Elements, Compounds and Mixtures

Pure Substances:Elements and Compounds

Matter

CompoundElement

Pure Substance

Heterogeneous Mixture

Homogeneous Mixture

Mixture

• Substance made of one material and has definite properties

• Particles of a substance are all alike

• Same throughout

Pure Substance

• Simplest form of a pure substance

• Cannot be changed into a simpler substance by any chemical process

• Found on periodic table

CompoundElements

Pure Substance

• Atom– Smallest particle of an element– Basic building block of matter

CompoundElements

Pure Substance

• Pure substances made of more than one element

• 2 or more elements chemically combined

CompoundElement

Pure Substance

Sodium: extremely explosive when it comes in contact with water

Chlorine: a poisonous gas

Two Elements

Combine to form…

… Sodium Chloride

We put it on our french fries!

• Compounds are made of molecules

• Molecule: two or more atoms bonded together

Every water molecule is exactly the same

2 Hydrogens bonded to 1 Oxygen

CompoundElement

Pure Substance

Compounds … continued

• Not always 2 different atoms bonded together

• Oxygen = element

• Oxygen that we breathe is a molecule– O2

Mixture

• Matter that consists of two or more substances mixed together, but NOT chemically combined

• Substances that make up a mixture can be present in varying quantities

• Can be separated by physical means• Methods used to separate a mixture are based

on the properties of its components

Types of Mixtures

Heterogeneous Mixture

• A mixture that does NOT appear to be the same throughout

• “least mixed” of all mixtures

Homogeneous Mixtures

• A mixture that appears to be the same throughout

• “Well mixed” mixture

• Does NOT separate upon standing

Colloid

• A homogeneous-looking mixture in which the particles are mixed together, but NOT dissolved

• Has some characteristics of homogeneous mixtures (particles are evenly spread throughout) and some characteristics of heterogeneous mixtures (particles are not actually dissolved)

Colloid (refer to fig 4-9 on p. 92)

• Actually falls somewhere between a solution (homogeneous mixture) and a suspension (heterogeneous mixture)

• Particles are kept permanently suspended• Particles are relatively large• Will NOT separate upon standing• Examples: mayonnaise, toothpaste, milk,

fog

Alloys

• Homogeneous solutions of metals

• Solid Solution

• Often used in jewelry

• Example – brass: alloy of copper and zinc, Gold jewelry is an alloy of gold and copper

Solution

• Homogeneous mixture of two or more substances

• “best mixed” mixture

• Composed of solute and solvent

Solute

• Substance that is dissolved

• Substance that there is less of– Example: salt is the solute in salt water solution

Solvent

• Substance that does the dissolving

• Substance that there is more of– Example: water is the solvent in salt water

solution

• Since water is used as the solvent most often, it is called the “universal solvent”

Characteristics of a Solution

• Composed of a solvent and solute

• Particles are NOT large enough to be seen

• Does NOT scatter light

• Properties are evenly spread out (for example: color, taste, odor, etc.)

• Types of solutions: Fig. 4-12, p. 94

Properties of Elements, Compounds and Mixtures

Elements Compounds Mixtures

Made up of only one kind of atom

Made up for more than one atom

Made up of more than one kind of

moleculeCannot be

broken down by chemical means

Can be broken down by chemical

means

Can be separated by physical means

Has the same properties as the atoms making it

up

Has different properties from the elements making it

up

Has same properties as the

substances making it up

Has the same properties throughout

Has the same properties throughout

Has different properties throughout

Identify the following with as many terms as apply:

1. Table Salt

2. Brass

3. Iron

4. Trail Mix

5. Gold

6. Water

7. Sugar

8. Mayonnaise

9. Fog

10. Tacos

Homogeneous Mixture

Element

Heterogeneous Mixture

Compound

Colloid

Alloy

Solution

Answers1. Table Salt – compound

2. Brass – homogeneous mixture, alloy

3. Iron – element

4. Trail Mix – heterogeneous mixture

5. Gold – element

6. Water – compound

7. Sugar – compound

8. Mayonnaise – homogeneous mixture, colloid

9. Fog – homogeneous mixture, colloid

10. Tacos – heterogeneous mixture