Chem Talk Chp 4 Section 1

In our lab, my group had to execute Method 2 to produce CO2. We mixed calcium carbonate and HCl to make CO2 gas. 

When matter goes through a change, there is most likely a change in energy involved. The energy will move from being stored in one form or placed to another form or place. If the matter involved loses energy in a change it has to go somewhere. Likewise, if the matter involved gains energy, the energy must come from somewhere. For example, heat energy. Is heat energy gained or lost when a change happens? If heat energy goes in, the chemicals gain energy and if heat energy is released the chemicals lose energy. A good way to understand energy change is with water. When you go from ice to vapor it is gaining energy and as you go from vapor to water it is losing energy. 

There are bonds holding a molecule together (bonds are within the molecule) and attractive forces holding molecules together. Bonds hold the atoms in a molecule together. Attractive forces are between molecules in a solid and liquid and they hold together the molecules so the solid and liquid do not separate. It takes heat energy input to break bonds between ions in materials and to break apart the forces. It does not matter if you are breaking chemical bonds or intermolecular forces of attraction, they both need an input of energy. 

There are “positive” and “negative” energy changes. To determine this we look from perspective of the reactants. There are endothermic changes and exothermic changes. Endothermic changes absorb heat energy whereas exothermic changes release heat energy. The method my group used to create CO2 gas was an exothermic reaction. 

When a change occurs there is a change in how the particles are made up in the matter. Chemists choose to measure the disorganization. The more spread out the particles are the more disorder there is. Therefore when a substance goes from a solid to liquid to a gas it increases in disorder. Chemists call this entropy. Entropy uses the symbol, S, and it shows tells us the disorder of particles in a substance. 

Leave a Reply

Your email address will not be published. Required fields are marked *