Chemical Change Affected by Heat _On grade _03
A chemical change is when a substance changes into another substance. Unlike a physical change, a chemical change cannot be easily changed back and only occurs with another chemical change. So how can you tell if a chemical change is taking place? Fortunately, there are some observable indicators of chemical changes. During a chemical change, you may observe a change in smell, taste, or color. You may even recognize that a gas is being released. Bubbles are often a sign that a gas is being released.

Chemical changes are actually very common in your daily life, you just need to know where to look. Remember that campfire on your last camping trip? You started with twigs and logs, and by the next morning, all that was left was ashes. The heat from the fire caused the chemical change to occur.
Heat speeds up chemical changes, which is why you place certain foods in the refrigerator. For example, fresh lettuce should be green and crunchy, but over time, the lettuce will turn brown and soft and will not look or taste as good. If it is not kept cool, it will decay more quickly.
Some people don’t throw their old decayed food in the garbage. Instead, they place it in their compost pile they have constructed in their backyard. A compost pile is a mound of decaying plant material. The pile of decaying material creates heat, and it is this heat that speeds up the decaying process. Over time, the material changes form and starts to look more like soil than rotten, old plants. This composted organic material can then be added to gardens as a fertilizer.

There sure are a lot of chemical changes, but out of all of them, making cookies is your favorite. Mix up some dough and add that magic ingredient, heat. That change in taste and smell makes them just right. Yumm!