Question
Solder is a silver metal used to hold pipes together when the solder is heated it melts and acts as a type of metal glue. Mrs. Hanley heats a piece of solder until it melts between two pipes what best identifies the point at which a physical change first takes place?
A) when the solder melts
B) when the solder cools down
C) when the solder is a soft metal
D) when the solder becomes solid again
Answer:
The correct answer is A)
Explanation:
The question is a good one. It asks to know when the PHYSICAL change first takes place. It means that it is possible to have changes to the Solder that is not immediately visible to the eye.
When any object is heated, its molecules vibrate even faster causing the bonds holding them to expand. This invariably leads to an expansion of the object. In the case of metals, metals when heated to a degree can actually become liquid.
The solder in this case has expanded before it melts. The melting is however easy to see more than the expansion of the molecules that make up the metal.
Metals when they melt do not assume the shape they were prior. When they cool off, they become as strong as they were before thus the binding quality of the solder in this case. However, they can only take the shape of the container they are poured into or the shape they were melted into if it was not containerized.
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