Physical and chemical changes in the kitchen (2023)

Moushumi Nath

April 09, 2020

How do you go from flour, sugar and eggs to cookies? Or from fruit juice to popsicles? Making food is all about change! these might bephysicistchanges orchemicalchanges.

Physical changes

A physical change is a change inState of matter. There are three main states of matter: solid, liquid, and gas.

If you freeze fruit juice to make a popsicle, that's a state change. The juice changes from liquid to solid. Melting ice cream on a hot day is also a state change. The ice cream changes from solid to liquid. Juice and ice cream are still juice and ice cream, even when they go from one state of matter to another.

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Sometimes when you cook a liquid it turns solid, like when a raw egg becomes a scrambled egg. This is not a status change. Status changes can usually be reversed. You can't turn scrambled eggs into raw eggs!

If you break something big into smaller pieces, that too is a physical change. When you grate a piece of cheese on your pizza, you are changing the block of cheese. Cheese is still cheese, even though the chunks don't look like the block of cheese you started with.

Sometimes the physical changes are hard to see. If you put a little sugar in the water and stir it, soon you won't be able to see the sugar. It didn't disappear! The sugar has just been broken into pieces too small to see.

It's like mixing red candies into a big bag of blue candies. The red candies can be hard to see, but they are still there.

chemical changes

Achemical changeit is a change in what something is done. We can tell that a chemical change has taken place by looking for certain clues.

One clue is the gas. The gas is produced during a chemical transformation. The next time you bake a cake or flip a pancake, look for the bubbles. Inside each bubble is a bit of gas. This gas is produced when the ingredients change each other.

The bubbles help make the food you bake fluffy. If you cut into a cake, you can see the spaces where there were gas bubbles in the wet dough.

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Not all blisters come from chemical changes. When mixing the dough with a whisk, you can see bubbles. These are just the air that gets trapped in the dough during the churning.

Speaking of gas... Smell is the second clue that a chemical change is taking place. Sour milk, rotten bananas, and moldy cheese all produce odors. These odors alert us not to eat that food. Food in poor condition or with mold can make us sick.

But there are plenty of smelly foods that are perfectly safe to eat!Blue cheesemiDurian fruitthey have very strong odors. They won't hurt you unless you are allergic to them. Everyone has different tastes. Many people love foods with unique smells.

Did you know?

Some people say that Durian fruit smells like paint thinner and onion, with a hint of gym socks stink!

Can you think of pleasant smells that may come from the kitchen? The smell of baked bread or roast turkey are signs that chemical changes are taking place!

The third clue is a change.heart. Think of the perfect browning you can get when toasting marshmallows over a fire. Or that dark brown color when you accidentally burn it. oops!

When tomatoes change color from green to red, it means they are ready to eat. When bananas turn from yellow to black, it means that they are no longer good to eat.

The color change can be a tricky clue. Sometimes it's hard to tell if a color change is due to a physical or chemical change.

Imagine adding red food coloring to white frosting. You now have pink frosting. Do you think it is a physical or chemical change? Do you remember stirring the sugar into the water? Food coloring works the same way. The color just spreads through the coverage. It does not change the coverage itself. This is a physical change.

So how can you tell if a change is physical or chemical? ask yourself:

• Is the substance the same now as it was before the change? If it's the same, it's a physical change. If not, it's a chemical change.
• Was there any change in color or odor? Was a gas formed? If any of these things happened, it was a chemical change.
• Can the change be easily reversed? If so, it was a physical change.

Your kitchen can be an amazing laboratory to explore the world of chemistry!

Changes in materials

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