Assuming that they do have a fixed shape to start with, when they are subject to heat or force. The forces could be compression, extension or deforming stress.
Pressure can cause objects to change shape
adjustment handle
To be able to bend or change the objects shape
adjustment handle
the lens of our eyes is different to the lens of a magnifying glass-it can change its shape from thick to thin
Group of objects that keeps it shape
Pressure could cause objects to deform.
What objects have a hexagon shape?
Forces can stop or start an object in motion, or change its velocity. They can also change the shape of objects.
Direction or shape
A physical change occurs when substances or objects undergo a change that does not alter their chemical configuration. Physical changes include a change in shape or form.
The lens