Pure Substances vs. Mixtures Physical and Chemical Changes

1. What's the "Matter"? Pure Substances vs. Mixtures Physical and Chemical Changes

2. Anything that has mass and takes up space is called matter. What is matter?

3. There are 2 types of matter: • Pure Substances • Mixtures

4. What are "pure substances"? Matter that has a fixed composition (Has a chemical formula) and definite properties. (chemical and physical)

5. There are two kinds of pure substances Elements Compounds

6. Element • Substance that cannot be separated or broken down into simpler substances by normal means. • Made of only 1 type of atom • Ex’s- any box on the periodic table • Rememberatoms are defined by their number of ____________ • Protons!

7. Elements can be atoms or molecules • ATOMS: • Only one atom • MOLECULE: • Two atoms (can be of the same element) bonded together

8. Compounds cont… • Substance made of atoms of 2 or more different elements that are CHEMICALLY combined. • This means they are BONDED at the electrons! • Has a chemical formula- ex ______________

9. When elements combine, it is in a definite way and this changes their properties Na- lethal if ingested Cl- lethal if ingested • NaCl- table salt

10. Molecules vs Compounds • Molecules are two or more atoms bonded together…but compounds must have two different elements • Ex- O2, NaCl, etc. REMEMBER: • Not all molecules are compounds, but all compounds are molecules…explain

11. Compounds Molecules made by two or more elements bonded together -always in a definite ratio Elements Molecules made of just one element What is a pure substance? Na (sodium) NaCl (sodium chloride/salt)

12. Characteristics of Pure Substances • Cannot be separated into simpler substances by physical methods (physical changes) • Atoms are bonded together in a fixed composition • Properties do not vary • Can be expressed with a chemical formula • Ex H2O, NaCl, H

14. What is a mixture? • Two or more substances that are physically combined. • (NOT chemically combined/bonded like a pure substance) • Can be separated into pure substances by physicalprocesses • Ex- Salt water can be separated into 2 pure sustances: __________ and _____________. • May have similar properties to the substances that make it (ex- sugar water)

15. Examples of Mixtures

16. Characteristics of Mixtures • Components retain their characteristic properties and can be separated by physical means. • http://videos.howstuffworks.com/hsw/22540-together-but-separate-suspensions-video.htm This sand and iron filings mixture can be separated using a magnet.

17. Two types of mixtures

18. Homogenous Mixtures • Homogenous mixtures look the same throughout • Types: solutions, alloys, etc. • Example: salt water, brass

19. Indicators of Homogenous Mixtures • Have the same composition throughout • Components are indistinguishable • Will not scatter light • Particle size is small

20. Can they still be separated by physical means ? YES!!! It may be more complicated, but it can be done…distillation , centrifugation

21. Homogeneous mixtures are called solutions • Solutions are … • homogenous mixtures that do not scatter light. • separated by physical means (including distillation or evaporation.) • created when something is completely dissolved in pure water. • Examples: sugar water, salt water

22. Parts of a Solution • Solute- substance that dissolves in solvent • ex. Salt (“U dissolve”) • Solvent- substance that does the dissolving (ex.water) Well, not really, because you don’t dissolve, but you get the picture 

23. Why don’t you dissolve? • You are not “Miscible” • Miscible- two or more liquids that can dissolve into each other (aka- soluble) • Immiscible- liquids that do NOT mix (aka- insoluble) • Ex- oil and water

24. Heterogenous Mixtures Heterogeneous mixtures are composed of large pieces that are easily separated by physical means (ie. density, polarity, metallic properties).

25. Indicators of Heterogenous Mixtures • Do not have same composition throughout • Components are distinguishable • Particle size is medium or large Examples: fruit salad, vegetable soup, etc.

26. Tyndall Effect • Scattering of light due to particles

27. Types of HeterogenousMixtures 1. Colloid –medium particles • Particles stay suspended in the mixture and scatter light (Tyndall effect) • Ex- mayonnaise, milk, fog

28. Types of HeterogenousMixtures 1. Suspension- large particles • Tyndall effect • Particles will settle out when the mixture is allowed to stand • Ex-muddy water, OJ with pulp

29. Chemical and Physical Properties

30. physical properties • Physical properties are those that we can determine without changing the identity of the substance we are studying. • Properties we can observe or measure • Ex- color, state of matter, etc

31. Examples of physical properties: • Hardness, color, melting point and density are all physical properties. • The physical properties of sodium (NaCl) metal • soft, lustrous • silver-colored metal • relatively low melting point • low density.

32. DENSITY Mass per unit volume Calculated by: Density= Mass/Volume D=M/V Units: g/mL g/cm3

33. Viscosity • Resistance to flowing Maple Syrup- High Viscosity Water- Low Viscosity

34. Ductility • Ability to be drawn into a thin wire

35. Malleability • Ability to be hammered into thin sheets without shattering

36. Hardness • A substance’s resistance to being scratched

37. Solubility • Ability to dissolve in water • Yes! It is a physical property because you do not need to alter identity of the substance to determine solubility.

38. Conductivity • Ability to carry electricity High Conductivity (the liquid is able to let electrons flow to complete the circuit Low Conductivity (the liquid is NOT able to let electrons flow to complete the circuit

39. What is a superconductor? • Watch this video and try to write a one to two sentence explanation of “what is a superconductor?”

40. Video on Superconductors

41. Other examples of physical properties…. boiling point shape density freezing point melting point temperature

42. Chemical Properties • Describe the way a substance can change or react to form other substances. (what bonds they will form) • (NOT the actual reaction- that’s a chemical change) • Must be determined using a process that changes the identity of the substance • (chemical reactions involve breaking and making new bonds)

43. How can chemical properties be identified? • One of the chemical properties of alkali metals such as sodium and potassium is that they react with water. To determine this, we would have to combine an alkali metal with water and observe what happens. • In other words, we have to define chemical properties of a substance by the chemical changes it undergoes.

44. Ex’s of Chemical Properties • Reactivity: ability of a substance to combine CHEMICALLY (at the electrons) with another substance (to form a compound)

45. Flammability • Ability of a material to burn in the presence of Oxygen.

46. Alkalinity • Ability to neutralize acids

47. Physical vs Chemical Properties • Do work on your notes sheet • Then read pages 47-48, look at Math Skills and then do questions 1-3 in “Practice” section.

48. What is a physical change? • A change that does not change the chemical composition of a substance. • Ex: changes in size, shape, appearance, etc. • Why? The form or appearance has changed, but the properties of that substance are the same (i.e. it has the same melting point, boiling point, chemical composition, etc.)

49. PHYSICAL CHANGE: Changes in State Melting, Boiling, Freezing Changes in Color Conducting electricity Dissolving Hammering into a sheet Drawing into a wire PHYSICAL PROPERTY Melting Point, Boiling Point, Freezing Point Color Conductivity Solubility Malleability Ductility Physical Changes

50. What are chemical changes? • A chemical change occurs when a substance changes into something new. • This occurs due to heating, chemical reaction, etc. • You can tell a chemical change has occurred if the density, melting point or freezing point of the original substance changes. Many common signs of a chemical change can be seen (bubbles forming, mass changed, etc).