Chemical Reactions Lesson for Kids: Definition & Examples

Instructor: Sandra Van Fleet
This lesson will define and describe examples of how to identify chemical reactions, along with showing the difference between chemical and physical changes.

What is Going On?

In your rush to make it to school on time, you start gulping that glass of milk you just poured. Ugg!! That was disgusting! What are those clumps and why does it smell? Believe it or not, you've just had a taste of a chemical reaction! Let's investigate this further.

To Change or Not to Change

The example given, the spoiled milk, is a chemical change. A chemical change or reaction is a change that creates something new. Now this may be confusing, because the milk is still milk. The difference is that the milk cannot change back to its original state. The chemicals inside the milk have changed and created something new. So if it cannot go back to the way it was, then it is something new and a chemical change has occurred.

This is different from a physical change where something might change shape or color or texture, but nothing new is created. A perfect example is an ice cube that has melted and is now water. Well, guess what? Before it was an ice cube, it was water. So, it has changed shape twice, but it is still water.

The rusty chain is an example of a chemical change. Air and water on metal creates rust, and if you ever left something metal outside you know that you cannot change it back.
rusted chain

Witnessing the Change

We have ways of knowing that a chemical reaction has occurred. With our milk example, we noticed that the milk did not look right. We also stated that the milk smelled different, and tasted strange. These are good ways of knowing that a chemical reaction has occurred. Changes in the way it looks, smells, tastes and even a change in color can show that a chemical reaction has occurred.

Another way to tell if a chemical reaction has occurred is to see the change. You may have added vinegar to baking soda at home or at school in your science class. When you added the vinegar to the baking soda, you watched as it started to bubble. The bubbles are filled with gas, which is a sign that a gas was created. Once the reaction stops, you cannot get your vinegar or baking soda back.

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