2.1 Classifying Matter
Why do we classify matter? Different substance have different properties
How do we classify matter? By their composition (Latin for “a putting together”)
Pure Substances
What is a pure substance? Matter that always has the same composition
What are a few examples of pure substances? Salt Sugar
Pure Substance Continued
What can we say about the properties of pure substances? They have the same properties
What are the categories of Pure Substances? Elements Compounds
Elements
What is an element? Substance that cannot be broken down into simpler substances
How many are there? About 100
Elements Continued
What is an atom? The smallest piece of an element
Why do elements have fixed composition? It only contains one type of atom
Examples of Elements
Aluminum – solid metal Carbon – main element of life, used for writing
Oxygen – what we breathe Nitrogen – inert gas, important ingredient for fertilizer
Symbols for Elements
One or two letters, first letter is always capital
Many symbols come from Latin names of elements, Au for gold stands for aurum
Compounds What is a compound?
A substance that is made from two or more simpler substances.
What can compounds be broken down into? Elements or smaller compounds
Properties of Compounds Are they the same as the
elements that make them? No, for example water puts out fire, but Oxygen and Hydrogen are flammable
Is the composition of a compound fixed? Yes, the parts always have the same proportions
Mixtures
What is a mixture? Combination of multiple pure substances
Does a mixture have fixed composition? No, the amounts of pure substances can vary
Types of Mixtures
How many types of mixtures are there? 2
What are the types called? Heterogeneous Homogeneous
Heterogeneous Mixtures Hetero – from Greek, means different
Genus – from Greek, means kind
These mixtures are noticeably different
Homogeneous Mixtures Homo – from the Greek,
means “same” This type of mixture has parts that cannot be distinguished from one another
Solutions
Solutions are formed when a substance dissolves in another substance and makes a homogeneous mixture
Example – tap water
Properties of Solutions They do not separate into distinct layers over time
If you filter the solution, there will not be any particles that are trapped in the filter
Light can pass through them
Suspensions
Heterogeneous mixture that separates into layers over time
Filters can separate the parts
Colloids
Contains particles that are bigger than ones in solutions, so they don’t dissolve
Particles are smaller than suspensions, they don’t separate over time