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.
Engage students by letting them see chemical change indicators firsthand with safe, easy-to-set-up experiments. Hands-on activities help students connect theory to real-world observations, making the learning experience memorable and meaningful.
Use readily available items like vinegar, baking soda, steel wool, lemon juice, or milk. Collecting familiar materials makes setup simple and reduces classroom costs.
Show color change with rusting steel wool in vinegar, gas production with baking soda and vinegar, temperature change with a baking soda and calcium chloride reaction, precipitation with mixing Epsom salt and dish soap, and odor change by letting milk sour. Assign groups to different indicators for active participation.
Encourage close observation of changes, such as new smells, bubbles, color shifts, or temperature differences. Have students jot down their findings in science notebooks or on a worksheet.
Ask students to share what they noticed and connect their results to the indicators discussed. Clarify misconceptions and reinforce how each experiment demonstrates a specific chemical change indicator.
Indicators of a chemical change include color change, production of gas (bubbles), temperature change (energy released or absorbed), formation of a precipitate (solid), and noticeable odor. These signs help students identify when a new substance has formed during a reaction.
A chemical change creates new substances with different properties, while a physical change only alters the appearance or state of a material without changing its identity. For example, rusting is chemical, melting ice is physical.
Have students create a spider map that identifies, illustrates, and describes the signs of chemical change—such as color change, gas production, temperature shift, precipitate formation, and odor. This visual tool helps reinforce learning.
A color change often means a new substance with different properties has formed, which is a key sign of a chemical reaction. For example, when iron rusts, it changes from gray to orange-brown due to iron oxide forming.
Gas bubbles from a chemical change appear during a reaction and mean a new substance is forming, such as fizzing during vinegar and baking soda mixing. Boiling, however, is a physical change caused by heating a liquid, not by creating a new substance.