1. Chapter 2
Properties of Matter

2. 2.1 Classifying Matter Key Concepts
Why are elements and compounds classified as pure substances?
How do mixtures differ from pure substances?
What is the main difference among solutions, suspensions, and colloids?

3. 2.1 Classifying Matter
Pure Substances matter that always has exactly the same composition is classified as a pure substance. Examples: table salt and table sugar Every sample of a given substance has the same properties because a substance has a fixed, uniform composition.

4. 2.1 Classifying Matter Elements
An element is a substance that cannot be broken down into simpler substances
There are only about 100 known elements
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 elements contain the same type of atom
Examples of elements: mercury, carbon, oxygen, etc.

5. 2.1 Classifying Matter
At room temperature (20°C or 68°F), most elements are solids, including the elements aluminum and carbon.
Some elements are gases at room temperature, such as oxygen and nitrogen.
Only two elements are liquids at room temperature, bromine and mercury (both of which are extremely poisonous.

6. 2.1 Classifying Matter Symbols for Elements
Each element has its own unique symbol
The symbols exist as one or two letters with the first letter always represented with a capital letter.
The symbols allow scientists who speak different languages to communicate without confusion

7. 2.1 Classifying Matter Compounds
A compound is a substance that is made from two or more simpler substances and can be broken down into those simpler substances
The simpler substances are either elements or other compounds.
The properties of a compound differ from those of the substances from which it is made.

8. 2.1 Classifying Matter
A compound always contains two or more elements joined in a fixed proportion.
Mixtures
The properties of a mixture can vary because the composition of a mixture is not fixed.
Example: salsa
Mixtures can be classified by how well the parts of the mixture are distributed throughout the mixture

9. 2.1 Classifying Matter Types of Mixtures: heterogeneous, homogeneous
Heterogeneous mixtures – the parts of the mixture are noticeably different from one another.
Hetero – different
Genus – kind
Example : sand
Homogeneous mixtures – the substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from one another
Homo - same

10. 2.1 Classifying Matter Solutions, Suspensions, and Colloids
Based on the size of its largest particles, a mixture can be classified as a solution, suspension, or a colloid
Solutions: When substances dissolve and form a homogeneous mixture, the mixture that forms is called a solution.
Examples: windshield wiper fluid, tap water
Liquid solutions are easy to recognize. They do not separate into distinct layers over time

11. 2.1 Classifying Matter Solutions
The particles in a solution are too small to settle out of the solution, be trapped by a filter, or scatter light
Suspensions
A suspension is a heterogeneous mixture that separates into layers over time.
Example: vinegar and oil, “shake well”
You could use a filter to separate sand from water in a sandy water mixture.
Larger particles can be separated from the mixture
Suspensions are cloudy

12. 2.1 Classifying Matter Colloids Example: milk, fog
A colloid contains some particles that are intermediate in size between the small particles in a solution and the large particles in a suspension
Colloids do not separate into layers
Cannot use a filter to separate parts of a colloid

13. 2.1 Classifying Matter
The scattering of light is a property that can be used to distinguish colloids and suspensions from solutions

14. 2.2 Physical Properties
Viscosity, conductivity, malleablility, hardness, melting point, boiling point, and density are examples of physical properties
A physical property is any characteristic of a material that can be observed or measured without changing the composition of the substances in the material

15. 2.2 Physical Properties
Viscosity – the tendency of a liquid to keep from flowing – the resistance to flowing
Examples of high viscosity : honey, corn syrup
Examples of low viscosity: vinegar, soda
The viscosity of a liquid usually decreases when heated.

16. 2.2 Physical Properties Conductivity
A material’s ability to allow heat to flow
Metals have high conductivity and are called conductors.
If a material is a good conductor of heat, it is usually also a good conductor of electricity.
Wood is not a good conductor of heat (wooden spoon)

17. 2.2 Physical Properties Malleability
The ability of a solid to be hammered without shattering.
Most metals are malleable.
Solids that shatter when struck are brittle.

18. 2.2 Physical Properties Hardness
One way to compare the hardness of two materials is to see which one of the materials can scratch the other.
Melting and Boiling Points
The temperature at which a substance changes from solid to liquid is its melting point
The temperature at which a substance boils is its boiling point.

19. 2.2 Physical Properties Density
Can be used to test the purity of a substance.
Density is the ratio of the mass of a substance to its volume.
Physical properties are used to identify a material, to choose a material for a specific purpose, or to separate the substances in a mixture.

20. 2.2 Physical Properties Using properties to separate mixtures
Filtration and distillation are two common separation methods.
Filtration is a process that separates materials based on the size of their particles.
Distillation is a process that separates the substances in a solution based on their boiling points.

21. 2.2 Physical Properties Recognizing Physical Changes
A physical change occurs when some of the properties of a material change, but the substances in the material remain the same.
Some physical changes can be reversed, some cannot.

22. 2.3 Chemical Properties
Chemical properties can be observed only when the substances in a sample of matter are changing into different substances.
A chemical property is any ability to produce a change in the composition of matter.
Flammability is a material’s ability to burn in the presence of oxygen.
Reactivity is the property that describes how readily a substance combines chemically with other substances.

23. 2.3 Chemical Properties Recognizing Chemical Changes
A chemical change occurs when a substance reacts and forms one or more new substances.
Three common types of evidence for a chemical change are a change in color, the production of a gas, and the formation of a precipitate.
A precipitate is any solid that forms and separates from a liquid mixture.

24. 2.3 Chemical Properties
When matter undergoes a chemical change, the composition of the matter changes.
When matter undergoes a physical change, the composition of the matter remains the same.