Classifying Matter: Pure Substances and Mixtures

1. Bellwork • Q: Tap water is not just H2O. Guess 5 other things that are in the tap water (water that comes out of a faucet).

2. Section 1: Classifying Matter Vocabulary • Pure substance • Element • Atom • Compound • Heterogeneous mixture • Homogeneous mixture • Solution • Suspension • Colloid • Objectives • Understand the classification of matter • Distinguish between mixtures & pure substances • Define & distinguish between solutions, suspensions, & colloids

3. Classifying Matter • There are many classification systems we use. • We classify books & music based upon their genre. • We classify the safety of something based upon its ability to cause harm. • We classify friends based upon how close they are to us.

4. Why Classify? • When we classify items it helps us understand and apply their unique properties. • We know how to treat the matter, how to handle it, and what we might be able to do with it. • Take for instance clothing. • By classifying the material inside we know whether we can iron it or wash it with bleach.

5. Classifying Matter • In order to begin to comprehend matter – its composition, structure, and the reactions that happen in matter – we need to know how to basically classify matter. • What is matter? It’s any substance that has mass and is composed of atoms. • An atom is the smallest unit of an element that retains the element’s properties. • We’re beginning today by learning to classify matter based upon its composition = what matter is made of.

6. What is it?

7. Flow Chart: When we finish discussion, you’ll have an opportunity to fill this out.

8. Classifying Matter • When classifying matter the first question you must answer is: • “Does it have uniformity of composition?” • Meaning: does it appear it’s all the same stuff? • Sometimes you know, sometimes you are not sure. • Based upon observations, analysis, or what you know about it, you can answer.

9. The First Question • A uniform distribution means that you can’t see any obvious differences in the substance. • Does it look like it’s all the same thing? • If it does then it’s a homogeneous substance or mixture. • If it doesn’t then it’s a heterogeneous mixture.

10. Homogeneous Substances & Mixtures: Substances with matter so evenly distributed that it is difficult to distinguish between the substances that comprise it. • Fluid examples: Pool water (has dissolved substances mixed with water), the ocean, soda – What is dissolved in the carbonated water? pudding, cake batter • Solid examples: Can also be something like cake mixes or… • Metal alloys; Brass is a mixture of copper and zinc. • The likelihood of picking the same molecule is still small but it would be hard to choose different ones.

11. Pure substances • A fixed composition means that 100% is made of the same molecules. • Pure substance: Matter that always has exactly the same elements in a fixed composition. • Ex: Salt, Sugar • Each individual molecule is comprised of the same molecular composition in its smallest form. • Pure Substances are classified into two categories • Elements • Copper (Cu), Gold (Au) • Compounds • Salt (NaCl), Sugar (C6H1206) • The question to decide which is which is: “Can it be broken down into smaller, different parts?”

12. Pure Substances“Can it be broken down into simpler parts?” • If ‘no’ then = it’s an element • Elements: types of atoms on the periodic table • Gold • Au • Copper • Cu • If ‘yes’ then = Compounds: bonded elements • Salt: Sodium chloride • NaCl • Sugar: Glucose, Fructose • C6H1206

13. Elements: Pure Substances • Elements • The millions of substances and organisms known/found are made up of a few of only about 100 elements in millions of combinations. • See periodic table of elements pg 133 or back cover • Element= substance that only contains one type of atom. EXAMPLES: Any block on the periodic table. • Atom = the smallest particle of an element • Gold is an element, it mass is comprised of gold atoms • Most metallic elements are solids at room temperature • Common Examples: • Metals: Magnesium, Carbon, Aluminum, Copper, Plutonium • Given abbreviation based upon Latin origins (Berzelius) • Some, like mercury, are not.

14. Compounds: Pure Substances • Compounds: a substance formed from two or more atoms in a fixed ratio (given by the chemical formula • Can be broken down into either elements or compounds. • Are always formed of two or more elements joined in fixed proportion. • The proportion is defined by the chemical formula. • Ex: H2O = Water • Always 2 Hydrogen + 1 Oxygen • Another: C6H12O6 = Glucose • Always: 6 Carbon, 12 Hydrogen, 6 Oxygen

15. Mixtures: If it’s not all the same… • Mixtures: Composition of substances that is not uniform. • This means that the parts aren’t in the same proportion. • Meaning that there are a number of different things in different amounts making up the substance and the amounts of each is not ever exactly the same. • Mixtures can be homogeneous or heterogeneous.

16. Homogeneous Solutions: • Not all homogeneous substances are made of the same matter. Sometimes there are things mixed together but it’s hard to tell. • Solutions: are Homogeneous substances formed when solutes are dissolved in a solvent. • Basically a solvent is a fluid that something else dissolves in. • Water is the “universal solvent”. • This means that almost anything will dissolve in it. • There are other solvents, like oil, or vinegar. • The “something else” is called a solute: a substance that can be dissolved in a solvent. • Ex: Salt or sugar dissolved in water; it’s a mixture of substances but its difficult to distinguish between its parts. • Solutes dissolved in solvents form solutions.

17. Mixtures • Heterogeneous mixtures: mixture where the parts are noticeably different. • Ex: Beach sand • Notice how each of the parts is different. • It’s made up of shell, quartz, coral, rock, wood, and other stones and debris. • To decide if it’s a heterogeneous mixture think about the likelihood of picking the exact same item twice in a row.

18. Heterogeneous Mixtures:Suspensions and Colloids • Suspensions: Heterogeneous mixture of substances that will separate into layers over time • Ex: Salad dressing • Usually cloudy when mixed • The layers are and organic and aqueous. • One’s oil (organic) and the other’s water (aqueous)

19. Heterogeneous Mixtures:Suspensions and Colloids • Colloids: Homogeneous mixture of small, medium, and large substances that will not settle over time. • Ex: Homogenized milk (heating causes the fat to stay dissolved) • Vs. Fresh milk (a suspension that will separate over time)

20. Suspension v. Colloid • Suspensions and colloids differ from solutions due to the fact that they will scatter light. • This means that light waves will be redirected in various directions. • It will cause the light to appear as a cone as it travels through the colloid. • Have you ever seen a spot light shined through fog? • Fog is a colloidal mixture. • A colloid has a distinctive “milky” appearance.

21. Properties and Substances • One thing to note, other than knowing how and when to use matter, • Homogeneous Substances: have uniform properties throughout a substances while… • Heterogeneous Substances: have different properties for the different substances added.

22. Flow Chart: Complete 1 4 5 2 Solution Atom 6 Suspension Colloid 3 7 8

24. Any Questions For Me?I Have A few For You. Answer Answer Answer Answer Answer

25. Summary • By understanding how to classify a material we can better understand its properties. • Understanding its properties helps us to identify what it is. • This all helps us understand matter. • Now, write in your notes a reflection summary on how you could conduct a test that would determine if a sample was a pure substance or a mixture.

26. Summary • Matter is classified into pure substances and mixtures • Pure substances always have the same parts throughout • Mixtures consist of more than one simple substance in no specific consistency. • Mixtures can be categorized into homogeneous solutions, and heterogeneous suspensions, or colloids.

27. COMPLETE THIS CHART IN YOUR NOTES

28. Test Your UnderstandingIn-class Mini-lab. (25pts) • Objectives: • Using the knowledge you’ve gained from the lesson, identify what each of these sample materials are. • Directions: • Identify if the substance based upon its uniformity of composition. • Give a reason for your answer by describing the material. • Neatly present this in a chart-style paper.

29. Directions: Observe the samples and use their compositions to decide on their category • Hypothesis: (5pts) How can you use properties to classify substances? • Table: (5pts) Construct this table on your own paper and fill in all boxes. Be descriptive as possible. • Conclusion: (15 pts) Write 1 paragraph explaining if your hypothesis was correct and how you can use properties to categorize matter.

30. Directions: Observe the samples and use their compositions to decide on their category. • Hypothesis: (5pts) How can you use properties to classify substances? • Table: (5pts) Construct this table on your own paper and fill in all boxes. Be descriptive as possible. • Conclusion: (15 pts) Write 1 paragraph explaining if your hypothesis was correct and how you can use properties to categorize matter.