I. The three states of matter
- a state of matter in which the component particles are in contact with each
other; a solid has a definite volume and definite shape
Gas - a substance that has no definite shape or volume ; the particles in a gas are far apart because there is little or no attraction between them.
- the gaseous state of a substance that normally exists as a solid or liquid
at room temperature.
II. Pure component or mixture?
Mixtures are a combination of different substances (elements and compounds)
Kinds of mixtures
1. Homogeneous - completely uniform,
components equally distributed, "solutions" - salt water, vodka, syrup
III. Separating Mixtures - Lots of ways, each based on exploiting differences in properties - here are a few examples
1. Size - separating gold - use sieve
2. Density - separating gold - "pan"
3. Magnetic character - Demo: Iron (magnetic) from corn flakes
4. Boiling point - common way to separate liquids
IV. Pure substances - (obtained after complete separation)
a. uniform properties
b. definite composition
can't be further separated
Types of pure substances
1. Element - a substance that cannot be broken down into simpler substances by chemical means (tabulated in the periodic table, carbon, silicon, gold, etc...). Made up entirely of atoms of the same "type"
2. Compound - substance formed by a chemical combination of one or more elements in which component elements are in a fixed whole number ratio. Compounds consists of atoms of different elements chemically bound together. Can be decomposed into other elements or compounds by a chemical process.
pure substance vs. mixture
Summary - FIGURE 1.2 - The Classification of Matter
V. Properties of Matter
1. Physical properties - the property of a
substance that can be measured without changing the composition of the
Physical or Chemical property?
What color is it? PP
VI. Physical or Chemical Changes
Physical change - conversion that does not change the substance composition - tends to be reversible
Chemical change - change in composition of matter
reactant --> product
Back to our iron and sulfur example
Can heat the mixture and make the compound pyrite
iron + sulfur -> iron sulfide (one for of which is pyrite)
Identifying a chemical change vs. physical change can be difficult
Some signs of a chemical change
1. change in a property
a. color change - e.g. copper patina
copper + oxygen + water + carbon dioxide -> "basic copper carbonate (pale green)"
b. odor change - e.g. rotting fish
primary smell comes from molecules belonging to a class of compounds know as amines, two particular amines are aptly named putrescine (1,4 diaminobutane) and cadaverine (1,5 diaminopentane, NH2(CH2)5NH2). An amine you are likely familiar with is household ammonia (solution of ammonia in water).
c. change in magnetic properties (pyrite example above)
2. Change in physical state at a given temperature (forming a gas from a solid as in the air bag example above)
always have to be careful though, these are not absolute
e.g. The smell (and loss of it) from a "scratch and sniff" is not due to a chemical change. Evaporation of an odiferous substance.