1. Chapter 2 Matter and Change . 2.2 Mixtures 2.1 Properties of Matter
2.3 Elements and Compounds
2.4 Chemical Reactions
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2. How can mixtures be classified?
Classifying Mixtures
Describing Matter
How can mixtures be classified?
A mixture is a physical blend of two or more components.
Based on the distribution of their components, mixtures can be classified as heterogeneous mixtures or homogeneous mixtures.
A mixture in which the composition is not uniform throughout is a heterogeneous mixture. Example mixing water and oil.
A homogeneous mixture is a mixture in which the composition is uniform throughout. Examples oil and vinegar.
Another name for a homogeneous mixture is a solution.
Many solutions are liquids. But some are gases, like air. And some are solids, like stainless steel, which is a mixture of iron, chromium, and nickel.
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3. Describing Matter
The term phase is used to describe any part of a sample with uniform composition and properties.
By definition, a homogeneous mixture consists of a single phase.
A heterogeneous mixture consists of two or more phases.
When oil and vinegar are mixed, they form a heterogeneous mixture with two layers, or phases.
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4. At the beach, you realize that both ocean water and sand are mixtures
At the beach, you realize that both ocean water and sand are mixtures. Which is a homogeneous mixture (or solution)? Which is a heterogeneous mixture?
Salt water is a homogeneous mixture, or solution. Sand is a heterogeneous mixture.
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5. How can mixtures be separated?
Separating Mixtures
Separating Mixtures
How can mixtures be separated?
To separate a mixture of olive oil and vinegar, for example, you could decant, or pour off, the oil layer.
Or, you might cool the mixture until the oil turned solid.
Pouring off the oil layer takes advantage of the fact that oil floats on water.
Cooling until the oil layer turns solid takes advantage of a difference in the temperatures at which the olive oil and vinegar freeze.
Differences in physical properties can be used to separate mixtures.
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6. Separating Mixtures
Filtration
The process that separates a solid from a liquid in a heterogeneous mixture is called filtration. Separate base on particle size.
Filter paper used in a laboratory is similar to coffee filters.
Filter paper is often placed in a funnel.
Then the mixture is poured into the funnel.
Solid particles that cannot pass through the filter remain in the funnel.
The rest of the particles pass through.
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7. Distillation Separating Mixtures .
During a distillation, a liquid is boiled to produce a vapor that is then condensed into a liquid. Separate base on differences in boiling point.
The figure below shows an apparatus used to perform a small-scale distillation.
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8. Distillation Separating Mixtures
As water in the distillation flask is heated, water vapor forms, rises in the flask, and passes into a glass tube in the condenser.
The tube is surrounded by cold water, which cools the vapor to a temperature at which it turns back into a liquid.
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9. Distillation Separating Mixtures
As water in the distillation flask is heated, water vapor forms, rises in the flask, and passes into a glass tube in the condenser.
The tube is surrounded by cold water, which cools the vapor to a temperature at which it turns back into a liquid.
The liquid water is collected in a second flask.
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10. Distillation Separating Mixtures
The solid substances that were dissolved in the water remain in the distillation flask.
This is because their boiling points are much higher than the boiling point of water.
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11. Which physical property does filtration rely on to separate mixtures
Which physical property does filtration rely on to separate mixtures? Which does distillation rely on?
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12. Which physical property does filtration rely on to separate mixtures
Which physical property does filtration rely on to separate mixtures? Which does distillation rely on?
Filtration relies on the size of a particle, or molecule, of a substance. Distillation relies on the boiling point of the substance.
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13. Differences in physical properties can be used to separate mixtures.
Key Concepts
Mixtures can be classified as heterogeneous mixtures or as homogeneous mixtures, based on the distribution of their components.
Differences in physical properties can be used to separate mixtures.
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14. Glossary Terms
mixture: a physical blend of two or more substances that are not chemically combined
heterogeneous mixture: a mixture that is not uniform in composition; components are not evenly distributed throughout the mixture
homogeneous mixture: a mixture that is uniform in composition; components are evenly distributed and not easily distinguished
solution: a homogeneous mixture; consists of solutes dissolved in a solvent
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15. phase: any part of a sample with uniform composition and properties
Glossary Terms
phase: any part of a sample with uniform composition and properties
filtration: a process that separates a solid from the liquid in a heterogeneous mixture
distillation: a process used to separate components of a mixture using differences in boiling points
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16. END OF 2.2
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