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Chemical Reactions

Science, Grade 8

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© Copyright NewPath Learning. All Rights Reserved. 94-4805 www.newpathlearning.com + + + + + C + O2 ➞ CO2 2H2 + O2 ➞ 2H2O 2H2O ➞ 2H2 + O2 Zn + 2HCl ➞ ZnCl2 + H2 NaCl + AgF ➞ NaF + AgCl H2O C6H12O6 Potassium chloride added to a silver nitrate solution forms a solid precipitate. Chemical Reactions Signs of Chemical Reactions A chemical reaction is a process in which one or more substances change to produce one or more new ones. Chemical reactions happen all around us – lighting a match, rusting of an iron bar, or the tarnishing of a silver spoon. Chemical Formulas A chemical formula uses symbols to identify the elements in a compound and the number of atoms of each kind present in a molecule. A water molecule is made up of 2 atoms of hydrogen bonded to 1 atom of oxygen. A glucose molecule is made up of 6 atoms of carbon, 12 atoms of hydrogen, and 6 atoms of oxygen. Chemical Equations A chemical equation uses chemical formulas and symbols to describe a chemical reaction. The starting materials in a chemical reaction are reactants. The resulting substances from a reaction are products. The reactants are always placed on the left of the arrow, and the products on the right of the arrow. Types of Chemical Reactions Synthesis Reaction In a synthesis reaction, two or more simple substances combine to form a compound. For example, hydrogen gas combines with oxygen gas to produce water! Decomposition Reaction In a decomposition reaction, a compound breaks down into its simpler parts. A decomposition reaction is the reverse of synthesis reaction. For example, water decomposes to form hydrogen gas and oxygen gas. Replacement Reaction Single Replacement In a single replacement reaction, a single uncombined element replaces another in a compound. The products of such a reaction are a new compound and a different element. For example, zinc replaces the hydrogen in hydrochloric acid to form zinc chloride and hydrogen gas. Double Replacement In a double replacement reaction, ions from two compounds switch places to form two new compounds. For example, silver nitrate reacts with sodium chloride to form two new compounds - silver chloride and sodium fluoride. water color change gas formation solid formation glucose reactants reactant + reactant ➞ product reactant ➞ product + product reactant + reactant ➞ product + product reactant + reactant ➞ product + product product A gas is formed when copper is added to nitric acid. These simple shapes combine to form a new object. The fish shape breaks down into simpler forms. NaOH, added to Phenol- phthalein solution causes a color change. NaOH

© Copyright NewPath Learning. All Rights Reserved. 94-4805 www.newpathlearning.com + + + + + Zn + 2HCl ➞ ZnCl2 + H2 H2O C6H12O6 NaCl + AgF ➞ NaF + AgCl 2H2O ➞ 2H2 + O2 reactant ➞ product + product reactant + reactant ➞ product + product reactant + reactant ➞ product + product 2H2 + O2 ➞ 2H2O reactant + reactant ➞ product Chemical Reactions Signs of Chemical Reactions What is a chemical reaction? ____________________________ _____________________________________________________ _____________________________________________________ Chemical Formulas A chemical formula uses ____________________ to identify the ____________________ in a compound and the ______________________________ of each kind present in a molecule. A water molecule is made up of _______ atoms of ____________________ bonded to _______ atom of ____________________ . A glucose molecule is made up of _______ atoms of ___________________ , _______ atoms of ___________________ , and _______ atoms of ____________________ . Chemical Equations A chemical equation uses ____________________ ____________________ and ____________________ to describe a chemical reaction. The starting materials in a chemical reaction are ____________________ . The resulting substances from a reaction are ____________________ . The ____________________ are always placed on the left of the arrow, and the ____________________ on the right of the arrow. Types of Chemical Reactions Synthesis Reactions Describe a synthesis reaction: ___________________________________ ___________________________________ ___________________________________ ___________________________________ Decomposition Reactions Describe a decomposition reaction: _____________________________________ _____________________________________ _____________________________________ _____________________________________ _____________________________________ Replacement Reactions Single Replacement Describe a single replacement reaction: _____________________________________ _____________________________________ _____________________________________ _____________________________________ _____________________________________ Double Replacement Describe a double replacement reaction: _____________________________________ _____________________________________ _____________________________________ _____________________________________ water glucose These simple shapes combine to form a new object. The fish shape breaks down into simpler forms. C + O2 ➞ CO2 Key Vocabulary Terms • atom • chemical equation • chemical formula • chemical reaction • compound • decomposition reaction • double replacement reaction • element • product • reactant • single replacement reaction • synthesis reaction Synthesis Reaction Decomposition Reaction Replacement Reaction \|xiBAHBDy01799ozX

Chemical Reactions

Science, Grade 8

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