Physical changes involve the change in states of matter. The states of matter, sometimes called its phase, include solids, liquids, or gases. During a physical change no new substance is created. The matter may take on a different form or state. The size, shape, and color of matter may also change. During a physical change, though, the molecules of a substance will stay the same.
Crushing a can, breaking a glass and chopping wood are all changes in the shape and size of an object. Stepping on a can and crushing it has forced a physical change. However, only the shape of the can has changed. It wasn't a change in the state of matter because the energy in the can did not change, meaning it was not melted or turned into a gas. The molecules that make up the can are still the same molecules. Breaking the glass and chopping the wood have forced a physical change as well.
When an ice cube is melted a physical change takes place because the temperature changed. The air temperature was warm enough to change the ice cube from a solid to liquid. Due to the changing temperature of the water, the boiling water was changed to a water vapor, or a liquid to a gas. Freezing the water is also a physical change because the liquid, water, was changed to a solid, ice. The change in temperature caused the physical change. In all three examples, the change in temperature caused a physical change. The water molecules are still water molecules.
A candle is made of wax and the heat from a lit flame will cause a temperature change, which allows the wax to melt, or change the phase from solid to liquid. The candle's size is also smaller, and the shape will change, too. Glass is formed by the hardening of a substance, changing a liquid to a solid, another phase change. The shape and color will also be physical changes caused by the temperature change. When a person paints their house or fence, the paint being brushed onto the objects is a physical change because the color of the fence has changed. In each of these examples, an object's size, shape, or color was changed. All are examples of physical changes.
Evaporation happens when atoms or molecules escape from a liquid and turn into a vapor. This is a physical change because the molecules of the matter change from a liquid to a gas. Evaporation can happen with any type of liquid. When temperatures are higher a liquid may evaporate faster. Evaporation is a physical change.
When two or more substances are joined together without the molecules changing it is called a mixture. When different colors of candies are joined together it is an example of a mixture. None of the molecules of the candy change, so this is also a physical change. Water and sand is also a mixture for the same reason. Other similar mixtures include salads, trail mix, and cereal with bananas.
Solutions are groups of molecules that are mixed together and evenly distributed in a substance. A pitcher of the fruit drink is an example because powder added to the water is spread out evenly throughout the water. Using syrup to make chocolate milk is also a solution. The molecules of the liquid and the drink mix are joined together to create the fruit drink or chocolate milk. A solution is also an example of a physical change.
In summary, there are many different kinds of physical changes which can include size, temperature, shape, color, and others. Two common types of physical changes are mixtures, when two types of molecules are joined together; and solutions, when the molecules are spread out evenly between two substances.
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