Mixtures vs Pure Substances

What are these pictures of?

How does this differ from the previous slide?

Compare and Contrast between the following

substances.

What do you see in this picture?

How are A and B similar?

How are C and D similar?

What makes A and C different?

Pure Substance

• Pure Substance is a form of matter that has a uniform and unchanging composition.

Water is a pure substance.

Oxygen is a pure substance

Which of the following is a pure substance?

• Sugar

• Pizza

• Air

Mixture

• A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties.

Air is a mixture because it contains hydrogen, oxygen, nitrogen, carbon dioxide and

impurities.

Which of the following are mixtures?

• Salt

• Salt-water solution

• Sugar

• Pizza

• Tap water

Heterogeneous mixture

• Heterogeneous mixture: is a mixture that does not blend smoothly throughout and in which the individual substances remain distinct.

The Earth is a heterogeneous mixture

Homogeneous mixture

• Homogeneous mixture: is a mixture that has constant composition throughout.

Salt-water is a homogenous mixture.

Which of the following is an example of a homogenous mixture? Heterogeneous

mixture?• Orange juice

• Gatorade

• Tomato juice

• Trail mix

• Dirty water

• Sugar-water

Solutions

• Solution: another name for homogenous mixture

When salt dissolves in water, it becomes a salt

water solution

What is another example of a solution?

filtration

• Filtration: is a technique that uses a porous barrier to separate a solid from a liquid.

Heterogeneous mixtures composed of solids and liquids are easily

separated by filtration.

Distillation

• Distillation is a separation technique that is based on differences in the boiling points of the substances involved.

Most homogenous mixtures can be separated by distillation.

Crystallization

• Crystallization: is a separation technique that results in the formation of pure solid particles of a substance from a solution containing the dissolved substance.

Making cock candy from a sugar solution is an example of

separation by crystallization.

Sublimation

• Sublimation: is the process during which a solid changes to vapor without melting.

When dry ice evaporates it goes through sublimation.

Chromatography

• Chromatography: is a technique that separates the components of a mixture based on the ability of each component to travel or be drawn across the surface of another material.

Forensic scientists can use ink chromatography to determine what type of marker was used at a crime

scene.

What separation technique would you use to separate foul water?

What separation technique would you use to separate salt water?