Chapter 4 Elements, Compounds, &

Mixtures

Gold Salt Fields Granite

Elements

• Are pure substances that cannot be separated into simpler substances by physical or chemical changes.

• Elements are found on the periodic table of elements

Pure Substance

• Contains only one type of particle.

• Example: 5 grams of the element gold is like all other particles of gold.

• The particles of a pure substance are alike no matter where that substance is found.

Identifying Elements

• Physical properties and Chemical properties are ways in which you may identify an element.

• Examples of Physical Properties: melting point, density, color, hardness, and texture.

• Examples of Chemical Properties: flammability, reactivity with oxygen, acid & water.

Elements are Classified by their Properties

• Elements are divided into three categories: Metals, Nonmetals, & Metalloids.

• Elements are classified into groups according to their shared properties.

• Example: Iron, Nickel & Cobalt are all shiny and conduct electric current therefore scientists have grouped them into the metal section of the periodic table.

Metals

Are: – Shiny– Good conductors of thermal energy– Good conductors of electric current– Malleable (hammered into sheets)– Ductile (drawn into thin wires)

Examples: Copper, Lead, Tin

Copper

Nonmetals

• Are: – Dull– Poor conductors of thermal energy– Poor conductors of electric current– Brittle– Unmalleable

Examples: Sulfur, Bromine, Neon

Sulfur

Metalloids

• Are: – Have both properties of metals & nonmetals– Some are shiny some are dull– Somewhat Malleable and ductile– Some conduct thermal energy and electric

current well

Examples: Silicon, Antimony, Boron

Silicon

Compounds

• A pure substance composed of two or more elements that are chemically combined.

• In order for elements to combine they must react or undergo a chemical change with another.

• Examples: Table salt- sodium and chlorine Water- hydrogen and oxygen

• Once the chemical change occurs you have another pure substance

• http://www.youtube.com/watch?v=0evGDGkOMvc

Compounds…

• Each compound like elements has its own unique set of physical and chemical properties that helps you identify it.

• Example:

-boiling point

-melting point

-density

-color

-reactivity

Compounds in Nature

• Proteins are compounds found in all living things.

• Nitrogen is needed to make proteins.

• Plants get their nitrogen compounds from the soil. Animals get the nitrogen they need by eating plants or animals that have eaten plants.

Quiz 1. An element is a pure substance that cannot be _________ into other

substances. A. combined C. madeB. separated D. burned

2. Which two categories of elements are good conductors of electricity? A. Metals and Nonmentals c. Metals and some MetalloidsB. Nonmetals and Metalloids d. Water and Metals

3. Elements are divided into three categoriesA. metals, nonmetals, metalloidsB. metals, solids, liquidsC. solids, liquids, gassesD. cobalt, iron, nickel

Quiz Continued

4. Two or more elements that are chemically combined are called___________.

A. metals C. pure substanceB. elements D. compounds

5. True or False In order for elements to combine they must react or undergo a chemical change with another.

Mixtures

• Are a combination of two or more substances that are not chemically combined.

• Two or more materials together form a mixture if they do not react to form a compound.

Example: A Pizza: dough, sauce, pepperoni, cheese, olives. They do not react when put together.

Mixtures continued…

• Since no chemical change has occurred the substance still has the same chemical makeup it had before it was combined with the other substances.

• Mixtures can be physically separated. If you don’t like olives on your pizza you may pick them off. This is a physical change of the pizza.

Mixtures Continued…

• Mixtures are not all as easy to separate. Salt water can be separated but you must separate the salt from the water by heating the mixture. The water changes from a liquid to a gas, and the salt remains.

• Other ways to separate mixtures: - Distillation is a process that separates a mixture based on its boiling point. (saltwater)-Centrifuge separates according to the densities of the components. (blood)-Magnet can separate iron from aluminum.

Mixtures vs. Compounds

Mixtures

1. Are elements, compounds, or both.

2. Separated by physical means.

3. They keep original properties.

Compounds

1. Are elements.

2. Lose their original properties.

3. Separated by chemical means.

Solutions

• A mixture that appears to be a single substance but is composed of particles of two or more substances that are distributed evenly amongst each other.

• Example: Saltwater

Nerdy Science Joke of the day

• What did the compound say to the solution?

• Answer: You’re all mixed up!

Solute vs. Solvent

• In solutions the Solute is the substance that is dissolved.

• The Solvent is the substance in which the solute is dissolved.

• Example: In saltwater salt is the solute or the substance that is dissolved. While water is the solvent which dissolves the salt.

Solubility

• Is the amount of solute needed to make a saturated solution.

• If a solution contains all the solute it can hold at a given temperature it is saturated. An unsaturated solution contains less solute than it can hold at a given temperature.

• Mixing, Heating & Crushing all affect how quickly solids will dissolve in liquids.

http://www.youtube.com/watch?v=3G472AA3SEs

Suspensions

• Are mixtures that have particles of a material throughout it. They settle to the bottom but do not dissolve.

• Example: When you shake a snow globe, the snow moves around but eventually falls to the bottom.

Nerdy Science Joke Alert!

• “Settle Down!”

• What did the chemist say to the suspension?

Colloids

• Are mixtures in which

particles are dispersed

throughout but are not heavy enough to settle to the bottom. The particles are small and fairly well mixed.

• Example: Jello is an example of a colloid.

Quiz

1. A mixture is a combination of ______ substance(s) that are not ______ combined.

A. one, chemically C. two, chemically B. two, physically D. one, physically

2. True or FalseMixtures can be physically separated.

3. The __________ is the substance that is dissolved, and the _________is the substance that dissolves.

A. water, salt C. solvent, soluteB. solute, solvent D. solution, water

Quiz

4. Solubility is how much __________ can be dissolved. A. metal C. gasB. water D. solute

5. A snow globe is an example of a ______. A. colloid C. solventB. suspension D. compound

6. A ________is a fairly well mixed mixture which the particles are not heavy enough to settle out.

A. suspension C. solutionB. colloid D. ratio