What you will need:
- Glass jar
- Lemon Juice
Milk is a colloid, meaning it is a substance that does not separate easily, because it is made of very tiny particles. What we've done is "curdled" the milk, or made it go bad. The acid from the lemon juice lowers the pH of the milk. This causes the casein particles (what the milk is made of) to come out as solid chunks of milk. The chunks are small, because they do not like being touched by the acid in the lemon juice, but they become big enough so you can see them!
You can try this experiment with other acids you might have in your house, vinegar, orange juice, or even lime juice. You will also find that you try this experiment you will have different results, cold milk out of the fridge, milk at room temperature, milk heated up. Have fun but remember: Do NOT drink the milk when you are finished with this experiment!
So in most cooking when the mixture curdles we say it's gone bad but it's not always the case as you need to curdle the milk to make cheese. So here's something else you can try, click this link to take you to the instructions: