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

2. Everything that has mass and takes up space is called matter.
What is matter?
Everything that has mass and takes up space is called matter.
Basic definition of matter.

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

5. There are two kinds of pure substances
Elements
Compounds

6. Elements
Substance that cannot be separated or broken down into simpler substances by chemical means.
Ex’s- any box on the periodic table
Made of only 1 type of atom
The smallest unit of an element that
maintains the properties of that element
HUH?

7. The smallest unit of an element that maintains the properties of that element???
The element sodium has certain properties
11 protons, 11 electrons…boiling point, etc

8. Compounds cont…
Substance made of atoms of 2 or more different elements that are CHEMICALLY combined.
Elements are combined in a definite way and this changes their properties
Na- lethal if ingested Cl- lethal if ingested
NaCl- table salt

9. Molecules Two or more atoms bonded together… Ex- O2, NaCl, etc.
Not all molecules are compounds, but all compounds are molecules…explain

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

11. Characteristics of Pure Substances
Cannot be separated into simpler substances by physical methods (physical changes)
Fixed composition
Properties do not vary
Can be expressed with a chemical formula
Ex H2O, NaCl, H
Basic characteristics of pure substance:

13. What is a mixture?
Mixtures are two or more substances that are physically combined.
(NOT chemically combined like a pure substance)
May be separated into pure substances by physical methods

14. Examples of Mixtures

15. Characteristics of Mixtures
Components retain their characteristic properties and can be separated by physical means.
Basic identification of a mixture.
This sand and iron filings mixture can be separated using a magnet.

16. Two types of mixtures

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

18. Indicators of Homogenous Mixtures
Have the same composition throughout
Components are indistinguishable
Will not scatter light
Particle size is small
Brainstorm more examples of homogenous mixtures.

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

20. 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

21. 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 

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

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

24. 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.
Brainstorm more examples of heterogenous mixtures.

25. Tyndall Effect
Scattering of light due to particles

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

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

28. What kind of changes does matter undergo?
Physical
Chemical

29. 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

30. Physical Properties of Matter
Property
Description
Example
Hardness
Ability of 1 substance to scratch another
Diamond can scratch glass
Viscosity
Resistance to flowing
Water= low visc.
Honey= high visc.
Solubility
Ability to dissolve in water
NaCl dissolves easily in water so it’s soluble

31. Physical Properties of Matter
Property
Description
Example
Superconductor
Substance that conducts electricity at lower temperatures
Tin, aluminum, used in trains
Semiconductor
Substance that has a resistance b/w a conductor & insulator
Silicon-used in computers or radios

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

33. Physical Properties of Matter

34. 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.

35. What is a physical change?
A physical change occurs when the substance changes physically but does not change its chemical composition.
For example: water freezing into ice, cutting a piece of wood into smaller pieces, etc.
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.)
Definition of physical changes.

36. Physical Changes Temperature Color Conducting electricity Dissolving
Melting
Boiling
Freezing
Color
Conducting electricity
Dissolving
Physical changes are characterized by the following:

37. What are chemical properties?
Chemical properties describe the way a substance can change or react to form other substances.
These properties, then, must be determined using a process that changes the identity of the substance of interest.

38. 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.

39. 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).
Definition of chemical change.

40. Characteristics of Chemical Changes
Baking soda reacting w/ vinegar
You can’t go back to the original substances after a chemical change (reaction) has occurred!!
Chemical Changes are characterized by the following:
Burning wood

41. Comparison of Physical and Chemical Properties

42. Conservation of Matter
Law of
Conservation of Matter
There is no observable change in the quantity of matter during a chemical reaction or a physical change.
In other words, matter cannot be created nor destroyed. It is just converted from one form to another
Definition of Conservation of matter.