Classifying Matter: Elements, Compounds, and Mixtures

1. Classifying Matter:Elements, Compounds, and Mixtures

3. Pure Substances • A sample of matter that has definite chemical and physical properties. Atoms Elements Compounds Molecules

4. Elements • pure substance that cannot be separated into simpler substance by physical or chemical means.

5. Elements • In 1813, a system of representing elements with symbols was introduced. • Each symbol consists of one or two letters. • Two letters are needed for a chemical symbol when the first letter of that element’s name has already been used.

6. Common Elements

7. Compounds Pure substance composed of two or more different elements joined by chemical bonds. • Made of elements in a specific ratio that is always the same • Has a chemical formula • Can only be separated by chemical means, not physically H2O NaCl CO2

8. Compounds • Compounds are also pure substances. • Water is a compound. • Water can be broken down into simpler substances – hydrogen and oxygen.

9. Mixtures • A combination of two or more pure substances that are not chemically combined. • substances held together by physical forces, not chemical • No chemical change takes place • Each item retains its properties in the mixture • They can be separated physically Chem4kids.com

10. Is it uniform throughout? • If the answer is yes, the matter is homogeneous (looks the same throughout). • That leads us to another question.

11. Homogeneous Mixtures • A mixture that appears to be the same throughout. • It is “well mixed.” • The particles that make up the mixture are very small and not easily recognizable.

12. Examples of homogeneous mixtures Milk, toothpaste, and mayonnaise are homogeneous mixtures.

13. Solutions • A solution is a type of homogeneous mixture formed when one substance dissolves in another. • It is the best mixed of all mixtures. • A solution always has a substance that is dissolved and a substance that does the dissolving. • The substance that is dissolved is the solute and the substance that does the dissolving is the solvent.

14. Ocean water is a solution

15. Water as a solvent • Many liquid solutions contain water as the solvent. • Ocean water is basically a water solution that contains many salts. • Body fluids are also water solutions.

16. The universal solvent: Water

17. SOLUTIONS HAVE 2 PARTS • SOLUTE – The substance being dissolved • SOLVENT- The substance doing the dissolving • sugar=solute • Water = solvent

18. Types of solutions Solute Solvent Example Metals dissolved in metals are called alloys.

19. Alloys Stainless steel is a mixture of iron and chromium. Brass is an alloy of copper and zinc.

20. Is it uniform throughout? • If the answer is no, the matter is a heterogeneous mixture. • Considered the “least mixed.” • Does not appear to be the same throughout. • Particles are large enough to be seen and to be separated from the mixture.

21. Examples of heterogeneous mixtures • Sand and pebbles • Oil and water • Powdered iron and powdered sulfur

22. Granite is a heterogeneous mixture.

23. COLLOID – a liquid mixture - can be considered a homogeneous and sometimes heterogeneous mixture ex: milk SUSPENSION – a liquid mixture - heterogeneous -ex: Italian dressing

25. Colloids • In a colloid the particles are mixed together but not dissolved. • The particles are relatively large and are kept permanently suspended.

26. Colloids • A colloid will not separate upon standing. • The particles are constantly colliding, and this allows a colloid to scatter light – thus colloids often seem cloudy.

28. Examples of homogeneous mixtures Milk, toothpaste, and mayonnaise are homogeneous mixtures. THESE ARE EXAMPLES OF COLLOIDS

29. Mixtures vs. Compounds http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/elements_com_mix_6.shtml

30. Can you identify the following? You will be shown a series of photos. Tell if each photo represents an item composed of an element, compound, or mixture. Review: • An element contains just one type of atom. • A compound contains two or more different atoms joined together. • A mixture contains two or more different substances that are only physically joined together, not chemically. • A mixture can contain both elements and compounds.

31. Element, Compound, or Mixture? Rocks

32. Element, Compound, or Mixture? Rocks

33. Element, Compound, or Mixture? Copper

34. Element, Compound, or Mixture? Cu Copper

35. Element, Compound, or Mixture? Jelly Beans

36. Element, Compound, or Mixture? Jelly Beans

37. Element, Compound, or Mixture? Table Sugar

38. Element, Compound, or Mixture? Table Sugar C12H22O11

39. Element, Compound, or Mixture? Diamond

40. Element, Compound, or Mixture? C Diamond

41. Element, Compound, or Mixture? Tea

42. Element, Compound, or Mixture? Tea

43. Element, Compound, or Mixture? Salt

44. Element, Compound, or Mixture? NaCl Salt

45. Element, Compound, or Mixture? Neon Gas

46. Element, Compound, or Mixture? Ne Neon Gas

47. Element, Compound, or Mixture? Salad

48. Element, Compound, or Mixture? Salad

49. Element, Compound, or Mixture? Pure Water

50. Element, Compound, or Mixture? H2O Pure Water