Full
Chemistry
Introduction
Objective:
The goal of the chemistry unit is to teach students how to identify when a chemical reaction has occurred. The students should be able to watch a process and determine if a chemical reaction has occurred. They will see (and usually perform) reactions demonstrating every type of chemical change.
Background:
Chemistry is the study of chemical reactions as a result of molecular interaction. There are four ways to determine if a chemical reaction has occurred.
Heat is transferred:
The chemicals will change temperature when a reaction occurs. If the chemicals feel warmer then the reaction is exothermic, heat is going out of the system. If the chemicals feel colder then the reaction is endothermic, heat is going into the system. Most spontaneous reactions are exothermic, but the reaction between Epsom salts and water is a simple endothermic reaction. Combustion is an exothermic reaction that usually requires some activation energy, such as lighting it with a match.
A gas is released:
These are usually visible reactions because they will start to bubble. A safe and simple example of this is the reaction between baking soda and vinegar. These two chemicals (sodium bicarbonate and acetic acid) react and release carbon dioxide.
A color change occurs:
Combining chemicals can change the pigmentation that gives the chemicals color. A change in the pigments will cause the light to reflect differently and a color change to occur. Testing for pH is an example of a color changing reaction. The pH of the solution will change the pigment on the litmus paper or in the indicator. Acids and bases change the pigments in different ways, which causes the indicator to change different colors depending on the pH.
A precipitate is formed:
A chemical reaction has occurred if two liquids are poured together and a solid (called a precipitate) is formed. This happens when the two chemicals react to form something that is not
Introduction
Objective:
The goal of the chemistry unit is to teach students how to identify when a chemical reaction has occurred. The students should be able to watch a process and determine if a chemical reaction has occurred. They will see (and usually perform) reactions demonstrating every type of chemical change.
Background:
Chemistry is the study of chemical reactions as a result of molecular interaction. There are four ways to determine if a chemical reaction has occurred.
Heat is transferred:
The chemicals will change temperature when a reaction occurs. If the chemicals feel warmer then the reaction is exothermic, heat is going out of the system. If the chemicals feel colder then the reaction is endothermic, heat is going into the system. Most spontaneous reactions are exothermic, but the reaction between Epsom salts and water is a simple endothermic reaction. Combustion is an exothermic reaction that usually requires some activation energy, such as lighting it with a match.
A gas is released:
These are usually visible reactions because they will start to bubble. A safe and simple example of this is the reaction between baking soda and vinegar. These two chemicals (sodium bicarbonate and acetic acid) react and release carbon dioxide.
A color change occurs:
Combining chemicals can change the pigmentation that gives the chemicals color. A change in the pigments will cause the light to reflect differently and a color change to occur. Testing for pH is an example of a color changing reaction. The pH of the solution will change the pigment on the litmus paper or in the indicator. Acids and bases change the pigments in different ways, which causes the indicator to change different colors depending on the pH.
A precipitate is formed:
A chemical reaction has occurred if two liquids are poured together and a solid (called a precipitate) is formed. This happens when the two chemicals react to form something that is not