6th Grade Science / Lesson 5 - Things Change
What will we be learning today?
How Can Things Change and Still Stay the Same?
Sounds like a riddle, doesn't it? However, when heat turns a solid into a liquid or a liquid into a gas, the identity of the substance is unchanged. For example, ice, liquid water, and water vapor are all forms of the same substance-water. Simply removing heat from water vapor (that is, cooling it off) turns it back into liquid water. Removing more heat turns the liquid water back into ice. This is an example of a physical change. A physical change is a change in size, shape, or state without forming a new substance.
Gallium has a low melting point for a metal. Body temperature is enough to turn it into a liquid. The change of state is a physical change. The liquid and solid metals are both pure gallium. Mixing things together, like water and the powdered drink, is a type of physical change. Neither the water nor the powder are turned into new substances when the drink is made. This physical change is a simple change of form. The wood keeps its identity but is cut into much smaller pieces by the violin maker. Let's Review What We Learned Today!