Chapter 3 Elements, Compounds, and Mixtures

Think About It?  Can all substances or objects be “broken down”? Explain your answer.

An element is…  A pure substance that cannot be broken down by physical or chemical means.

A pure substance is…  A substance that is made of only one kind of particle

Which of these is a PURE SUBSTANCE?

A characteristic property…  Can identify a substance  DO NOT depend on the amount of the substance

Examples of Characteristic Properties…  Boiling Point  Melting Point  Density  Reactivity with acid

Look at the characteristic properties. How are these substances different?

Metal, Nonmetal or Metalloid?  All elements can be separated into these 3 major categories  How do we put all objects into these main groups?

Metals  Shiny  Can conduct heat and electricity  They can be formed into sheets and wire  Examples: tin, gold, copper

Nonmetals  Dull (non-shiny)  POOR conductors of heat and electricity  Solids are brittle (break easily)  Examples: iodine, sulfur, neon

Metalloids  These can have properties of BOTH metals and nonmetals

Homework  Page 59  #1,2,3,5,6,7

Section 2 - Compounds

What do water, baking soda, sugar and salt all have in common?  Even though many of these substances have different properties, they are all made of certain elements.  These elements CHEMICALLY combine to form new substances  Example: hydrogen + oxygen = water  Sodium + Chlorine = Salt  These new substances are called compounds

What is a compound?  A compound is a pure substance composed of TWO or more elements that are CHEMICALLY combined.  A particle of a compound is called a molecule

Examples of Compounds

Fill out the following table, use page 60 in your textbook CompoundElements Combined Table SaltSodium + Chlorine WaterHydrogen + Oxygen Vinegar Hydrogen + Carbon + Oxygen Carbon DioxideCarbon + Oxygen Baking SodaSodium + Hydrogen + Carbon + Oxygen

Properties of Compounds  Most of the time a compound has very different properties compared to the elements that make that compound.  Salt is a really good example of this…

Breaking Down Compounds  Breaking down compounds can be difficult.  Two ways to break down a compound:  Apply heat  Apply and electric current

In IndustryIn Nature Where do we find compounds?  Aluminum is created by breaking down aluminum oxide (AL + O)  Ammonia (N + H) is used in fertilizers  Nitrogen compound such as proteins are needed for all living things  Carbon Dioxide (C+O) is a crucial part of photosynthesis and respiration

Homework  Page 63 #1-6

How do compounds form?  Take a look at this water molecule. It has ONE oxygen atom and TWO Hydrogen atoms. Water ALWAYS looks that way no matter what, but why? Why not just one hydrogen atom, why not three?

It’s all about the electrons!  Atoms love to give, take and share electrons. When two or more elements do that, a compound is formed.  The number of electrons is usually equal to the number of protons.

Electron Shells  Electrons like to hang out in groups  TWO electrons always hang out by the nucleus  Every other shell is a group of EIGHT electrons

It works out perfect for Argon…

…but Aluminum feels a little empty

Atoms want to feel COMPLETE…  That’s why atoms give each other electrons, or share the ones they have.

Section 3 Mixtures

What is a mixture?  A mixture is combination of substances that are PHYSICALLY combined  When substances are mixed they DO NOT create a new substance

Examples of Mixtures

Not All Mixtures Look The Same  Sometimes you can see the different parts of the mixture (like a salad)  But other times it is hard to see the different parts  A SOLUTION is a mixture where you cannot easily see the different parts of a mixture  Like This 

Solutes and Solvents  Solutions are made of two parts SOLUTES or SOLVENTS  Solvents DO THE DISSOLVING like the water in saltwater  Solutes ARE THE ONES DISSOLVED like the salt in saltwater

Think about the Kool-Aid, which parts are the solutes, which are the solvents?  Solutes = Sugar and powder  Solvents = Water

Look on page 67, complete the following chart… StatesExamples Gas in GasDry air (oxygen in nitrogen) Gas in LiquidSoft Drink (carbon dioxide in water) Liquid in LiquidAntifreeze (alcohol in water) Solid in LiquidSalt Water (salt in water) Solid in SolidBrass (zinc in copper)

Concentration  Concentration is the amount of a substance in a solution  Which of these graduated cylinders has the highest concentration?

Solubility  Solubility is the ability for a substance to dissolve in another.  Some substances dissolve really easily, other do not.

How could you make something dissolve faster?  Heating  Stirring  Breaking

Homework  1) Create a T-Chart comparing compounds and mixtures. Have at least 5 ideas on each side.  2) Give three examples of solutions, for each solution, name the solute and the solvent  3) What is solubility? Name one substance that has a high solubility and one substance that has a low solubility.