1. Introduction to Chemistry

2. Chapter 2 Properties of Matter
In this chapter:
Introduction to matter through a discussion of properties that you can observe.
How matter is classified
Properties used to described materials

3. Section 2.2 Classifying Matter
Classifying Items People classify objects for different reasons. Classifying foods into groups, such as grains, vegetables, and fruits helps people plan meals that maintain a healthy diet. Biologists classify organisms into groups that have similar characteristics, which makes the relationships among organisms easier to see. 1. Devise a classification system for the following items: orange, lime, plum, apple, pear, rose, violet, daisy, gold, and silver. 2. Explain what criteria you used to place items into each category of your classification system.

4. Inquiry Activity p. 37 Read the procedure, work in pairs
Purpose: Identify various properties of matter that can be used to describe materials.
Discuss materials with partner and record observations.
“Think about it” in Journal (Title and date)

5. Classifying Matter
Property (physical or chemical)– an essential or distinctive quality of thing; used to identify: gold – color, texture, streak
Properties are based on composition
Composition: Pure substances and mixtures

6. Pure Substances
Always has the same fixed, uniform composition (salt-every grain tastes the same)
2 Categories
Elements
Compounds

7. Pure Substance - Elements
Listed on Periodic Table
Cannot be broken down into simpler substances (copper → copper atoms)
Are written in symbols

8. Pure Substance - Compounds
Substance made from 2 or more simpler substances and can be broken down into those simpler substances (H20)
Properties of compound differ from elements (H & O gases; H2O – liquid)
Elements always in a fixed proportion - SiO2

9. Mixtures Properties can vary because composition is not fixed
Tend to retain some properties of individual substances
Classifications:
-Heterogeneous
-Homogeneous

10. Heterogeneous Mixtures
Hetero – “different”; genus – “kind”
Parts are noticeably different for each other
Sand: color, grain size

11. Homogeneous Mixtures
Substances are so evenly distributed that it is hard to distinguish between them
Kool-Aid (after it is stirred)
Brass – copper and zinc

12. Particle Size Based on the size of the largest particle Solution
Suspension
Colloid

13. Solution Dissolves to form homogeneous mixture
Too small to settle out; do not separate into distinct layers
Are not trapped in a filter
Can see through them; too small to scatter light
Ex: Tap water

14. Suspension Heterogeneous mixture that separates into layers
Larger particles can be filtered
Are cloudy; larger particles scatter light

15. Colloids
Particles are intermediate in size between small solution particles and the larger suspension particles
Do not separate into layers
Cannot be filtered; too small
Light is scattered; cloudy but uniform
Borderline between hetero- and homogeneous
Ex. Fog (low beam lights on car)

16. Section 2.2

17. Section 2.3-Chemical Properties
A chemical property is any ability to produce a change in the composition of matter.
Chemical properties can be observed only when the substances in a sample of matter are changing into different substances.
Examples:
Flammability
Reactivity

18. Flammability – ability to burn in the presence of oxygen.
Reactivity – describes how readily a substance combines chemically with another substance.
Oxygen highly reactive
Nitrogen not highly reactive

19. Chemical Change
Occurs when a substance reacts and forms one or more new substances.
3 common types of evidences:
Change in color-match turns black
Production of gas-vinegar+baking soda→CO2
Formation of precipitate – any solid that forms and separates from a liquid

20. Physical or Chemical Change
Physical – composition does not change
Sharpened pencil
Chemical – composition changes
Iron + oxygen → Fe2O3 (rust)