| What are Exothermic and Endothermic reactions | Exothermic is a reaction that gives out energy. Endothermic is a reaction that takes in energy |
| Examples of Exothermic and Endothermic reactions | Exothermic: Burning a material with oxygen releases heat [energy] This makes combustion a exothermic reaction.
Endothermic: Baking a cake. Sodium bicarbonate gets broken down into sodium carbonate. water and Carbon dioxide which rises the cake. |
| How can reactions be Exothermic or Endothermic | Bonds breaking or creating. Breaking bonds in compounds requires energy. Creating bonds releases energy. If more bonds are broke then created, its endothermic. If more bonds are created then broke, its exothermic |
| How to test if the reaction was Exothermic or Endothermic | -The surrounding temperature can help us out.
-If its has increased, that means its exothermic.
-If its decreased in temperature, its endothermic.
-Another way is putting water under your beaker. I
-f it freezes, its endothermic [the reaction has to go below 0 degrees.] |
| What is the graph called to represent the reaction? | Its called a Energy profile. |
| What does it look like in Exothermic or Endothermic [energy profile] | -Exothermic would have reactants have more energy then the products. This is because energy is released. Its a n shape from reactants to products as it needs to reach Activation energy. This is the minimum amount of energy for the reaction to begin really.
-Endothermic is opposite. Reactants have less energy then the products as it takes in energy. its a n shape with again having activation energy. |
| Why do you need a certain amount of energy for the reaction to happen? | -Particles collide with each other for reactions to happen.
-Energy allows them to move faster and faster. |
| How to find out Bond energy? | Exams usually provide us with two things. The structure and the energy value. With that you can have compound and the energy needed to create/break them.
An example would be Hydrogen + Chlorine.
H--H + Cl--Cl = H-Cl. H--H=436 kj/mol, Cl--Cl=242 kj/mol H--Cl=431kj/mol
On the left hand side, we are breaking the bonds. The answer would be positive as because it requires energy. [678kJ] The right hand side is making bonds so it would be negative as it releases energy. [-862kJ] [678-862=-184kJ]
This reaction is Exothermic, as energy is being released [its negative] |
| What exactly is Activation Energy? Where is it shown on a Reaction Graph? | -This is simply the amount of energy needed to Break Bonds
-On the Reaction Profile, it is the Energy Difference between the Reactants, and the Highest Point on the Curve
-So if the Energy input isn't enough to hit the Activation Energy, nothing will happen |
| What happens in terms of Energy and Breaking/Making Bonds? | -When bonds need to be Broken, Energy has to be given in. This is an Endothermic Process [Energy is Used]
-When bonds need to be made, Energy is Released from it. This is an Exothermic Process [Energy is Given] |
| So in terms of Bond Energy, what happens in Exothermic and Endothermic reactions Always? | -If its an Exothermic Reaction, the Energy Released by making Bonds will be Greater than the Energy needed to Break them
-If its an Endothermic Reaction, the Energy Used will be Greater than the Energy Released from Making the Bonds |
| Formula of Overall Energy Change?
-What happens if the Result is
Positive
Negative | -Overall Energy Change = Energy Required to Break Bonds - Energy Released by forming Bonds
-If Positive, its an Endothermic Reaction
-If Negative, its an Exothermic Reaction |
