When Particles Don't Stick
When particles don't stick teaches Grade 5 students why some substances refuse to dissolve, using molecular attraction as the explanation. For a solid to dissolve, liquid molecules must pull the solid particles apart. But if solid particles prefer each other more than they prefer the liquid, they clump together and refuse to separate. The absence of attraction between the solid and liquid means the particles remain as visible clusters instead of spreading into solution. This concept from Amplify Science (California) Grade 5, Chapter 2, connects molecular behavior to observable phenomena like sediment.
Key Concepts
Why doesn't everything dissolve? It comes down to attraction .
For a solid to dissolve, the liquid molecules have to pull the solid particles apart. But sometimes, the solid particles like each other more than they like the liquid. They clump together and refuse to separate. Because there is no attraction to pull them apart, they remain as visible clusters .
Common Questions
Why don't all substances dissolve in water?
For dissolving to occur, water molecules must attract and pull apart the solid particles. If the solid particles attract each other more strongly than the water attracts them, they stay together and refuse to dissolve.
What determines whether a solid dissolves?
The relative strength of attraction: if solid-to-liquid attraction is stronger than solid-to-solid attraction, the solid dissolves. If solid-to-solid attraction dominates, the solid clumps and doesn't dissolve.
What are visible clusters in a liquid?
Visible clusters are groups of solid particles that have stayed together rather than separating into solution. They appear as cloudiness, sediment, or floating particles in the liquid.
How does this explain why sand doesn't dissolve in water?
Sand particles attract each other more strongly than water attracts them. Water cannot pull the particles apart, so the sand remains as a cluster and eventually settles as sediment.
Is the failure to dissolve a chemical or physical property?
It is a physical property. No new substances are formed — the material simply stays together rather than mixing. Molecular attraction governs this physical behavior.
What grade and chapter covers why particles don't dissolve?
Grade 5, Chapter 2 of Amplify Science (California): Why do some salad dressings have sediments, and others do not?