1. UNIT: Matter Objectives: Lesson 3 of 4 You will understand the difference between an element and a compound You will learn how bonds form between atoms You will learn the difference between a molecule and a compound You will understand the difference between heterogeneous and homogeneous mixtures TOPIC: Elements, Compounds & Mixtures

2. Quickwrite In 1-2 sentences answer one of the questions below: What do you think the difference is between an element and a compound? When you drink water, do you think it mostly made up of one type of element or a combination of elements? If you drink a sports drink such as Gatorade, do you think it mostly made up of one type of molecule or mixture of molecules?

3. Elements All elements can be found on the periodic table Elements are substances made of only one type of atom They are the simplest forms of matter Elements cannot be broken down into simpler substances Elements cannot be physically separated For example, pure Gold contains only Gold atoms Pure Carbon (graphite) contains only Carbon atoms

4. Elements Helium Balloon = He Have you ever inhaled helium to alter voice? If so, you inhaled a pure substances made of only one type of atom In other words, you inhaled Helium as a pure element

5. What is an Element? Substances made of only one type of atom They are the simplest forms of matter and cannot be broken down into simpler substances Example: Gold (Au), Carbon (C)

6. + - + - Bonds Between Atoms A chemical bond is when two atoms share or transfer electrons Consider the two hydrogen atoms below When two hydrogen atoms get close enough, a bond may form The result is a molecule of hydrogen gas or H 2 Bond

7. Bonds Between Atoms - - - - - - - - - - - - - - - - - - - - Fluorine Atom Sodium Atom Bond Some bonds form when electrons are actually Transferred from one atom to the other For example when Sodium bonds with Fluorine to make Sodium Fluoride (NaF), the electron is completely removed from the sodium atom

8. What is a Chemical Bond? A chemical bond is when two atoms share or transfer electrons Example: molecule of H 2 or NaF + - + - Bond

9. Compounds A Compound is a pure substance made up of two or more elements that are bonded together For example, consider common table salt, sodium chloride Sodium (Na) Chloride (Cl) forms when the element sodium bonds with the element Chlorine; forming a new chemical compound Or, consider water Water forms when Hydrogen (H) bonds with Oxygen (O) 2

10. Molecules vs. Compounds A molecule is two or more atoms bonded together A compound is substance made up of two or more kinds of different elements that are bonded together So what is the difference between a molecule and compound? For example, Air is made up of oxygen O 2 and nitrogen N 2 molecules Because they are made up of only one kind element, they can only be molecules and NOT compounds Air Mixture = O 2 = N 2

11. Water = Water (H 2 O) A molecule is two or more atoms bonded together A compound is a substance made up of two or more kinds of different elements that are bonded together For example water (H 2 O) is a compound because it contains two elements: hydrogen and oxygen bonded together Water (H 2 O) is also a molecule because it is made of two or more atoms bonded together Because it meets both definitions, water (H 2 O) is both a molecule and a compound Therefore, all compounds are molecules, but not all molecules can be compounds Molecules vs. Compounds

12. What is the difference between a molecules and a compound? A molecule is two or more atoms bonded together, Example: O 2, O 3 and N 2 A compound is substance made up of two or more kinds of different elements that are bonded together Example: H 2 O

13. Chemical Formulas A chemical formula is used to represent a compound A chemical formula is a group of symbols that shows the number and kinds of atoms in a compound For example, in sodium chloride, or salt the chemical formula is NaCl By writing NaCl, this tells us the compound contains one sodium atom and is chemically bonded to one chlorine atom Let’s take a look at the chemical formula for water: H 2 O The chemical formula for water tells us that the compound contains two hydrogen atoms bonded to one oxygen atom 2

14. What is a chemical formula? Used to represent a compound, it is a group of symbols that shows the number and kinds of atoms in a molecule or compound Example: NaCl & H 2 O

15. Determine how many atoms of each element are in each compound below: CaCl 2 Answer: The above compound CaCl 2 contains one calcium atom and two chlorine atoms O 3 Answer: The above compound O 3 contains three oxygen atoms (NH 4 ) 2 S Answer: The above compound (NH 4 ) 2 S contains two nitrogen atoms atoms 2 x (1N) = 2N, 8 hydrogen atoms 2 x (4H) = 8H, and one sulfur atom 1 x (1S) = 1 S Practice:

16. Mixtures Most matter you see is a mixture A mixture is two or more substances mixed together Take salt and water for example If you were to mix these two compounds, Salt (NaCl) + Water (H 2 O) you would create a mixture The air you breathe is actually a mixture of mostly Oxygen gas (O 2 ) + Nitrogen gas (N 2 ) + and Argon Salt Water = O 2 = N 2 = Ar Air Mixture

17. What is a Mixture? One or more substances that are mixed together not bonded to one another Most types of matter are mixtures Ex: Salt + water (NaCl + H 2 O)

18. Air Mixture In a homogeneous mixture, the substances are evenly mixed Once again, consider the air we breathe Recall that Air is a mixture of mixture of mostly Oxygen gas (O 2 ) + Nitrogen gas (N 2 ) + and Argon These molecules/atoms are evenly mixed, every breathe you take is the same as the one before it The molecules and atoms are also far too small to be seen and therefore CANNOT be individually selected and “picked” out with your hand = O 2 = N 2 = Ar Homogeneous vs. Heterogeneous Mixture

19. Salt Water Mixture Consider another homogeneous mixture of salt and water Notice, the salt and water molecules throughout the mixture are evenly mixed If you were to drink the homogeneous mixture of salt water, every sip would most likely taste the same as the previous sip before it Just like in the last mixture, the atoms/molecules are far too small to be seen and therefore CANNOT be “picked” out In other words, you can’t individually pick out the salt atoms/molecules with your hand = Water (H 2 O) = Sodium (Na) = Chlorine (Cl) Homogeneous vs. Heterogeneous Mixture

20. A heterogeneous mixture is when one or more of the substances are NOT mixed evenly Often times, in a heterogeneous mixture, the objects are large enough to be seen and therefore CAN be picked out Consider a heterogeneous mixture of sand and water Notice, the molecules throughout the mixture are NOT evenly mixed The sand particles in the mixture are large enough to be seen and CAN be individually selected and “picked” out by hand = Sand (SiO 2 ) = Water (H 2 O) Water & Sand Mixture Homogeneous vs. Heterogeneous Mixture

21. Consider another heterogeneous mixture of Oil and Water (H 2 O) Notice, the molecules throughout the mixture are NOT evenly mixed That is, the oil molecules are not mixing with the water molecules If you were to drink this mixture, each sip would most likely taste different than the previous sip before it = Oil Molecule = Water (H 2 O) Oil & Water Mixture Homogeneous vs. Heterogeneous Mixture

22. What is the difference between a Homogeneous vs. Heterogeneous Mixture? Homogeneous mixtureHeterogeneous mixture Mixed evenlyMixed unevenly Substances cannot be seen or “picked out” Substances can sometimes be seen and “picked out” Ex: Salt + waterEx: Water + Sand

23. Summarize: (you can always write you own) Compare and contrast the following types of matter: element, compound and mixture Describe the components of an atom How many atoms are in the compound Al 2 O 3 Draw the flow chart seen to the right: