CHEMICAL AND PHYSICAL CHANGES OF MATTER Chemical Changes A chemical change is a change in which one kind of substance is changed into a different kind of substance. Chemical changes produce substances that were not there when you started. You can’t reverse or undo a chemical change. For example, burning a log is an example of a chemical change: once you burn a log, you can’t “unburn” it or reconstruct it from its ashes. Examples of chemical changes include: 1. rusting metal 2. digesting food 3. spoiled food Chemical Change Examples Chemical Change Event Substance/Item Before chemical change Substance/Item After chemical change car rusting steel rust burning paper paper ash frying an egg raw egg cooked egg Possible Signs a Chemical Change Has Taken Place: a change in color a change in the substance’s temperature light is given off a gas is produced a change in smell a change in taste (Warning: do not taste anything during a science experiment.) Lesson Checkpoint: What is a chemical change? Give one example of a chemical change. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Physical Changes A physical change is when matter undergoes a change that does not affect its physical make up. Physical changes involve an object’s physical properties such as size, shape, color, and weight. The substance or object involved is the same before and after the change (unlike a chemical change). The change is not permanent and can be undone. Examples of physical changes: 1. an ice cube melting 2. a piece of paper cut into two pieces 3. a crushed can Physical Changes Physical Change Event Substance/Item Before physical change Substance/Item After physical change grass being mowed grass grass glass broken glass glass butter being melted butter butter Signs a Physical Change Has Taken Place: change of shape change of state (solid, liquid, or gas) change in size change in any other physical property Lesson Checkpoint: What is a physical change? Give one example of a physical change. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Physical VS Chemical Changes: Which Is Which? Physical Changes Chemical Changes A paper towel is ripped in half. Milk goes sour. A ball of clay is molded into a square. A silver ring tarnishes. A stick is snapped in half. Bread is toasted. Stirring cake batter. Dead leaves and grass clippings turn into compost. Chemical Reactions Keep in mind: all matter is made of atoms, which may combine to form molecules A chemical reaction is when one or more substances change into different substances that have different chemical and physical properties. During chemical reactions, the atoms in the reactants rearrange to form products with different properties. For example, hydrogen can combine with oxygen to form water. Another example: vinegar + baking soda = carbon dioxide Words to know when dealing with chemical reactions: A reactant is a substance used in a chemical reaction. The product is a substance made during a chemical reaction. A chemical equation: reactant + reactant = product Lesson Checkpoint: What is a chemical reaction? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Types of Chemical Reactions: 1. Decomposition reaction is the process of a complex substance being split up into simpler substances. General formula to explain a decomposition reaction: AB A + B 2. Synthesis reaction is the process of two or more simple substances combining to form a more complex one. General formula for a synthesis reaction: A + B = AB Decomposition and synthesis reactions are opposites. 3. Combustion reaction is when all substances in a compound are combined with oxygen, which then produces carbon dioxide and water. So the equation for a combustion reaction is A + B + Oxygen = Carbon Dioxide + Water Because the product of combustion is ALWAYS water and carbon dioxide. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.