Science Activity: Split (Yes, Split) Milk

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Do you think there's a mistake in the title of this activity? Do you think the word split has accidentally been substituted for spilled? If you do, you're wrong! This activity will show you how to take ordinary milk and break it apart.

1. Get Ready

1/2 cup skim or lowfat milk
4 tablespoons white vinegar
Two glasses
Spoon
Coffee filter and funnel

2. Do and Wonder

Put the milk in one glass and the vinegar in the other.

In a minute, you're going to slowly pour the vinegar into the milk. What do you predict will happen?

Add the vinegar to the milk by slowly pouring it down the inside of the glass. Observe what's happening at the surface of the milk by looking through the side of the glass.

Next you're going to stir the liquid. What do you predict will happen?

After 5 minutes, stir the liquid using the spoon. What do you observe?

Pour the liquid through the coffee filter, and observe how the parts separate.

3. Think and Write

If you left ordinary milk in a warm area for a day or two, it would get sour. You wouldn't need to add anything to it. Knowing this, what would you guess to be one of the substances produced when the bacteria in milk consume the natural sugars found in it?

Explanation

By adding vinegar to the milk, you made instant sour milk? The vinegar is a weak acid that causes a change in the proteins that are part of the liquid. They start to stick together, forming a solid. The solid is called curd, and the liquid is called whey.