In a chemical change, new substances are formed. This is the key difference between chemical and physical changes. Students will need to be aware of the indicators of whether or not a chemical reaction has occurred. In this activity, students will create a spider map identifying and illustrating the signs of a chemical change.
A change in color is a sign that a chemical change might be taking place. An example of a reaction which causes a color change is the rusting of iron. In this reaction, iron reacts with oxygen in the presences of water. The iron oxide that forms is an orange/brown color, different to the gray metallic color of the iron.
If a gas is produced, then a chemical reaction has occurred. A clear sign of this is bubbles in a liquid. This isn’t to be confused with boiling, as boiling is a physical change.
A change in temperature, either an increase or decrease, can indicate a chemical reaction has occurred. When energy is released, the reaction can be described as exothermic. When energy is taken in, the reaction can be described as endothermic.
Sometimes when two liquids are combined, a solid can form. This solid is known as a precipitate and can fall to the bottom or can make the previously clear liquid cloudy.
If there is a noticeable odor after the reaction has occurred, then this could indicate a chemical change has happened. An example of this is milk turning sour.
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Student Instructions
Create a spider map about the indicators of chemical change.
(You can also create your own on Quick Rubric.)
| Proficient 33 Points | Emerging 16 Points | Beginning 0 Points | |
|---|---|---|---|
| Examples | There are at least five cells each giving an example of an indicator of chemical change. | There are at least three cells each giving an example of an indicator of chemical change. | There are a least two cells giving an example of an indicator of chemical change. |
| Illustration | The storyboard cell clearly illustrates indicator example. | The storyboard cell relates to the indicator example but is difficult to understand. | The storyboard cell does not clearly relate to the indicator example. |
| Evidence of Effort | Work is well written and carefully thought out. | Work shows some evidence of effort. | Work shows little evidence of any effort. |
