• anything thast occupies space and has mass
• matter can be continually divided without losing its distinct properperties

what is an atom

1. pure substances: into elements and compounds
2. mixtures: into homogeneous and heterogeneous mixtures

only if all the units that make up the matter are all the same

• Pure substance (a substance) has to have uniform(definitly fixed) chemical composition and it is also homogeneous
• water, table salt, and gold are pure substances
• a substance cannot be seperated into 2 or more component substances by physical means such as breaking, melting, boiling, or dissolving 

1. a blend of two or more substances
2. salt or sugar solution is an example of a mixture
3. each substance in a mixture retains its chemical identity
4. mixtures are not pure substances and does not have a definite composition
5. salt solutions are mixtures that have different compositions

What is a homogeneous mixture?

• it contains substances that are not visibly distinguishable

• a homogeneous mixture is also called a solution \
• substances in a mixture are uniformly distributed thorughout the mixture

• it contains substances that are visbily distinguishable
• a mixture of sand with fragmetns of iron is a heterogeneous mixture

• it lists the symbols of the 114 known elements in a tabular format.

• the periodic table is divided into groups and periods
• group=vertical column in the table
• elements in the same group have similar chemical properties
• a group is also called a family
• period=horizontal row in the table

• metals=have the capacity to conduct electricity whereas nometals do not
• metals are lustrous and malleable wheras nonmetals are not
• metalloid=elements located in between the metal and nonmetals
• metalloid is a semimetal
• metalloid has both metallic  and nonmetallic properties

• Group 1A=contains Alkali metals=lithium(Li), sodium(Na), potassium(K), rubidium(Rb), cesium(Cs) and francium(Fr)
• hydrogen is a nonmetal not an alkali metal
• alkali metals are very reactive, do not occure in nature
• Group 2A=contrains the alkaline earth metal=beryllium(Be), magnesium(Mg), calcium(Ca), strontium(Sr), barium(Ba), and radium(Ra)
• alkaline metals are less reactive than alkali metalas
• Group 7A=contains the halogens=fluorin(F), chlorine(Cl), bromine(Br), iodine(I), and astatine(At)
• Halogens are all nonmetals and do not occure in nature in pure forms but only combined forms with other elements

uses element symbols and integer numbers in subscript if the compound has more than one atom of an element

H2O

H=symbol for hydrogen

2=subscript 2 indicates two H atoms

O=no subscript number here indicates one O atom

1. an element is made of identical atoms
2. an atom is the smallest particle of an element
3. an atom retains all the chemical properties of the element
4. when using element=referring to a single atom or many identical atoms that are bonded or connected to each other

Compound vs Molecule

1. molecule=an aggregate of 2 or more atoms held tightely together
2. Diatomic element=a molecule that contains 2 atoms of the smae element
3. compound=contains atoms of different elements

SEVEN

• H2, N2, O2, F2, Cl2, Br2, and I2
• during normal conditions, the seven diatomic molecules do not occur as individual atoms but as molecules
• triatomic element=ozone molecule(formula O3)

sulfur is one example

• sulfur contains 8 sulfur atoms (formula S8)
• most elements exist as polyatomic elements
• monatomic element=an element consisting of only a single atom
• Helium(He), neon(Ne), and argon(Ar) are examles of monatomic element

`matter can exist as:

• gas
• liquid
• solid

The key factor that differentiates each state(states of matter) from the others is the distance between the molecules

1. gas=molecules are far apart from each other and move very fast
2. liquid=the molecules are packed closely together but still move reasonabley fast, allowing liquids to pour
3. solid=the molecultes are held together very tightely causing solids to have fixed shapes

• no change occurs in the identies of substances
• examples=melting ice and vamporizing liquid water are physcial change because the substance water=unchanged

• a change in the identities of substances
• example=buring wood=causes a chemical change=burining converts wood and oxygen gas(O2) to carbon dioxide(CO2) and water vapor(H20)

the total mass of all the substances before and after the change remains the same

• if 5.0g of water is completely converted to hydrogen gas and oxygen gas, the total mass of the two gases must also equal 5.0g

any property that does not involve change in the identity of the substance

• properties of a substance=melting point, boiling point, color, density, and physical state(solid, liquid, gas)--these do not involve a chemical change

Any property of a substance that involves a change in the identity of the substance

• example of chemical property=chemical reactivity
• sodium is so reactive that even a tiny amount of sodium reacts violently with water
• strong reactivity, lack of reactivity, or any degree of reactivity of a substance is an example of its chemical properties

what is energy?

what is chemical energy?

what is thermal energy?

what is exothermic?

what is endothermic?

commonly defined as the capacity to do work

• changes in matter involve changes in energy
• change takes place through the interaction between between matter and energy
• chemical energy=energy stored in the structure of a compound
• thermal energy=energy expressed as heat
• exothermic=chemical and physical changes that result in a release of heat energy
• endothermic=changes that result in an absorption of energy

what is kinetic energy? 

What is Potential energy?

• Kinetic Energy=energy generated by a moving object=it is the energy of motion
• Potential Energy=is stored energy
• Potential energy is converted to kinetic energy as an object changes its position

Energy cannot be created or destroyed. It can only be converted from one form to another

• energy is conserved