- Chemistry: The study of properties of materials and the changes the materials undergo
- Matter- Anything that occupies space and has mass. We can classify it based on:
- The State of Matter: Solid, Liquid, or Gas
- Solids and liquids are referred to as the condensed phases.
- Gases have different characteristics than the latter.
- What state a material is in depends largely on two factors:
- The amount of kinetic energy the particles possess
- The strength of attraction between the particles, potential energy (inter molecular forces)
- A change in state is a physical change where the physical form changes but keeps its composition.
- Reversible by changing the temperature.
- Solids:
- High potential energy and low kinetic energy.
- The only motion is vibration of the atoms and molecules.
- Definite shape and volume.
- Liquids:
- Attraction between atoms is still high but it has higher kinetic energy and lower potential energy
- definite volume but not definite shape for it takes up the shape of the container.
- Vibration, rotation, and some translation
- Gas:
- There is little attraction between the atoms
- High kinetic energy, low potential energy
- Vibration, rotation, and lots of translation
- The Composition of Matter:
- Matter is either a mixture or substance.
- Substance: form of matter with definite composition and distinct properties.
- Elements: A pure substance that cannot be chemically converted into a simpler substance. Consists of Atoms or Elements.
- Atoms: Any no diatomic elements; Atoms are the building blocks of matter and they combine to make molecules.
- Molecule: Any Diatomic element (elements that only occur in pairs in nature)
- Br2, I2, N2, Cl2, H2, O2, F2
- A chemical combination of two or more atoms
- Compounds: elements can combine with other elements to form compounds
- Mixture: physical combination of two or more substances.
- homogeneous: uniform throughout
- heterogeneous: NOT uniform throughout
- Physical Change:
- A change that occurs without changing the molecular composition. The same element is present before and after.
- Ex. Water is the same no matter if it is liquid or solid (ice).
- Examples of physical properties:
- Mass, volume, color, solid, texture, smell, taste, ect.
- Extensive Properties: Properties that depend of the amount of a substance (mass, volume)
- Intensive Properties: Does not change with the amount of a material (density, specific heat, melting and boiling points)
- Chemical Change:
- The property's potential to undergo change to form a different product.
- Results of a bonds breaking in the reactants and rearrangements of the atoms to different substances (s).
- Combustible, corrosive, toxic, flammable
- indicated by temp., color, bubble and precipitate formation
- The Atomic Theory of Matter
- Define Laws of Chemistry:
- Law of Mass Conservation: In a chemical reaction, matter is neither created not destroyed.
- The combined masses of the reactant must equal combined masses of the product
- Law of Definite Proportions/ Law of Definite Composition:
- All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements.
- Laws of Multiple Proportions (John Dalton):
- The ratio of the two masses is a small whole number
- John Dalton's Atomic Theory:
- Each element is composed of elements
- Each element is composed of only one type of atom
- Compounds are formed when atoms of more than one element combine in simple, whole number rations (ex. H2O)
- Atoms of an element are not changed into atoms of different element by chemical reactions
- John Dalton:
- Modern atomic theory
The Discovery of the Electron:
- JJ
Thomson: Discovered the Electon
- Cathode
Ray Tubes: A high voltage passed through a partially evacuated glass tube,
produced radiation
Robert Millikan Experiment:
- Oil
drop experiment
- Find
out charge of electron (1.6X10^-19)
The Discovery of Atomic Nucleus:
- Ernest
Rutherford: Gold Foil Experiment; discovered the mystery of how electrons fit inside the atom
- Used
beams of particles as projectiles to explore the structure matter
- Discovered nucleus and it is contents: protons and neutrons.
- Atoms are composed of three subatomic particles: protons, neutrons, and electrons that effect the chemical behavior of an atom.
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| Protons and neutrons reside in the nucleus of the atom (held together by strong nuclear force) while the area surrounding the nucleus is a diffused region of negative charge where the electrons reside. |
- An atom must have the correct ratio of protons and neutrons for stability.
- Protons: The number of protons in the nucleus in the nucleus is called the atomic number (Z) and determines the identity of the atom
- Neutrons: neutral
- Electrons: Same number as protons
