A mixture is what you get when you combine two or more different things together, but each ingredient keeps its own properties and can be separated again. When you toss a salad, mixing lettuce, tomatoes, and cucumbers, you create a mixture: each vegetable stays distinct, and you could pick them apart if you wanted to. Trail mix combines nuts, raisins, and chocolate chips into one snack, but each piece remains separate and recognizable.

Mixtures appear everywhere in daily life. The air you breathe is a mixture of gases, mainly nitrogen and oxygen. Ocean water is a mixture of water and salt. Even concrete is a mixture of cement, sand, gravel, and water.

Scientists distinguish mixtures from compounds, where ingredients combine chemically and can't be easily separated. Water (H₂O) is a compound: hydrogen and oxygen bond together and lose their original properties. But saltwater is a mixture: the salt and water retain their characteristics, and you could separate them by letting the water evaporate.

Some mixtures look uniform throughout, like saltwater, while others show their different parts clearly, like a salad. When you're baking and the recipe calls for mixing flour, sugar, and baking soda, you're creating a mixture.