1. Introduction to Chemistry & Classifying Matter (Section 2.1)

2. Matter Anything that has mass and takes up space
Comes in many different forms

3. Mass A measurement reflecting the amount of matter
Mass and weight are not the same
Weight measures the earth’s gravitational pull on
matter

4. Chemistry at Different Levels
Macroscopic (very large) to Sub-Microscopic level (very small)
Chemistry explains how changes at the sub-microscopic level lead to changes at the macroscopic level

5. Stuff
Matter
Elements
Atoms
Particles

6. Mountains-->Ore-->Copper-->Atoms-->Subatomic Particles

7. Classifying Matter
Based on their compositions, materials can be divided into pure substances and mixtures

8. Pure Substances Matter that always has exactly the same composition
Every sample of a given substance has the same properties because a fixed, uniform composition
Substances can be classified into two categories
Elements
Compounds

9. Elements
A substance that cannot be broken down into smaller, simpler substances
An atom is the smallest particle of an element
An element has a fixed composition because it contains only one type of atom
No two different elements contain the same type of atom

10. 91 naturally occurring elements, plus others developed in the lab
Each element has a unique name and symbol
Are not equally abundant

11. Symbols for Elements
Symbols for elements are either one or two letters
The first letter is always capitalized and the second letter is not
Symbols allow scientists from different countries to communicate without confusion
Examples:
Aluminum = Al
Hydrogen = H
Calcium = Ca
Silver = Ag

12. Compounds
Is a substance that is made from two or more simpler substances and can be broken down into those simpler substances
A compound always contains two or more elements joined in a fixed proportion

13. Mixtures
A combination of two or more pure substances, in which each pure substance retains its individual properties
Heterogeneous Mixtures
Does not blend smoothly
Individual substances remain distinct
Homogeneous Mixtures
Constant composition throughout

14. Solutions, Suspensions, & Colloids
The size of the particles in a mixture have an effect on the properties of the mixture
Based on the size of its largest particles, a mixture can be classified as a solution, a suspension, or a colloid

15. Solutions They do not separate into distinct layers
Formed when substances dissolve and form a homogeneous mixture
The particles in a solution are too small to settle out of the solution, be trapped by a filter, or scatter light
They do not separate into distinct layers
None of the substances get trapped when passed through a filter
Light can pass through without being
scattered in all directions

16. Suspensions
Is a heterogeneous mixture that separates into layers over time
Suspended particles settle out of a mixture or are trapped by a filter (larger particles than that in the solution)
Suspensions are cloudy because the larger particles can scatter light in all directions

17. Colloids
Contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension
Does not separate into layers
Cannot use a filter to separate parts
Light is scattered when going through a colloid
The scattering of light is a property that can be used to distinguish colloids and suspensions from solutions

18. http://www. google. com/url