Classification of Matter
Define a pure substance
A substance with a uniform and unchanging composition, such as an element or a compound.
What family does chlorine belong to?
Halogens.
Who proposed the “plum pudding” model?
J.J. Thomson.
What type of reaction is this: NH3 + HCl → NH4Cl?
Formation.
Balance this equation: ___ Li + ___ H2O → ___ LiOH + ___ H2.
2Li + 2H2O → 2LiOH + H2.
What is the molar mass of Hg (mercury)?
200.59 g/mol.
What is the difference between an element and a compound?
An element is made of only one type of atom, while a compound is made of two or more types of atoms chemically combined.
Name one property of noble gases.
Noble gases are non-reactive under normal conditions.
Which atomic model introduced the idea of energy levels?
Bohr’s atomic model.
Classify the following reaction: Fe + O2 → Fe2O3.
Formation.
Balance this equation: ___ C6H6 + ___ O2 → ___ CO2 + ___ H2O.
C6H6 + 15/2O2 → 6CO2 + 3H2O (or 2C6H6 + 15O2 → 12CO2 + 6H2O).
Calculate the molar mass of NH3 (ammonia).
17.03 g/mol.
Classify the following as heterogeneous or homogeneous: blood, cement.
Blood: Heterogeneous; Cement: Heterogeneous.
What is the IUPAC symbol and atomic number of potassium?
Symbol: K; Atomic Number: 19.
How many electrons can fit in the second orbital?
8 electrons.
What is the difference between a single replacement and a double replacement reaction?
Single replacement: One element replaces another. Double replacement: Two compounds exchange ions to form new compounds.
Balance this equation: ___ Pb2O4 + ___ HCl → ___ PbCl2 + ___ Cl2 + ___ H2O.
Pb2O4 + 4HCl → 2PbCl2 + Cl2 + 2H2O.
Determine the molar mass of Ca(NO3)2 (calcium nitrate).
164.10 g/mol.
Identify whether this is a physical (P) or chemical (C) change: a car rusts.
Chemical (C).
Describe the difference between alkali metals and alkaline-earth metals.
Alkali metals (Group 1) are highly reactive, soft metals. Alkaline-earth metals (Group 2) are less reactive and harder.
Explain the charge and location of a neutron in an atom.
Neutrons have no charge (neutral) and are located in the nucleus.
What kind of reaction is this: C4H12 + O2 → H2O + CO2?
Combustion.
Why must chemical equations be balanced?
To satisfy the law of conservation of mass, which states that matter cannot be created or destroyed.
What is the molar mass of glucose (C6H12O6)?
180.16 g/mol.
What is the difference between atoms and molecules?
Atoms are the smallest units of an element, while molecules are formed when two or more atoms bond together chemically.
Identify whether iodine is a metal, nonmetal, or metalloid and state its family name.
Iodine is a nonmetal and belongs to the halogens family.
Draw an atom of sodium. How does the diagram change for a sodium ion with a +1 charge?
Sodium atom: 11 protons, 12 neutrons in the nucleus; 11 electrons in 3 orbitals. Sodium ion (Na+): Loses one electron, leaving 10 electrons in 2 orbitals.
Balance this equation: ___ N2 + ___ H2 → ___ NH3.
N2 + 3H2 → 2NH3.
Balance this equation: ___ P2H4 → ___ PH3 + ___ P4.
2P2H4 → 4PH3 + P4.
Calculate the molar mass of Pb(NO3)2 (lead nitrate).
331.21 g/mol.
Classify coffee and Pepsi as homogeneous or heterogeneous.
Coffee: Homogeneous; Pepsi: Homogeneous.
Name one transition metal and its use.
Iron (Fe): Used in construction and manufacturing steel.
Summarize the Rutherford planetary model.
Rutherford proposed that atoms have a dense nucleus surrounded by orbiting electrons, similar to a solar system.
Classify this reaction: Mg3(PO4)2 + H2 → Mg + H3PO4.
Single replacement.
Balance: ___ C3H8 + ___ O2 → ___ CO2 + ___ H2O.
C3H8 + 5O2 → 3CO2 + 4H2O.
What is the molar mass of HCl (hydrochloric acid)?
36.46 g/mol.
Differentiate between physical and chemical changes with an example for each.
Physical change: Ice melting (no new substance formed). Chemical change: Wood burning (new substances formed).
Which group contains elements that are brittle and non-conductive?
Nonmetals.
How many valence electrons does aluminum have?
3 valence electrons.
What happens in a decomposition reaction?
A compound breaks down into two or more simpler substances.
alance: ___ Cl2 + ___ NaBr → ___ NaCl + ___ Br2.
Cl2 + 2NaBr → 2NaCl + Br2.
Find the molar mass of C3H6O (acetone).
58.08 g/mol.
Classify matter as either a mixture or a pure substance: saltwater, gold.
Saltwater: Mixture; Gold: Pure substance.
Why are metalloids unique on the periodic table?
They have properties of both metals and nonmetals.
What is the electron configuration for oxygen?
1s² 2s² 2p⁴.
What is a precipitate, and in which type of reaction does it commonly form?
A precipitate is a solid formed during a chemical reaction, commonly in double replacement reactions.
Balance: ___ N2 + ___ O2 → ___ NO2.
N2 + 2O2 → 2NO2.
Calculate the molar mass of CH4 (methane).
16.04 g/mol.