Chapter 2: Chemistry Basics Flashcards
What is the difference between chemical change and physical change?
A chemical change results in the formation of a new chemical substance. Example: element -> compound
A physical change changes the state of a substance, but it is still the same substance.
Example: ice -> water
What is the difference between the chemical and physical properties of matter?
Chemical properties describe the chemical changes that a sample undergoes.
Ex. Flammability
Physical properties can be observed without changing the chemical nature of the sample.
Ex. mass, volume, color, odor, density, melting point
Example: WATER PROPERTIES
Chemical: Water can be decomposed into l part oxygen and 2 parts hydrogen, water is the product of metabolizing food, and so forth.
Physical: Density is 1.0 g/mL, clear and colorless etc.
What is matter?
Matter is anything that occupies space and has mass; doesn’t have to be visible (ex. air and nitrous oxide).
Atoms are the basic building blocks of matter.
What is an atom comprised of?
Protons (mass ~1 amu, charge +1)
Neutrons (mass ~1 amu, charge 0)
Electrons (mass 0, charge -1)
What are molecular and empirical formulas?
Molecular formulas: gives the number of each type of atom in a molecule
Empirical formula: gives the lowest whole number ratio of atoms in a molecule
Example: Benzene
Empirical: C1H1
Molecular: C6H6
What are ionic compounds and how do they react in water?
Ionic compounds consist of anions and cations.
They are not molecules because every anion is attracted to every cation, so none of the ions are bound into a discrete unit.
Ions dissociate in water, transport of ions through solution causes flow of current.
Ionic compounds that dissolve in water are strong electrolytes. Electrolytes are compounds that dissolve in water to give a solution that conducts electricity.
Define and describe molecules, atoms, compounds and mixtures.
Atom: fundamental building block of all matter
Molecules: aggregates of atoms chemically bonded into a discrete unit
ex. O2, N2, O3
Compounds: two or more kinds of atoms
ex: CO2, H20
Mixtures: aggregates of two or more pure substances that can be separated via physical means
How is the periodic table organized?
The modern periodic table organizes elements by increasing atomic number.
Rows = periods; represent electron energy shells
Columns = groups/family; elements in a given family have similar chemical and physical properties. Most elements are solid at room temp and pressure. Mercury and bromine are the only two liquids at room temp.
Nonmetals: right hand side
Metals: left side through the center
What are characteristics of metals?
Metals will LOSE electrons when reacting with non-metals.
Almost always solids and tend to form cations.
Malleable, ductile, shiny, good conductors of both heat and electricity.
What are characteristics of Non-metals?
Tend to gain electrons when reaction with metals/form anions.
May be solids, liquids or gases.
Nonconductors of heat and electricity, brittle, dull, low density.
What is atomic number? Mass?
Atomic number (Z): # of protons in nucleus
Mass number (A): atomic # + neutron #; can never be smaller than atomic number
Amu is the unit of mass
What is an ion, cation, anion? How do ions form?
Ion: atom or group of atoms with a net electrical charge
Anions: negatively charged ions that are formed by the addition of electrons
Cations: positively charged ions formed by the loss of electrons
How do you decide whether a compound is a molecular or ionic?
Ionic compounds generally consist of metal and one or more nonmetals
Molecular compounds: only nonmetals
Example: Glucose C6H12O6 is a molecular compound as it only contains nonmetals
Describe periodic table trends in atomic radius?
Moving across = atomic radius decreases
Moving down = atomic radius increases
Is there a trend on the periodic table about which kind of ion an element is likely to form?
Metals (left side of the table) tend to form cations
Nonmetals (right side) tend to form anions
