Lesson 1: Understanding Chemical Reactions PDF

Lesson 1: Understanding Chemical Reactions A. Changes in Matter 1. A(n) physical change does not produce new substances. 2\. During a(n) chemical change, new substances form. a\. The starting substances and the substances produced have different physical and chemical properties. b\. A chemical r...

Lesson 1: Understanding Chemical Reactions A. Changes in Matter 1. A(n) physical change does not produce new substances. 2\. During a(n) chemical change, new substances form. a\. The starting substances and the substances produced have different physical and chemical properties. b\. A chemical reaction is a process in which atoms of one or more substances rearrange to form one or more new substances. B. Signs of a Chemical Reaction 1\. Sometimes, changes in physical properties, such as color or odor, indicate a chemical reaction. a. Formation of bubbles of a(n) gas can also be a sign of chemical reaction. b\. A solid formed when two liquids are mixed is called a(n) precipitate and can be evidence of a chemical reaction. 2\. A change in energy is another sign that a chemical reaction has occurred. a\. Thermal energy is absorbed or released during a chemical reaction and is evidenced by warming or cooling. b. Light energy might also be released during a chemical reaction. 3\. The only way to be certain a chemical reaction has taken place is to compare the chemical properties of the substances before and after the change. C. What happens in a chemical reaction? 1. During a chemical reaction, atoms of elements or compounds rearrange and form new elements or compounds. 2\. Atoms rearrange when chemical bonds between atoms break. D. Chemical Equations 1. A(n) chemical equation is a description of a reaction using element symbols and chemical formulas. 2. Element symbols represent elements. a\. Symbols of elements are shown on the periodic table. b. When an element exists as a(n) diatomic molecule, the element symbol is followed by the subscript 2. 3\. Chemical formulas represent compounds. a. A chemical formula contains element symbols and subscripts to describe the makeup of a compound.. b. When chemical formulas differ, they represent different substances (or compounds). 4\. A chemical equation includes the substances that react and the substances formed. a\. Reactants are the starting substances in a chemical reaction. b\. Products are the substances produced by a chemical reaction. c. In a chemical equation, the reactants are written to the left of an arrow, and the products are written to the right of the arrow. d\. Two or more reactants are separated by plus signs, as are any two or more products. E. Conservation of Mass 1. The law of conservation of mass states that the total mass of the reactants before a chemical reaction is the same as the total mass of the products after the chemical reaction. 2\. Mass is conserved in a chemical reaction because atoms are conserved. 3\. To show that mass is conserved, a chemical equation must show that the number of each type of atom must be balanced, or the same on both sides of the equation. a\. Chemical equations are balanced by adding coefficients. b\. A coefficient is a(n) number placed in front of an element symbol or a chemical formula in an equation. Lesson 2: Types of Chemical Reactions A. Patterns in Reactions 1\. There are four major types of chemical reactions. 2. Each type of chemical reaction follows a unique pattern in the way atoms in reactants rearrange to form products. B. Types of Chemical Reactions 1\. Knowing the types of chemical reactions helps predict how substances will react and what products will form. 2\. In a(n) synthesis reaction, two or more substances combine. a\. The product in a synthesis reaction is a(n) compound. b\. A synthesis reaction has two or more reactant(s) and one product(s). 3\. In a(n) decomposition reaction, a substance breaks down and forms two or more substances. a\. The reactant in a decomposition reaction is a(n) compound. b. The products in a decomposition reaction can be elements or compounds. c\. A decomposition reaction has one reactant(s) and two or more product(s). 4\. In a(n) replacement reaction, an atom or group of atoms replaces part of a(n) compound. 5\. One type of replacement reaction is single replacement. a\. In a(n) single-replacement reaction, one element replaces another element in a compound. b\. The reactants in this type of reaction are a(n) element and a(n) compound. c\. The products in this type of reaction are a different element and a different compound. 6\. The other type of replacement reaction is double replacement. a\. In a(n) double-replacement reaction, the negative ions in two compounds switch places, forming two new compounds. b\. The reactants in this type of reaction are two compounds. c\. The products in this type of reaction are two new compounds. 7\. In a(n) combustion reaction, a substance combines with oxygen and releases energy, usually in the form of thermal energy and light energy