Unit 1 Flashcards
Chemical change
When the chemical composition of a substance is altered and results in new substances being formed
Chemical reaction
The conversion of two or more elements to a chemical compund
Compound
Contains two or more elements and has chemical and physical properties that are usually different from those of the elements of which it is composed.
Distillation
Physical process of converting homogenous mixtures
The mixture is boiled, and the most volatile substance is boiled first, and then it is condensed back into a liquid in the recieving flask, while the less volatile component remains in the distillation flask
Electrolysis
Process of using electricity to separate water into hydrogen and oxygen
Elements
substance that cannot be broken down into simpler ones by chemical changes
Experiments
Systematic observations or measurments, usually under controlled conditions in which a single variable changes.
Enables scientist to determine whether the hypothesis is valid, incorrect or must be modified
Filtration
Method of separating heterogenous mixtures, where the mixture is passed through barrier, with holes or pores smaller than the solid particles.
Gases characteristics
Have neither fixed shapes or volumes and expand to fill their container
Heterogenous mixtures
When composition of a material is not completely uniform, or their component parts cannot be easily separated.
Homogenous (or solutions)
Materials that are in the same state, have no visible boundries, and are uniform throughout.
Ex. air and tap water
How are homogenous mixtures separated?
Through physical processes called distillation and crystallization
How can kinetic energy of a substance be changed?
Through heating and cooling, which can change the physical state of a substance
Hypothesis
Educated guess that puts scientist’s understanding of the topic into a form that can be tested
Intermolecular forces
Attractive forces that try to draw particles in
John Dalton’s atomic theory
Fundamental concept that states all elements are composed of atoms
Postulates of the theory was
1. All matter is composed of extremely small particles called atoms.
2. Atoms of a given element are identical in size, mass, and other properties.
3. Atoms of different elements differ in size, mass, and other properties.
4. Atoms cannot be subdivided, created, or destroyed.
5. Atoms of different elements can combine in simple whole number ratios to form chemical compounds.
6. In chemical reactions, atoms are combined, separated, or rearranged.
Kinetic energy
Function of substance temperature that keeps molecules apart and moving around
Law
Verbal or mathematical description of phenomenon that says what happens but not why it happens
Allows for general predictions
Law of Conservation
States that in a chemical reaction, matter is neither created, nor destroyed but remains constant in the system
Total mass of reactants = Total mass of products
Law of definite proportions
a given chemical compound always contains its component elements in fixed ratio (by mass) and does not depend on its source and method of preparation.
Applies when elements are reacted together to form the same product, thus can be used to compare to experiments where elements react to form the same compound.
Laws of chemical combination
Foundational laws that describe how substances react
- Law of Conservation of Mass
- Law of Definite Proportions
- Law of Multiple Proportions
Liquid characteristics
have fixed volumes but flow to assume the shape of their containers
Physical change
Process of matter changing from one physical state to another
Pressure
Amount of force exerted on a given area
Pure chemical substance
Any matter that has a fixed chemical composition and characteristic properties
ex. Oxygen since it is a pure colorless, oderless gas at 25 C
Qualitative observations
Describe properties or occurances in ways that do not rely on numbers
ex: table salt is a crystalline solid, sulfur crystals are yellow
Scientific method
How scientists search for answers to questions and solutions to problems
- Making observations
- Formulating hypothesis
- Designing experiments
Solid characteristics
Relatively rigid and have fixed shapes and volumes
Theory
Thought-out explanation of the natural world, constructed using the scientific method
Three common states of matter
Solid, liquid and gas
What can most mixtures be broken down into?
Pure substances, which could be either elements or compounds
What does the state of a substance depend on?
The balance between kinetic energy of individual particles and intermolecular forces
What is the volume of gases dependent on?
Temperature and pressure
What would affect intermolecular forces?
Increasing the pressure on a substance would force molecules closer together, thus increasing IM forces
Electrostatic forces
The electric charge two objects exert on each other
What is the magnitude of the force dependent on?
It is linearly proportional to the distance between the two objects
Inversely proportional to the square distance between each other
Elementary charge
Charge of electron and donated by e
Fundamental physical constant that is 1.602176634× 10^−19 C
Electron
Negatively charged sub-atomic particle that is either bound to an atom or free
Thompson’s Non-nuclear model
Thomson’s model that electrons were embedded in a uniform sphere that contained both the positive charge and most of the mass in an atom.
Was created around the conclusion that atoms must have positive charges to balance the negative ones.
Ernest Rutherford experiments
Passed a beam of alpha positive particles through a gold foil that contained atoms.
Concluded most atom was empty space since many particles went straight through
Concluded a very dense positive charged nucleus since some particles were deflected
Protons
Positively charged particles
Properties of subatomic particles
- Electrions have electrical charges identical in magnitude but opposite in sign. Charge of proton is +1 and charge of electron is -1
- Neutrons have approximately the same mass as protons but no charge, electrically neutral
- The mass of a proton or a neutral is about 1836 times greater than the mass of an electron. Protons and neutrons make a bulk of the atom mass
Structure of atom
Almost all atom mass contained in tiny dense nucleus that carries a positive electric charge.
Almost all atom volume consists of empty space where electrons reside
Strong nuclear forces
Electrostatic repulsions between negatively charged electrons would cause the electrons to be uniformly distributed
throughout the atom’s volume.
Stronger than electrostatic interactions and holds the nucleus together
Atomic number (Z)
Defining trait of element that determines identity
Number of protons in nucleus of atom
Also indicates number of electrons in a neutral atom
Mass number (A)
Total # of protons and neutrons in an atom
How to find the number of neutrons
Find difference between mass number and atomic number
A - Z = # of neutrons
Periodic table
Table of known elements arranged in order of increasing Z
What is the chemistry of each elements determined by?
Their # of protons and electrons
Isotopes
Elements that have the same number of protons but different numbers of neutrons
All isotopes exhibit the same chemistry and only differ in mass number
Ion
Atoms that contain different number of protons and neutrons
Electrically charged and is defined by its atomic charge
Atomic charge = # of protons - # of electrons
Atomic mass
Weighted average mass of all naturally occurring isotopes of the element
How are the relative masses of atoms reported?
Atomic mass unit (amu)
