned series give an ideal total of 2.70 V. Two aligned and one reversed would give 0.90 V in that simplified model.
Four identical 0.75 V cells are aligned in series. Find the ideal total voltage. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Four identical 0.75 V cells are aligned in series. Find the ideal total voltage.
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The result is 3 V. Known: four identical 0.75 V cells in series, aligned. Total = 4 x 0.75 = 3 V. Series voltages add; reversing one cell would subtract its voltage instead.
Check the conclusion and its limits
- The electrolyte does not carry free electrons in the same way as the wire. A battery is not just any one cell in this specification’s terminology. An externally powered electrolytic cell has a different purpose and electrode context. Do not transfer an electrode sign rule between the two apparatus without identifying how it is operating.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Electrode materials alone fix a cell’s voltage regardless of electrolyte. This claim is false: The worked table shows the same zinc-copper pair giving 0.90 V in one electrolyte and 0.65 V in another. The electrode metals set the tendency, but the electrolyte completes the chemistry and shifts the voltage.
Separate Chemistry: cells produce a potential difference: Use supplied readings or reactivity information to compare cells under specified conditions. Do not promise a universal voltage from a metal pair alone: electrolyte choice and conditions also matter. Connecting identical cells in series adds their potential differences in the ideal stated model; reversed orientation subtracts one cell’s contribution. Voltage measures potential difference, not the amount of chemical reactant remaining or the rate of all reactions.
Electrode materials alone fix a cell’s voltage regardless of electrolyte.
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The worked table shows the same zinc-copper pair giving 0.90 V in one electrolyte and 0.65 V in another. The electrode metals set the tendency, but the electrolyte completes the chemistry and shifts the voltage.
A device whose chemical reactions produce electricity: write the technical term.
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chemical cell means A device whose chemical reactions produce electricity.