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Chemical Properties and Changes

This lesson explores key concepts of chemical properties and changes, defining characteristics that can be observed as substances transition into different forms. It outlines the processes of chemical change, highlighting indicators such as color change, gas formation, and energy release. Additionally, the lesson covers balancing chemical equations and the principles of reaction rates, including the effects of temperature, concentration, and surface area. Through practical examples like baking cookies and the reaction of fireworks, students gain insight into the transformation of matter and chemical reactions.

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Chemical Properties and Changes

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  1. Chemical Properties and Changes Chapter 7 Lesson 4

  2. Chemical Property • A characteristic of matter that can be observed as it changes to a different type of matter • Ability to burn • Ability to rust • Ability to rot/decompose

  3. Chemical Change • A change in matter in which the substances that make up the matter change into other substances with new physical and chemical properties • Oxygen + iron = rust

  4. Signs of Chemical Change • Formation of bubbles • Change in color, odor, or energy • Do not always indicate a chemical change • Water boiling produces bubbles  physical change in state • Only proof is the formation of a new substance

  5. Do you think a chemical change occurs when you bake cookies? Why or why not? • What signs show that a chemical change takes place when fireworks explode?

  6. Explaining Chemical Reactions • When atoms bond together in new formations • Often called chemical changes

  7. Chemical Equation • Shows the chemical formula of each substance in the reaction • Formula on left of arrow – reactants • Formula on right of arrow – products (new substances present after reaction) • Arrow indicates a reaction has taken place

  8. Balancing Chemical Equations • Conservation of mass (total mass before and after reaction is the same) • # of atoms of each element before a reaction = # of atoms of each element after a reaction • You cannot change the chemical formulas • Changing formula changes identity of substance • Place coefficients (multipliers) in front of formulas • Change the amount of the reactants and products

  9. The Rate of Chemical Reactions • Higher temperature = increases rate of reaction • Particles move faster, collide with greater force and more frequently • Frying eggs at a higher temperature happens more quickly • Concentration – the amount of substance in a certain volume • Faster if concentration of at least 1 reactant increases • More particles available to bump and react • Acid rain damages statues more quickly than normal rain

  10. The Rate of Chemical Reactionscontinued • Surface Area • Smaller pieces have more total surface area = more space available for reactants to collide • A broken antacid tablet will react more rapidly than a whole antacid tablet dropped into water.

  11. Chemistry • Matter • Arrangement of atoms • Physical properties • Chemical properties • Physical changes • Chemical changes

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