Chemical Reactions PDF
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Southdowns College
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This document contains notes on chemical reactions, including different types of chemical reactions, definitions, examples, and class activities. It also includes a section on balancing chemical equations.
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CHEMICAL REACTIONS CHAPTER 3 WHAT? A chemical reaction is when substances react with each other to form new substances with different chemical properties. DEFINITIONS Reactants: the substances that react with one another Products: the substances that are made or produced Chemical Change: a chem...
CHEMICAL REACTIONS CHAPTER 3 WHAT? A chemical reaction is when substances react with each other to form new substances with different chemical properties. DEFINITIONS Reactants: the substances that react with one another Products: the substances that are made or produced Chemical Change: a chemical reaction causes new products to be formed Physical Change: a phase change occurs Phase Change: a substance changes its phase but does not change its chemical form. PARTS OF A CHEMICAL REACTION Every reaction has reactants and products Reactants → substances that react with one another Products → substances that are made or produced HOW TO TELL IF A CHEMICAL REACTION IS TAKING PLACE: There is a colour change A gas is being produced (look for bubbles or fizzing) It feels hot or cold (exothermic or endothermic) A smell is present EXAMPLES CLASS ACTIVITY Chemical Change Sign of chemical change Burning wood Rotting fruit Baking a cake Rusting Metal Using a battery Digestion Souring Milk Exploding fireworks Cooking an egg CLASS ACTIVITY Chemical Change Sign of chemical change Burning wood Heat Rotting fruit Smell Baking a cake Colour change Rusting Metal Colour change Using a battery Heat Digestion Bubbles or fizzing Souring Milk Smell Exploding fireworks Colour change Cooking an egg Smell HOMEWORK Revision Pg 48 classify exercise the substances question 1-4 CHEMICAL CHANGE Chemical change: when new products are formed. In a chemical reaction old bonds between reactants are broken and new bonds between products are formed. Resulting in a new product / new molecule. Example: Rust PHASE CHANGE Physical change: when a phase changes occurs. The molecule remains the same and it can return to its original form. Example: water changing to steam ENERGY CHANGES EXOTHERMIC REACTIONS ENDOTHERMIC REACTIONS More energy is given out than what is More energy has to be put into the required reaction than what is given out. Energy is lost to the surroundings The product is warmer than the reactants The product is much colder than the Energy is often taken from the surrounding reactants for these reactions Example: a candle burning Example: baking bread TYPES OF CHEMICAL REACTIONS 1. Combustion 2. Synthesis 3. Acid base-reactions 4. Decomposition reaction COMBUSTION Oxygen combines with a compound to form carbon dioxide and water. Fuel + O2 → CO2 + H2O SYNTHESIS A chemical reaction where two molecules interact to form a different molecule. A + B → AB ACID-BASE A chemical reaction that occurs between an acid and a base. Acid + Base → H2O + Salt DECOMPOSITION A chemical reaction where a reactant breaks down into two or more products. AB → A + B HOMEWORK Complete the exercise on page 51 Research examples on exothermic and endothermic reactions on pg 55 BALANCING CHEMICAL EQUATIONS IS THIS EQUATION BALANCED? The equation is 𝑂2 + 𝐶 → 𝐶𝑂2 balanced if the reactants = Element Reactants Products products O C BALANCE THE EQUATION: EX 1 YOU CAN’T 𝑀𝑔 + 𝑂2 → 𝑀𝑔𝑂 CHANGE THE SUBSCRIPTS Element Reactants Products Mg O BALANCE THE EQUATION: EX 2 YOU CAN’T 𝐿𝑖 + 𝐹2 → 𝐿𝑖𝐹 CHANGE THE SUBSCRIPTS Element Reactants Products H O BALANCE THE EQUATION: EX 3 YOU CAN’T 𝐻2 + 𝑂2 → 𝐻2 𝑂 CHANGE THE SUBSCRIPTS Element Reactants Products H O HOMEWORK Complete balancing equations worksheet.