1. Physical and Chemical Properties
More About Matter
Physical and Chemical Properties

2. Physical vs. Chemical Properties
Physical Properties
Observed without changing identity of substance.
Ex: color, hardness, density, odor, malleability, ductility, MP temp.
Chemical Properties
Observed during chemical changes
Ex: flammable, explosive, corrosive, rusts, decomposes

3. Chemical vs. Physical Changes
Does not alter chemical composition.
Substance still has same chemical formula.
Ex: bend, cut, grind, dissolve, undergo a phase change
Chemical Change
Chemical composition changes as a reaction occurs.
New products formed.
Ex: cook food, sour milk, burn wood, explode dynamite

6. What Type of Change?

7. What Type of Change? H2O(s) → H2O(l) 2H2O (l) → 2H2(g) + O2(g)
NaCl(s) → NaCl(aq)
CH4(g) + O2(g) → CO2(g) + H2O(g)

8. Is it Chemical or Physical?
Sometimes it is possible to determine a chemical change using the naked eye.
Things to look for:
Gas bubbles produced, unusual color change, new odor produced, precipitate forms
Precipitate: an insoluble solid that forms when two solutions are mixed.

9. Pure Substance vs. Mixtures
Types of Matter
Pure Substance vs. Mixtures

10. Elements (Pure Substance)
Made up of atoms of one specific type
Have specific physical and chemical properties.
Cannot be broken down by chemical reactions
Ex: Fe, K, Na, Si

11. Compounds (Pure Substance)
Two or more different elements chemically
bonded together.
Have different chemical and physical properties
than elements that make them up.
Definite fixed proportions by mass.
Ex: C6H12O6, MgCl2, CO2, NaCl
The numbers written below the symbols are called “subscripts” and let us know about the number of each type of atom in the compound

12. Mixtures Two or more pure substances physically combined.
Mixtures can be solid, liquid or gaseous.

13. Mixture’s Composition is Not Fixed
Can vary depending on how much of each component is added.
Ex: One teaspoon of sugar in water or ten teaspoons it’s still a sugar water mixture.

14. Retaining Their Properties
Substances in mixtures retain their own properties.
Ex: Iron filings (Fe) and sand (SiO2)
Even if mixed the iron retains its magnetic properties

15. Element, Compound or Mixture?

16. Types of Mixtures

17. Homogeneous Mixtures
Components are distributed uniformly at the molecular level.
All true solutions are homogeneous.

18. If you see (aq) it is a homogeneous mixture
Aqueous = (aq)
dissolved in water or “in solution”
Ex: NaCl (aq)

20. How to Tell if a True Solution
Tyndall Effect
Suspensions and colloids have larger particles that will scatter a beam of light. In a true solution the light will not be scattered

23. Heterogeneous Mixtures
Components are not uniformly distributed at the molecular level.
Colloids and suspensions are included in this category.

25. Separating Mixtures
Components retain their own properties, so use these properties to separate them.
Ex: density, particle size differences, solubility differences, BP temperature, magnetic properties

27. Filtration Ex: Separate water & sand
Can be used to separate heterogeneous mixtures
Technique cannot be used to separate components of solutions
Separates components with different particle sizes.
Use various types of filter paper

28. Separatory Funnel Ex: Separate oil and water What type of mixture?
Used to separate out two liquids that do not mix together.

29. Evaporation Ex: Separate sugar from water What type of mixture?
Separate out a liquid from a dissolved solid.
Use evaporating dishes or watch-glass
Liquid is allowed to evaporate off and solid crystals are left behind

30. Chromatography
Solvent runs up paper and components separate out along length of paper depending on level of attraction to solvent.
Ex: Separate different types of chlorophyll

31. Distillation
Separates two or more liquids, due to differences in boiling point temp.
Ex: Separate alcohol and water
What type of mixture?
Each liquid reaches its B.P., becomes a gas and then is recondensed in its pure state.

33. Density Calculating

34. Density
Because all matter has mass and volume, all matter has density.
No matter the size of the sample, the density doesn’t change.
It is a physical property.
See Reference Table S for the density of elements.
D = M V
Density can change under different pressure and temperature conditions.
This is especially true for gases which can expand and contract in volume easily.

35. Density of Water Density of Pure Water = 1.0 g/ml
If a substance has a density greater than water it will sink, if not it will float.
When you dissolve a substance in water it makes it more dense.

36. Measuring Density (D = M/V)
Mass
Measured on a scale, often you need to use a weighing dish or a beaker.
Volume
Can be measured in different ways.
For solids the method of water displacement is often used.

37. Density column
Coke vs Diet coke

38. Clips Separating Mixtures http://youtu.be/fJXBlfwB_Nw Distillation

39. Cool Clips Showing Chemical Change
Chemical Reactions (Bill Nye)
Steve Spangler (clock reactions)
Diet Coke and Mentos