Summary Pg 25-34, 36-39

2-1 What You Know About Matter

-Identify matter and distinguish one kind from another: different look, taste, densities, colors, boiling points.

2-2 Purifying Matter

1. Mixture - two or more kinds of matter that have separate identities

2. Solutions - mixtures like salt water or sugar water that look uniform throughout and do not scatter light

3. Mixtures are matters that can be separated into component parts and have different identities.

4. Distillation - solutions can be separated into component parts by boiling.

6. Matter can be separated into mixtures and pure substances.

2-3 Characteristics of Pure Substances

- Pure substances have a constant boiling point, mixtures do not.

- The difference between pure substances and mixtures is solidify

- The similar differences between mixtures and pure is freeze

- Freezing point: temperature at which liquid change to solid

- Melting point: temperature at which solid change to liquid

2-4 Chemical and Physical Changes

- Density: a property of matter that describes its mass per unit volume
- Chemical changes: changes that produce a new kind of matter with different properties.
  Decomposition is one type of chemical change. One kind of matter comes apart to form two or 
  more kidns of matter during decomposition.
- Melting: the change of a solid to a liquid without the formation of any new kidn of matter
- Physical changes: changes that are easily reversed to get the original material back again, 
  and do not produce new substances.
Ex. boiling


2-5 Compounds and Elements

- Electrical conductivity tester is used to test electrical conductivity. If the two wires are connected by a piece of metal or any other matter that conducts electricity, the light bulb will glow because electricity will flow through.
- Electrolysis involves passing an electric current through a substance, causing it to decompose into new kinds of matter.
- The electrolysis of sodium chloride and water are chemical changes.


Differences between decomposition and distillation:
Decomposition
- a single, pure substance is changed into new substances with different properties
- chemical change


Distillation
- the separated components exist in the original mixture as separate substances
- physical change

2-6 Compounds Have a Definite Composition

- Law of definite composition: the compounds of elements always have a definite composition.

Ex. The definite composition of water was described in terms of volume: The volume of hydrogen gas obtained from water is always twice the volume of oxygen gas obtained.

- Law of multiple proportions: two or more compounds with different proportions of the same elements can be made.

- Any sample of a given compound contains the same percentage by mass of each element. Samples of compounds which contain the same elements but in different percentages by mass are different.

2-7 Matter Is Made Of Atoms

- Macroscopic observations: observations of an experiment that are large enough to be visible to the naked eye

- Macroscopic properties: melting point, boiling point, heat of fusion, temperature, mass

- Mixture differs from a pure substance: A pure substance has a definite boiling point, a mixture does not. A mixture can be broken down, but a pure substance cannot.

- Explain: a word that talks about the things as they might be.

- Scientific explanation: off a way to observe why things happen (can be intelligent guesses that are based on observation)

- Microscopic models are too small to be seen except under a microscope. When used with SI units, means one millionth) and use to explain the behavior of matter.

- Matter is composed of some kind of small pieces-atoms, molecules

- Atoms: the smallest component of an element which have the chemical properties of the element.

- Atoms are represented with spheres of various sizes and colors

- Size of atoms: the relative size of the actual atom, but not the representations of real atoms

- Elements are pure substances and cannot be broken down.

(If each element has different kind of atoms, there are 109 atoms because there are 109 elements)

1-109: atomic numbers

Solid: atoms are stuck together

Liquid: atoms are still close together, but also can move past one another

Gas: atoms are far apart, moving in a straight line until they collide with other gas atoms or the wills of container)

As temperature increases, atoms in solid vibrate move. Heat is absorbed to overcome the forces of attraction that hold the particles together.

The force of gravity pulls the atoms down, so the liquid flow to take the shape of its container.

Temperature of a liquid is raised to its boiling point. Then kinetic energy increases, and atoms move faster. They eventually escape from the liquid to move farther apart and become gas.

Molecules: particles made of more than one atom

(Some elements exist in various combinations of their atoms forming molecules.)

Compound: a substance formed by chemical union of two or more elements in definite proportion. (Because elements contain only one kind of atom, so compounds are made of two or more kind of atoms.)

When a compound decomposes, the different atoms are separated (need enough energy-heat, electricity)

Compounds: solids, liquids, gases

If the atoms within a water molecule came apart, new substances are formed (hydrogen and oxygen) with new properties

Molecules can separate, atoms cannot. More energy is required to break the bonds which hold atoms together in a molecule.

Ions: particles that have an electrical charge

The only way to know which compound are ionic (melt to form ions)and which compounds are molecular(melt as molecules)is to check them for conductivity.