Chapter 2
Properties of Matter
2.1 – Classifying Matter
Pure substance – has exactly
same composition (made of the same atoms or
molecules)
Elements (atoms)
Compounds (molecules)
Elements
About 110 elements
Cannot be broken down
Contains only one kind of atom
Elements
Different elements are made from different types of atoms
Represented by symbols
1st letter always capitalized
2nd letter never capitalized
Compounds
Made of 2 or more elements
in fixed proportions
(molecules)
Can be broken down
Properties differ from
elements it is made of
Mixtures
2 or more substances mixed
together
Parts are physically mixed, NOT chemically combined
Not in fixed proportions
Not evenly distributed
Keeps some properties from each substance (ingredients)
Can be separated
Types of Mixtures
Heterogeneous mixtures
“hetero” = different
Not the same throughout
Can see the different parts
Examples: sand, concrete,
hamburger, stew
Types of Mixtures
Homogeneous mixtures
“homo” = same
Evenly mixed
Appears the same throughout
Cannot see different parts
Examples: salt water, soda,
lemonade, stainless steel
Solutions
Solution: is a homogeneous mixture with substances dissolved in a liquid
Solvent: is usually a liquid that dissolves another substance (water is the universal
solvent) Ex. water, alcohol, paint thinner
Solute: is the substance being dissolved
Ex. Salt, sugar, baking soda,
Solutions can be separated by distillation
Examples: salt water, punch, tea
Suspensions
Heterogeneous mixture
Separates over time
Suspensions can be separated by filtration
Example: dirt and water, Italian dressing
Colloids
Homogeneous mixture
Cloudy, creamy
Cannot see through
Do not separate into layers
Cannot filter
Examples: fog, milk, lotion
2.2 Physical Properties
Any characteristic observed without changing composition of the substance
Example: mass, volume, weight, density, color, size, shape, texture, odor,
Examples
Viscosity – resistance to flowing
Oil, honey, syrup
Conductivity – ability to allow
heat and electricity to flow
Metals are good conductors
Malleability – ability of a solid
to be hammered into a thin sheet
Gold, Aluminum
Density – the amount of mass squeezed into the volume (space)
used to test the purity of a substance
D=M/V
All elements have unique densities
Density is the property that determines whether an object floats or sinks
Hot water vs. cold water
Melting point – the temperature when a solid becomes a liquid
Water – 0o C or 32o F
Also the freezing point
Boiling point – the temperature when a liquid
becomes a gas
o
o
Water – 100 C or 212 F
Different substances have diff. boiling and melting points
Using Physical Properties
To identify materials
Solving crimes
To choose materials for specific purposes
Manufacturing products
Construction
To separate mixtures
Filtration – separates materials based on size of particles
Heterogeneous (Suspensions)
Distillation – separates substances in solution using boiling points
Homogeneous (Solutions)
2.3 Chemical Properties
Chemical property – describes a substance’s ability to change composition (new
substance)
Flammability – ability to burn
Reactivity – ability to combine chemically with other substances
Example: rust, tarnish
Recognizing Chemical Changes
3 types of evidence
Change in Color
Ripening banana
Production of a Gas
Vinegar and baking soda
Formation of a Precipitate
Lemon juice and milk - curdling
Chemical or Physical Change?
Chemical – composition of
matter changes – forms
new substance
Physical – composition of matter stays the same