Chemical Reactions Chapter 21: Sec 1&2

Chemical Reactions a change of one or more substances converted into new substances Ex. Iron mixed w/ the oxygen in the air to form rust

Chemical Reactions Reactants – substances that combine or change Products – new substances that are produced Reactants Products

Butt of the arrow are the reactants and point of the arrow is the products Reactants Products Produce

Conservation of Mass A law which states that, in a chemical reaction matter is not created or destroyed; it stays the same French chemist Antoine Lavoisier experimented with mercury (II) oxide and heat found mass of products (liquid mercury and oxygen gas) equaled the mass of reactants Mass of reactants = mass of products

Writing equations chemical equation – uses chemical formulas and symbols to describe a chemical reaction and the product(s) it produces

Chemical Equations Chemical formula express the relationship between the elements in the compounds and molecule they make up Coefficients – numbers which represent the number of units of each substance in a reaction Knowing coefficients of chemical reactions allows chemists to use the correct amounts of reactants to predict the amounts of products Subscripts – numbers which represent the number of atoms in a molecule of a particular element

Symbols used in chemical equations Meaning produces or forms + Plus (s) solid (l) liquid (g) gas (aq) aqueous, a substance is dissolved in water heat the reactants are heated light the reactants are exposed to liqht elec. an electric current is applied to the reactants

Balanced Equations both sides of the equation have same number of atoms of each element (remember law of conservation of mass) Coefficients used to balance the amount of reactants and products

Writing balanced equations describe the reaction in words write the equation using formulas and symbols check for balance add coefficients where needed for balance