Physical and Chemical Changes

Kate and Nicolette

What is a Physical Change?

A Physical Change is a visible, generally reversible change of the physical state of matter

What is a Chemical Change?

A Chemical Change is the result of a reaction which creates one of more substances with different chemical properties

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CHEMICAL CHANGE CHEAT SHEET:

not all chemical changes are explosive, here are some ways to know if a chemical change has occurred:


- gas formed (bubbles, fizzing)

-Precipitant formed (solid by combination of 2 liquids)

-Production of energy (light, sound, heat, movement)

-Smells, produces an odor change

-UNEXPECTED Change in color

Do it on your own!

Below are two different easy at home recipes; one of a cake and one of ice cream. Even if you don't actually do these, take a minute to go through the steps and think about whether or not each of them have physical or chemical changes.

Physical Change Ice Cream recipe


Ice cubes (enough to fill about half of a gallon sized bag)

1 cup half and half

1/2 cup salt (Kosher or rock salt works best, but table salt is fine)

2 tablespoons sugar

1/2 teaspoon vanilla extract

1 pint-size ziplock bag

1 gallon-size ziplock bag

Combine the sugar, half and half, and vanilla extract in the pint-size bag and seal it tightly.

Place the salt and ice in the gallon-size bag, then place the sealed smaller bag inside as well. Seal the larger bag. Now shake the bags until the mixture hardens (about 5 minutes). Feel the small bag to determine when it's done.

Take the smaller bag out of the larger one and eat the ice cream right out of the bag.

Chemical Change Cake Recipe

1 1/2 cups of sifted cake flour

1 1/2 teaspoons of baking powder

1/4 teaspoon of salt

1/2 cup, or one stick, of unsalted butter (softened)

1 cup of sugar

2 large eggs (room temperature)

1/2 teaspoon of vanilla extract

1/2 cup of whole milk

Heat the oven to 400 degrees F., lightly coat an 8-inch cake pan with butter and dust with all-purpose flour.

Sift the cake flour, baking powder, and salt into a large mixing bowl.

Beat in the butter 1/4 teaspoonful at a time, using an electric mixer set on low speed, until the mixture resembles coarse sand.

Beat in the sugar a tablespoon at a time, until the mixture resembles fine damp sand.

Beat in the eggs one at a time.

Add the vanilla and milk, and beat on medium-high, just until blended. Do not overbeat.

Pour into the prepared pan and bake until a toothpick can be inserted in the center and come out clean — 30 to 35 minutes.

Cool cake in the pan on a wire rack for 5 minutes.

If you did that, you probably came to the conclusion that making ice cream does contain any of the indicated "cheats" from the chemical change cheat sheet, so it only has physical changes. This is not true when baking a cake because you find many of the "cheats" present.