Assignment #5 Temperature in Reactions LO: To determine which solute dissolves most endothermically and exothermically in water. EQ: What makes an endothermic reaction feel cold? (explain using bonds and movement of heat) AGENDA 1. Discussion 2. Exploration HOMEWORK 1. Finish old processing tasks LEVEL ZERO VOICE CATALYST (10 minutes, individual work): 1. When bonds are broken energy is. When bonds are formed energy is. (absorbed or released) 2. Using bond energies explain why exothermic reactions feel hot. (include terms reactants and products) 3. Count the atoms: Ca(NO 3 ) 2 4. Count the atoms in this reaction. Is it balanced? Mn + HI H 2 + MnI 3
Why do cold packs get cold?
It takes energy to break bonds between molecules or ions Energy is released when bonds are formed If it takes more energy to separate reactants than to form products: endothermic
If it takes more energy to separate reactants than to form products: endothermic Endothermic: Energy to separate reactants > energy released by products formed
Exothermic: Energy to separate reactants < energy released by products formed
Intro: Potassium chloride is a common salt substitute. Calcium chloride is used to absorb moisture from the air. It is also included in some ice-melt mixtures to treat icy sidewalks during winter. Sodium carbonate is a common ingredient in detergents for dishwashing machines. Sodium bicarbonate, also known as baking soda, is used in baking, in toothpaste, and numerous other applications.
During this assignment you will be investigating potassium chloride, calcium chloride, sodium carbonate, and sodium bicarbonate to find out which is most exothermic and most endothermic when dissolved in water. How can we set up a fair comparison to find out which solute is the most endothermic and which is most exothermic when dissolved in water?
During this assignment you will be investigating potassium chloride, calcium chloride, sodium carbonate, and sodium bicarbonate to find out which is most exothermic and most endothermic when dissolved in water. Variables to control: What are some variables you could control? How might you control them? Variable to change: What is the only variable that should Hypothesis: The solute will be the most exothermic. The solute will be the most endothermic.
Procedure: Amount of each solute: Amount of water: Potassium chloride Calcium chloride Sodium carbonate Sodium bicarbonate Initial Temp ⁰C Final Temp ⁰C Change in Temp ⁰C Endo/ Exo
Highlight the compound that dissolved the most endothermically and the most exothermically.
Energy is required to pull apart atoms and molecules. When atoms or molecules come together and form bonds, energy is released. It takes energy to break bonds, and energy is released when bonds are formed. Watch animation here: http://www.middleschoolchemistry.com/multime dia/chapter5/lesson9#breaking_and_making_b onds
When water molecules are attracted to and bond to molecules or ions, some energy is released. When water molecules pull apart the molecules, it takes energy. Watch animation here: http://www.middleschoolche mistry.com/multimedia/chap ter5/lesson9#energy_and_ dissolving
If less energy is released when water molecules bond to the solute than it takes to separate the solute, the dissolving is endothermic and the temperature decreases.
If more energy is released when water bonds to the solute than it takes to separate the solute, the dissolving is exothermic and the temperature increases.
ENERGY VS TIME GRAPHS
Assignment #5 Temperature in Reactions LO: To determine which solute dissolves most endothermically and exothermically in water. EQ: What makes an endothermic reaction feel cold? (explain using bonds and movement of heat) AGENDA 1. Discussion 2. Exploration HOMEWORK 1. Finish old processing tasks LEVEL ZERO VOICE PROCESSING TASK (10 minutes, individual work): Create a drawing/comic/model that illustrates the concept of endothermic and exothermic reactions. Must include bond energy. Is it chemical or physical? Must include title