Every day, we see different kinds of reactions happening around us, even if we don’t always notice them. These reactions can be divided into two main types: physical reactions and chemical reactions. Learning about these is important because they help us understand how science works.
Physical reactions are changes that happen to the appearance or state of a substance without changing what it is made of. For example, if you tear a piece of paper, it’s still paper. Or when an ice cube melts into water, it’s still water, just in a different form.
Chemical reactions are different because they create new substances. This happens when the molecules of the original materials change. Examples include burning a matchstick, rusting iron, or fireworks exploding. In these cases, the original materials turn into something completely new.
Chemical reactions can also be grouped by how they use or release heat. These are called endothermic and exothermic reactions.
Exothermic reactions release heat into the surroundings. A good example is burning a matchstick, which gives off heat and light. This release of energy is what makes exothermic reactions special.
Endothermic reactions absorb heat from their surroundings. For instance, when water evaporates, it takes in heat, allowing it to turn into vapor. Photosynthesis is another example, where plants use sunlight to turn carbon dioxide and water into glucose and oxygen.
Knowing the difference between physical and chemical reactions, as well as understanding endothermic and exothermic processes, is important for anyone curious about science. These basic ideas help explain the world around us and are the building blocks for more advanced science topics. By watching the world closely, we can see the amazing reactions that shape our environment.
Experiment with Ice: Take an ice cube and place it in a bowl. Watch it melt and turn into water. Discuss with a friend or family member whether this is a physical or chemical reaction and why. Try freezing the water again to see if it turns back into ice. What does this tell you about physical reactions?
Colorful Chemical Change: With the help of an adult, mix baking soda and vinegar in a clear cup. Observe the fizzing and bubbling. Discuss what new substances might be forming. Is this a physical or chemical reaction? Why do you think so?
Heat Detective: Go on a “heat detective” mission around your home. Look for examples of exothermic and endothermic reactions. For instance, feel the warmth of a candle flame (exothermic) or notice how your skin feels cooler when you apply rubbing alcohol (endothermic). Share your findings with your class or family.
