Attraction between particles, a question

[Anna AylingParticipant]

Question: In the K-2 book, lesson A4 at the bottom of page 59 the question is asked, “What makes the difference between a substance being a solid, liquid, or a gas?”

Turn the page and it says, “It is the degree to which the individual particles of the substance are attracted to one another.”

Then in the last but one paragraph from the end of page 60 it says, “..this tendency of the particles to jiggle and move about increases with temperature, but, the strength of the attraction between particles, remains unchanged.”

I don’t understand how those two things go together. If the temperature increases and particles are jiggling more then eventually the solid (let’s say it was a solid to start with) becomes a liquid and then the strength of/degree to which the particles are attracted becomes less, right? Because particles in a liquid are less attracted to each other than in a solid (which we’ve just established on page 60). So why does it say that the strength of the attraction between particles remains unchanged with temperature? Help!

[Bernard NebelKeymaster]

Reflecting on your question, I believe the point of confusion, which I did not make clear, is this. The attraction between particles is commonly a magnetic attraction, an attraction between positive and negative charges. Visualize actual magnets. You readily experience that the attraction between magnets, or between a magnet and iron, rapidly decreases with distance. When magnets are a few inches or more apart, you don’t feel their mutual attraction at all; when they are only a hair’s breadth apart, you feel it strongly. Note that it is not the nature of the attractive force that is changing; it is simply that the nature of that force is such that the strength of attraction deceases rapidly with distance.

Coming back to the lesson and particles, the increased jiggling that occurs with increasing temperature pushes the particles further apart. Thus, you are right, the attraction between them becomes less. Hence, they begin to slip and slide about each other (liquify) or go off independently (become gas). But again, it is not because the nature of attraction has changed; it because the increased jiggling has pushed them further apart where there is less attraction.

Thank you for your question. I hope this clarifies it. Do ask again as you need.

• This reply was modified 7 years ago by  Bernard Nebel.

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