Sea water, milk, muddy water and a glass of lemonade all look like one thing, but each is a mixture. In this course we sort mixtures into solutions, colloids and suspensions, and we learn to say how much of a substance is dissolved in a solution.
3 lessons, about 1 h 20 min3 simulations10 problems6 practice questionsPython in every lesson
Created by StemPy LabIn science, a pure substance is made of only one kind of matter, and its properties, such as the melting point, are fixed. A mixture has two or more pure substances, its constituents. They are not joined by a chemical change, they can be in any amount, and they can usually be separated by physical means. A homogeneous mixture has the same composition everywhere, and is called a solution, as salt in water, air or brass. A heterogeneous mixture has parts that differ from place to place, as sand in water. An alloy is a mixture of metals. A pure substance is an element or a compound.
A solution is a homogeneous mixture of a solute dissolved in a solvent. Its concentration can be given as mass by mass percentage, mass by volume percentage or volume by volume percentage. A solution that cannot dissolve more solute at a given temperature is saturated.
A suspension has particles that can be seen, that settle and that can be filtered. A colloid has particles that are too small to be seen or to settle, but large enough to scatter light, which is the Tyndall effect.
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