8th Grade T3L1 p.95-96

Mixtures and Solutions

Classifying Mixtures

3 Types of mixtures

The types of mixtures are defined by the sizes of their particles.

Colloid

Suspension

Solution

Colloid: heterogeneous mixture that contains small, undissolved particles that do not separate or settle out when left undisturbed

- The particles in a colloid are too small to be seen without a microscope, but they are large enough to scatter light, which is why they are not clear


- Colloids remain consistently mixed and do not separate, even if left undisturbed for a long time.


EXAMPLES: Paint, milk, fog, smoke

Colloid: heterogeneous mixture that contains small, undissolved particles that do not separate or settle out when left undisturbed

Fog is an example of a colloid.

The densely-packed water molecules prevent most of the light rays from passing through, causing them to scatter

This scatters the light and makes it difficult to see through.

Multiple Choice

Which of the following best describes a colloid?

• A homogeneous mixture with small, dissolved particles that settle out when left undisturbed.

• A heterogeneous mixture with small, undissolved particles that separate when left undisturbed.

• A homogeneous mixture with large, dissolved particles that do not separate when left undisturbed.

• A heterogeneous mixture with small, undissolved particles that do not separate when left undisturbed.

Multiple Choice

Which of the following is an example of a colloid?

• milk
• sugar
• salt
• water

Multiple Choice

Why are colloids not clear?

• Colloids are not clear because they contain larger particles that scatter light.
• Colloids are not clear because they contain smaller particles that scatter light.
• Colloids are not clear because they have a low refractive index.
• Colloids are not clear because they are transparent.

Suspension: Suspension is a type of mixture where particles can be seen and separated by settling or filtration.

- Suspensions form when a distinct, cloudier layer accumulates at the top or bottom of a liquid while the rest becomes clearer.

- Suspensions can be easily separated into their constituent parts if left undisturbed.

- Filtration and settling are common methods used to separate the particles in a suspension.

Suspension: Suspension is a type of mixture where particles can be seen and separated by settling or filtration.

- Examples of suspensions include oil-and-vinegar salad dressing and muddy river water.

Multiple Choice

What is suspension?

• A type of mixture where particles cannot be seen and separated by settling or filtration.

• A type of mixture where particles can be seen and separated by settling or filtration.

• A type of mixture where particles are dissolved and cannot be separated.

• A type of mixture where particles are suspended in the air

Multiple Choice

Which of the following is an example of a suspension?

• Muddy water
• Saltwater
• Distilled water
• Tap water

Multiple Choice

What are common methods used to separate the particles in a suspension?

• Heating and cooling

• Evaporation and condensation

• Filtration and settling

• Dissolving and precipitating

Solution: A solution is a homogenous mixture consisting of a solvent and one or more solutes.

- The solvent, which is usually present in the largest amount, dissolves the other substances in the solution.

- The solute is the substance that is dissolved by the solvent

- Solutions can be solid, liquid, or gas

Examples: grape juice, air, stainless steal

Multiple Choice

What is a solution?

• A mixture of two or more solutes

• A mixture of a solvent and a solute

• A pure substance

• A mixture of gases

Multiple Choice

What is the role of the solute in a solution?

• It dissolves the solvent

• It surrounds the solvent particles

• It is dissolved by the solvent

• It forms a homogenous mixture

Multiple Choice

Which of the following is an example of a solution?

• Pure water

• Salt crystals

• Oil and water mixture

• A mixture of gases

Molecular Solutes: compounds that break up into individual molecules in water.

- The sugar molecules are polar (+/-) like water and are attracted to water molecules.

- The sugar molecules move away from each other due to the attraction with water molecules.

- The chemical bonds of the sugar molecules do not break when surrounded by water molecules.

- Nonpolar molecules are generally not soluble in water due to the importance of polarity in the dissolving process.

Ionic Solutes: ionic compounds are made of ions or particles that have a positive(+) or negative (-) charge.

- Table salt is an ionic compound composed of sodium chloride (NaCl) and is soluble in water.
- Sodium chloride is made up of positively charged sodium ions and negatively charged chloride ions.
- Water is a polar molecule with a slightly negative oxygen side and a slightly positive hydrogen side.
- The attractions between the positive and negative charges of sodium chloride and the polar water molecules allow salt to dissolve in water.

Multiple Choice

What is the nature of water molecules?

• Non-polar

• Ionic

• Covalent

• Polar

Multiple Choice

What enables salt to dissolve in water?

• Repulsion between the charges

• Magnetic attraction between the charges

• Gravitational force between the charges

• Attractions between positive and negative charges and polar water molecules

Categorize

Options (6)

milk

whipped cream

muddy water

salad dressing

lemonade

salt water

Organize these options into the right categories

Colloid

Suspension

Solution