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2.  This slide show covers the following course outcomes (refer to your “Outcomes” handout for Unit 3): › 3.1 › 3.2 › 3.3 › 3.4 › 3.5 2

3.  Complete the KWL chart below about pure substances and mixtures. K What you already know W What you wonder about L What you learned 3

4.  A pure substance is matter that is the same throughout.  According to the Particle Theory of Matter (PTM): › All matter is made up of tiny particles. › The particles of one substance differ from the particles of other substances.  What does this mean for pure substances ? › We can infer that the particles in a pure substance are identical while the particles in a mixture are different. 4

5.  To consider pure substances, let’s consider our most important chemical: water. › Most of you should recognize the chemical symbol H 2 O. What does this mean? › The symbol H 2 O refers to the parts of a water particle: 2 parts hydrogen (H) to 1 part oxygen (O). › So, if water contains hydrogen and oxygen, why is it considered a pure substance?? 5

6.  The fact that water is a pure substance stems from the definition. That is, it is a substance that is the same throughout. › Q: If you took 10 drops of clear water and looked at each drop under a microscope, what would you notice? › A: Each drop is exactly the same ! (Fig.7.5) › Every water particle is identical – each particle contains 2 parts hydrogen and 1 part oxygen. 6

7.  Now, consider tap water. › Q: How would a drop of tap water compare with a drop of pure water? › A: The drop of tap water would contain water particles (H 2 O) but would also contain different particles such as chlorine, salt, dirt, etc. › Since there is more than one type of particle, tap water is a mixture (see figure 7.7, p.237) 7

8.  A pure substance is matter that is the same throughout. › Every particle in the substance is identical. › Examples: pure water, oxygen, carbon dioxide  A mixture is matter that contains more than one type of particle. › Examples: tap water, air, soup 8

9.  Read pages 236-237.  Complete the “Reading Check” (#1-3) on page 237.  Complete the “L” column in the KWL chart to explain what you learned and to answer your “wondering” questions.  Research Question: › There are two types of pure substances: elements and compounds. Define these terms and find a few common examples of each. 9