Understanding Matter: Composition & Properties

1. Chapter 1 Chemistry: The Science of Matter Section 1.1: The Puzzle of Matter Section 1.2: Properties and Changes of Matter

2. Section 1.1 Objectives • Classify matter according to its composition. • Distinguish among elements, compounds, homogeneous mixtures, and heterogeneous mixtures. • Relate the properties of matter to its structure.

3. Composition, Structure and Behavior • Chemistry- the science that investigates and explains the structure and properties of matter. • Matter- anything that takes up space and has mass • Mass- the measure of the amount of matter that an object contains

4. Matter • Matter is all around you. • Phone • Your neighbor • The desk • The metal of your chair • The air you are breathing • What isn’t matter • Heat • Light • Thoughts • Ideas • Radio waves • Magnetic fields

5. Mass • On earth we equate mass with weight. • A bowling ball has a larger mass than a tennis ball. • I have more mass than the text book.

6. Matter • The structure of matter refers to its composition-what is it made of and how is it organized • The properties of matter describe the characteristics and behavior of matter. • Changes matter undergoes

7. Comparing Composition and Behavior (Figure 1.2 page 5) • Salt and Water • Salt is Na and Cl • Water is H and O • You can wash you hair in water, but not in salt. And you sprinkle water over popcorn. • Aspirin and Sucrose • Both are composed of C, H, and O • You wouldn’t use aspirin to sweeten cereal or use sucrose for a headache

8. Properties • You can determine some of the properties of a particular chunk of matter by examination and manipulation. • What is its color? • Is it a solid, liquid or gas? • Is it soft or hard? • Does it dissolve in water?

9. Properties of Iron • Strong, but can be flattened and stretched • Does not dissolve in water • Turns to a liquid at high temperatures • Is a gray, shiny solid • Is attracted to a magnet • Conduct electricity

10. Properties and Composition • You may be able to determine many properties of a piece of matter by examining it and doing some simple tests. • However, you can not determine what it is composed of just by looking at it.

11. Examining Matter: The Macroscopic View of Matter • The macroscopic view of matter is one in which you touch, smell, taste and see.

12. The Submicroscopic View of Matter • Gives you a glimpse into the world of atoms • You cannot see this world even with the most powerful microscopic. • Matter is made up of atoms • Atoms are so small that a period at the end of a sentence is made up of 100,000,000,000,000,000,000 (100 quintillion) carbon atoms. • If you could count all 100 quintillion atoms at a rate of three per second it would take you a trillion years to finish counting.

13. Macro, micro, submicro • Macroscopic – I can see with my “naked” eye • Microscopic – I need a microscope to see • Submicroscopic – I can’t see even with the most powerful microscope

14. Scanning Tunneling Microscope (STM) • Although you cannot see atoms the STM can produce images on a computer screen that show the location of individual atoms. • Platinum

15. Using Models in Chemistry • In chemistry you will use macroscopic and sub-microscopic models to understand certain concepts. • Scientific model- a thinking device, built on experimentation, that helps us to understand and explain macroscopic observations.

16. Models • A model for the atom was discussed in Greece about 2,500 years ago. However, this was not a scientific model. • The scientific model of the atom was not proposed until the 1800’s and it has with stood much experimentation with little changes.

17. Classifying Matter • Matter can be classified by its composition • There are two main types of classifications • Qualitative- an observation made without measurement. • Quantitative- an observation made with measurement

18. Qualitative vs. Quantitative • Qualitative • There are students in this room • Sucrose contains carbon, oxygen and hydrogen • Quantitative • There are 24 students in this room • Sucrose contains 42.1 g of carbon, 51.4 g of oxygen and 6.5 g of hydrogen.

19. Pure vs. Mixture • Matter can be classified by its purity. • Is the matter pure or is it a mixture? • Pure in chemistry means it contains only the same substance. • Substance- matter with the same fixed composition and properties. • Can be an element or a compound • Any sample of pure matter is a substance

20. Substances • The bag of sugar you buy at the store is pure sucrose. It all has the same properties and a fixed composition. Therefore, it is a substance.

21. Mixed Matter • Mixed matter is referred to as a mixture. • Mixture- combination of two or more substances in which the basic identity of the substances are not changed. • Mixtures do not have a specific composition. • Mixtures can be separated into its components by physical means.

22. Separating Mixtures • One way is by physical changes. • Physical change- a change in matter that does not involve a change in the identity of individual substances. • Boiling • Freezing • Melting • Evaporation • Dissolving • Crystallization

23. Physical Properties • Separation by physical changes takes advantage of the physical properties of the mixture. • Physical properties- characteristics that a sample of matter exhibits without any changes in its identity • Solubility • Melting and boiling point • Color • Density • Electrical conductivity • Physical state (solid, liquid or gas)

24. Types of Mixture • There are two types of mixtures: • Heterogeneous • Hetero means “different” • Homogeneous • Homo means “the same”

25. Heterogeneous Mixture • Heterogeneous Mixture- a mixture that does not have a uniform composition. • You can see the different composition. • Examples: • Granite • Chef Salad • Lucky Charms Cereal • Orange Juice with pulp

26. Homogeneous Mixture • Homogeneous Mixture- a mixture with a uniform composition. • You cannot tell that it is composed of more than one substance • Another name is a solution • Examples: • Salt water • Tea • Sugar water

27. Solutions • Homogeneous mixture • Examples: • Salt water • Gasoline • Air • Steel

28. Alloys • Alloys- solid solutions that contain different metals and sometimes nonmetallic substance • Table 1.1 page 23

29. Table 1.1 Some Common Alloys

30. Solutions • When you are dissolving a substance into another substance there are two important terms: • Solute – the substance being dissolved • Solvent – the dissolving agent • Salt Water • Solute = NaCl • Solvent = H2O

31. Aqueous Solution • Aqueous Solution- a solution in which the solvent is water. • Examples: • Soda • Tea • Contact-lens cleaner • Clear cleaning liquids • Most processes of life take place in aqueous solutions.

32. Substance: Pure Matter • You and everything around you is made up of chemicals.

33. Elements: The Building Blocks • If you classify an unknown piece of matter as pure; it means that it is made up of one substance • There are two types of substances • Compounds • Elements

34. Elements • Elements- a substance that cannot be broken down into simpler substances. • Simplest form of matter • Building blocks for other types of matter • All substance in the universe are: • Elements • Compounds formed from elements • Or mixtures of elements and compound

35. Elements • 118 elements • Examples: • Gold • Carbon • Lead • Elements combine to form millions of compounds. • Chemical elements are often referred to as the building blocks of matter

36. Elements • 118 elements • 90 occur naturally • Less than half of these are abundant • The remainder are synthesized

37. Organizing the Elements • Elements are organized in the Periodic Table • The periodic table tells you: • Name • Symbol • Atomic mass

38. Symbols • The symbols of the elements are extremely important to know. • You will only have to know the most common ones. • The symbols are a one to two letter representation of the elements. • Not all the symbols are the first or second letter of the elements name

39. Symbols • Oxygen • O • Hydrogen • H • Bromine • Br • Chlorine • Cl

40. Table 1.2 Some Historic Chemical Symbols

41. Compounds Are More Than One Element • Compound – a chemical combination of two or more different elements joined together in a fixed proportion. • Every compound has its own fixed composition • Therefore, every compound has unique chemical and physical properties. • The properties of a compound are different from the properties of the elements that make them up.

42. Compounds • More than 10 million are known (still growing) • New natural compounds are being isolated from plants and colonies of bacteria. • New compounds are also being synthesized in labs. • Examples • Sucrose • Salt • Water

43. Formulas of Compounds • Formula – a combination of the chemical symbols that show what elements make up a compound and the number of atoms of each element. Sucrose: Aspartame:

44. Table 1.3 Some Common Compounds

45. Review • What is the difference between an element and a compound? • What is the difference between a homogeneous mixture and a heterogeneous mixture? • What is the difference between a mixture and a compound?