Elements, Compounds, Mixtures

​Element

• Consist of one type of atom​

• Can have multiple atoms but MUST all be the same type​

• Are pure substances​

• Are found on the periodic table​

  • Can be identified by a chemical symbol

​Compound

• Are two or more different elements chemically bonded​

  • elements are bonded in a fixed ratio ​

  • for example, all water is 2 hydrogens and 1 oxygen​

• Only a chemical reaction can pull apart​

• Can be identified by a chemical formula​

  • the chemical formula for water is H₂O

​Mixture

• Two or more different elements NOT chemically combined​

• Two or more compounds not chemically combined​

• Can also be a mixture of elements and compounds ​

• Can be separated manually, without a chemical reaction

​Separating Mixtures

Next week we will brainstorm ideas for separating a mixture.​

Let's review some common techniques.

​You may have used some of these techniques yourself.​​

Maybe you picked the marshmallows out of your favorite cereal to eat them first.​​

​Or sieving sand to collect small shells.

​Separating Mixtures

1. separating by picking out with your hand = hand picking​

   • Example: I only like red M&Ms, so I handpicked all of the red candies.

2. separating by shaking or hitting (done commonly with wheat) = threshing​

3. separating by blowing air through = winnowing​

4. using a colander, strainer, or sieve to pull out larger items = sieving​

5. allowing the liquid to become a gas leaving behind a substance = evaporation​

   • Example: I dissolved sugar in water to make a solution. I can separate the two by using heat to evaporate the liquid water, and leave the sugar behind.

6. first evaporation then collecting the liquid = distillation​

7. letting more dense items sink = sedimentation​

8. using a funnel to separate two liquids with different densities = separating funnel​

9. removing a magnetic material using a magnet = magnetic separation

10. using a filter = filtration​

• Example: I got coffee grinds in my cup of coffee. I used a filter to remove the grinds and separate them from my drink.

​Check for Understanding

Can you answer the following questions? ​

• What is an element? An example of an element? ​

• What is a compound? An example of a compound?​

• What is a mixture? An example of a mixture?​

• Can you give 3 examples of mixtures, and how you could separate them?

Multiple Choice

A substance made of two or more PHYSICALLY combined substances is--

• an element

• a mixture

• a compound

Multiple Choice

Which one of the following would you use to separate sand from iron filings?

• magnet

• filter paper
• threshing

• evaporation

Multiple Choice

Contains two or more atoms chemically combined

• Elements
• Compounds
• Mixtures

Multiple Choice

This picture represents which of the following?

• element
• compound
• mixture of elements

• mixture of compounds

Multiple Choice

Contains only one kind of atom.

• Element
• Compund
• Mixture

Multiple Choice

Is sugar (C₁₂H₂₂O₁₁) an element or a compound?

• Element
• Compound

Multiple Choice

This picture represents which of the following?

• element
• compound
• mixture