Lesson Plan - Get It!
Why do people renovate their homes? Why can't things stay the same?
Many people like to update their homes for a change of scenery or to improve the function of rooms in their house.
Sometimes during a renovation, larger problems with the home are exposed, leading to more work and structural changes. Chemical substances can also change, either physically or chemically.
Physical change for a substance involves changing the shape or appearance of the material, without changing the chemical composition. Analyze the image above; the substance is water. The chemical composition of water does not change, but the shape and phase do change. That indicates a physical change. Generally, physical changes can be reversed, meaning that you can change the substance back.
Crushing a sugar cube is another example of a physical change. The composition of the sugar hasn't changed, but the shape has been altered. The sugar could easily be compressed back into a cube.
- Did you know that adding sugar to water is considered a physical change?
Try putting a spoonful of sugar into a small glass of water. Leave the glass out overnight, and observe what is left tomorrow. The water evaporates off the solution, leaving the sugar crystals behind. You could scrape the crystals out and compress them back into the original sugar cube. Dissolving a single substance into water represents a physical change. If you used the sugar to make sweet iced tea, that would be a chemical change, because you have added another substance through brewing the tea with heat.
Chemical changes are not reversible, because you have changed the chemical composition of the substances. Burning wood in a fireplace is a good example of a chemical change. Once the wood has been converted to ash, you cannot reform the piece of wood.
Consider an egg.
- Do you think making scrambled eggs represents a physical or chemical change?
Cooking an egg is considered a chemical change, because you are actually changing the protein structure in the food. Think about how different a cooked egg and an uncooked egg appear.
- Do you think it possible to uncook an egg?
Physical and chemical changes impact every substance, those we use in our everyday lives and those that are only found in a laboratory. Physical changes can modify the appearance or shape of a substance, while chemical changes alter the composition or make-up of the material.
- Compare and contrast physical and chemical changes in a Venn diagram on a sheet of paper.
- Include at least three ideas for each.
In the Got It? section, you will practice identifying physical and chemical changes using an interactive.