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Chemical Properties and Changes

Chemical Properties and Changes. Chapter 7 Lesson 4. 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. Chemical Change.

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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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