physics

Parachor

Parachor is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Parachor rather than just read about it. In short: Parachor is a quantity related to surface tension that was proposed by S. Sugden in 1924.

Key takeaways

Parachor belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Parachor to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Parachor from memory before moving on to harder problems.

Reference excerpt

Parachor is a quantity related to surface tension that was proposed by S. Sugden in 1924. It is defined according to the formula:

P = γ 1 / 4 M / ( ρ L − ρ V ) {\displaystyle P=\gamma ^{1/4}M/(\rho _{L}-\rho _{V})} , where γ {\displaystyle \gamma } is the surface tension, M {\displaystyle M} is the molar mass, ρ L {\displaystyle \rho _{L}} is the liquid density, and ρ V {\displaystyle \rho _{V}} is the vapor density in equilibrium with liquid. Parachor has a volume multiplier and is therefore extensible from components to mixtures. Parachor "has been used in solving various structural problems." The etymology of parachor is from a combination of prefix para "para," meaning "aside," and Greek "chor," meaning "space." Sugden in other publications showed that each compound had a characteristic parachor value. Since the work of Sugden, parachor has been used to "correlate" the surface tension data of a variety of pure liquids and liquid mixtures. Boudh-Hir and Mansoori (1990) presented a general molecular theory for parachor valid for all ranges of temperature. Using the molecular theory of Boudh-Hir and Mansoori, Escobedo and Mansoori (1996) produced an analytical solution for parachor, as a function of temperature valid in all temperatures ranging from melting point to critical point. They also used the resulting analytic equation to predict surface tensions of a variety of liquids in all ranges of temperature from melting point to critical point. It is shown to represent the experimental surface tension data of 94 different organic compounds within 1.05 AAD%. This analytic equation represents an accurate and generalized expression to predict surface tensions of pure liquids of practical interest. Escobedo and Mansoori (1998), extended applications of the same theory to the case of mixtures of organic liquids. Using the proposed equation surface tensions of 55 binary mixtures are predicted within an overall 0.50 AAD% which is better than all the available prediction and correlation methods. When the resulting equations are made compound-insensitive using a corresponding states principle, the surface tension of all the same 55 binary mixtures are predicted within an overall 2.10 AAD%. It is shown that the proposed model is also applicable to multicomponent liquid mixtures.

Surface Tension of Binary Mixtures The surface tension of binary carbon dioxide mixtures was predicted using a modified parachor approach that took temperature-dependent characteristics into account. Individual solvent parachors rise almost linearly with decreasing temperature. The exponent of the parachor equation drops consistently as the temperature is decreased for all binary mixtures.

References

Worked examples

Example 1 — a first encounter with Parachor

Start with the simplest possible case. Write down what Parachor claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Parachor before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Parachor ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Parachor

In research: Parachor appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Parachor in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Parachor is common in secondary-school and first-year university syllabi. It links to neighbouring topics Fluid mechanics, so understanding it makes those chapters shorter.
In everyday life: Look for Parachor outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Parachor in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Parachor means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Parachor out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Parachor in simple terms?

Parachor is a quantity related to surface tension that was proposed by S. Sugden in 1924.

Why does Parachor matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Parachor?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Parachor.