Sample Chemistry Curriculum : ChemQuiz.net

This is a suggested chronological order for completing practice quizzes on ChemQuiz.net that should match up with most introductory high school or college Chemistry classes. Each practice quiz has 10 questions or items and a passing threshold of 8 correct responses. Just click the red Preview button to get started!

Here are all of the practice quizzes in suggested order:

Here are the practice quizzes with suggested settings:

Quiz Name	Settings	Preview
SI Conversions	Quiz type: One-step conversions (convert to & from base units, easier) Prefix types: Common prefixes only (k, d, c, m) Units: Common chemistry units only (g, m, L, J, Pa)
SI Conversions	Quiz type: Two-step conversions (convert to & from units with prefixes, more challenging) Prefix types: Common prefixes only (k, d, c, m) Units: Common chemistry units only (g, m, L, J, Pa)
SI Conversions	Quiz type: Both Prefix types: More prefixes (G, M, k, h, D, d, c, m, µ, n) Units: Common chemistry units only (g, m, L, J, Pa)
Significant Figures	Type of questions: Counting sig figs in numbers Display numbers as: Decimal (regular) notation, Scientific (exponential) notation
Significant Figures	Type of questions: Multiplication & division problems with sig figs Display numbers as: Decimal (regular) notation
Significant Figures	Type of questions: Addition & subtraction problems with sig figs Display numbers as: Decimal (regular) notation
Percent Error & Percent Yield	Problem types: Percent error, Percent yield Display problems as: List of givens and wanted (easier)
Percent Error & Percent Yield	Problem types: Percent error, Percent yield Display problems as: Word problems (more challenging)
Density Calculations	Density units to use: Grams per cubic centimeter (g/cm³) and grams per milliliter (g/mL) Display problems as: List of givens and wanted (easier)
Density Calculations	Density units to use: Kilograms per cubic meter (kg/m³) Display problems as: List of givens and wanted (easier)
Density Calculations	Density units to use: Grams per cubic centimeter (g/cm³) and grams per milliliter (g/mL), Kilograms per cubic meter (kg/m³), specific gravity Display problems as: Word problems (more challenging)
Electron Configuration	Type of problems: Determine electron configuration from element Element groups to use (select at least one): s-block (alkali metals and alkaline earth metals), p-block (nonmetals, metalloids and other metals) Use element names or symbols: Mix & match (both names and symbols) Use noble gas shortcut: No, do not allow use of noble gas shortcut
Electron Configuration	Type of problems: Determine electron configuration from element, Determine element from electron configuration, Determine number of electrons in an element's orbital Element groups to use (select at least one): s-block (alkali metals and alkaline earth metals), p-block (nonmetals, metalloids and other metals), d-block (transition metals) Use element names or symbols: Mix & match (both names and symbols) Use noble gas shortcut: Yes, allow use of noble gas shortcut
Naming Compounds & Calculating Molar Masses	Quiz type: Names & formulas Compound types: Start with names or formulas: Chemical formulas
Naming Compounds & Calculating Molar Masses	Quiz type: Names & formulas Compound types: Start with names or formulas: Chemical names
Naming Compounds & Calculating Molar Masses	Quiz type: Names & formulas Compound types: Ionic compounds with polyatomic ions (more challenging) Start with names or formulas: Chemical formulas
Naming Compounds & Calculating Molar Masses	Quiz type: Names & formulas Compound types: Ionic compounds with polyatomic ions (more challenging) Start with names or formulas: Chemical names
Naming Compounds & Calculating Molar Masses	Quiz type: Names & formulas Compound types: Molecular compounds Start with names or formulas: Mix & match (both formulas and names)
Naming Compounds & Calculating Molar Masses	Quiz type: Molar mass (aka formula weight) Compound types: Start with names or formulas: Chemical names
Naming Compounds & Calculating Molar Masses	Quiz type: Molar mass (aka formula weight) Compound types: Ionic compounds with polyatomic ions (more challenging) Start with names or formulas: Chemical names
Naming Compounds & Calculating Molar Masses	Quiz type: Molar mass (aka formula weight) Compound types: , Ionic compounds with polyatomic ions (more challenging), Molecular compounds Start with names or formulas: Chemical formulas
Mass Ratios & Percent Composition	Type of problems: Mass ratios Chemical compound types: Ionic compounds with monatomic ions (easier), Molecular compounds Chemical names or formulas: I want formulas only (easier)
Mass Ratios & Percent Composition	Type of problems: Mass ratios Chemical compound types: Acids, Ionic compounds with polyatomic ions (more difficult) Chemical names or formulas: I want formulas only (easier)
Mass Ratios & Percent Composition	Type of problems: Mass ratios Chemical compound types: Acids, Ionic compounds with monatomic ions (easier), Ionic compounds with polyatomic ions (more difficult), Molecular compounds Chemical names or formulas: I want names only (more difficult)
Mass Ratios & Percent Composition	Type of problems: Percent Composition Chemical compound types: Ionic compounds with monatomic ions (easier), Molecular compounds Chemical names or formulas: I want formulas only (easier)
Mass Ratios & Percent Composition	Type of problems: Percent Composition Chemical compound types: Acids, Ionic compounds with polyatomic ions (more difficult) Chemical names or formulas: I want formulas only (easier)
Mass Ratios & Percent Composition	Type of problems: Percent Composition Chemical compound types: Acids, Ionic compounds with monatomic ions (easier), Ionic compounds with polyatomic ions (more difficult), Molecular compounds Chemical names or formulas: I want names only (more difficult)
Balancing, Identifying & Predicting Chemical Equations	Quiz type: Identifying chemical reactions Reaction types to include: Combination, Combustion, Decomposition, Double replacement, Single replacement Equation difficulty: Easy, Moderate, Challenging
Balancing, Identifying & Predicting Chemical Equations	Quiz type: Balancing chemical equations Reaction types to include: Combination, Combustion, Decomposition, Double replacement, Single replacement Equation difficulty: Easy, Moderate
Balancing, Identifying & Predicting Chemical Equations	Quiz type: Balancing chemical equations, Identifying chemical reactions Reaction types to include: Combination, Combustion, Decomposition, Double replacement, Single replacement Equation difficulty: Easy, Moderate, Challenging
Balancing, Identifying & Predicting Chemical Equations	Quiz type: Predicting chemical reactions Reaction types to include: Combination, Combustion, Decomposition, Double replacement, Single replacement Equation difficulty: Easy, Moderate, Challenging
Balancing, Identifying & Predicting Chemical Equations	Quiz type: Predicting chemical reactions Reaction types to include: Acid-Base Neutralization Equation difficulty: Easy, Moderate, Challenging
Balancing, Identifying & Predicting Chemical Equations	Quiz type: Identifying chemical reactions, Predicting chemical reactions Reaction types to include: Combination, Combustion, Decomposition, Double replacement, Single replacement Equation difficulty: Easy, Moderate, Challenging
Balancing, Identifying & Predicting Chemical Equations	Quiz type: Balancing chemical equations, Identifying chemical reactions, Predicting chemical reactions Reaction types to include: Combination, Combustion, Decomposition, Double replacement, Single replacement Equation difficulty: Easy, Moderate, Challenging
Molar Conversions	Quiz type: Units to use (select at least one): grams Compound types: Acids, Elements, Ionic compounds with monatomic ions (easier), Ionic compounds with polyatomic ions (more difficult), Molecular compounds Display problems as: List of given and wanted values (easier) Use chemical formulas or names: Chemical formulas
Molar Conversions	Quiz type: Units to use (select at least one): grams, Liters, particles (e.g. atoms/molecules/formula units) Compound types: Acids, Elements, Ionic compounds with monatomic ions (easier), Ionic compounds with polyatomic ions (more difficult), Molecular compounds Display problems as: List of given and wanted values (easier) Use chemical formulas or names: Chemical formulas
Molar Conversions	Quiz type: Units to use (select at least one): grams, Liters, particles (e.g. atoms/molecules/formula units) Compound types: Acids, Elements, Ionic compounds with monatomic ions (easier), Ionic compounds with polyatomic ions (more difficult), Molecular compounds Display problems as: Word problems (more challenging) Use chemical formulas or names: Mix & match (both formulas and names)
Molar Conversions	Quiz type: Two-step conversions (e.g., grams → moles → particles) Units to use (select at least one): grams, Liters, particles (e.g. atoms/molecules/formula units) Compound types: Acids, Elements, Ionic compounds with monatomic ions (easier), Ionic compounds with polyatomic ions (more difficult), Molecular compounds Display problems as: List of given and wanted values (easier) Use chemical formulas or names: Mix & match (both formulas and names) Given values are: Random (more realistic)
Stoichiometry	Chemical equations are: Balanced Type of problems: Simple stoichiometry only (one given, one wanted) Units to use (select at least one): grams Chemical formulas or names: Chemical formulas
Stoichiometry	Chemical equations are: Unbalanced Type of problems: Simple stoichiometry only (one given, one wanted) Units to use (select at least one): grams Chemical formulas or names: Chemical formulas
Stoichiometry	Chemical equations are: Unbalanced Type of problems: Simple stoichiometry only (one given, one wanted) Units to use (select at least one): grams Chemical formulas or names: Chemical names
Stoichiometry	Chemical equations are: Balanced Type of problems: Simple stoichiometry only (one given, one wanted) Units to use (select at least one): liters (at STP) Chemical formulas or names: Chemical formulas Given values are: Random (more realistic)
Stoichiometry	Chemical equations are: Unbalanced Type of problems: Simple stoichiometry only (one given, one wanted) Units to use (select at least one): grams, moles, particles (e.g., atoms/molecules/formula units) Chemical formulas or names: Chemical formulas
Stoichiometry	Chemical equations are: Balanced Type of problems: Simple stoichiometry only (one given, one wanted) Units to use (select at least one): grams, moles, particles (e.g., atoms/molecules/formula units), liters (at STP) Chemical formulas or names: Chemical formulas Percent yield: Include percent yield calculations in problems (very challenging!)
Stoichiometry	Chemical equations are: Balanced Type of problems: Limiting reagents only (two given reactants, one wanted product) Units to use (select at least one): grams Chemical formulas or names: Chemical formulas
Stoichiometry	Chemical equations are: Unbalanced Type of problems: Limiting reagents only (two given reactants, one wanted product) Units to use (select at least one): grams Chemical formulas or names: Mix & match (both formulas and names)
Stoichiometry	Chemical equations are: Unbalanced Type of problems: Limiting reagents only (two given reactants, one wanted product) Units to use (select at least one): grams Chemical formulas or names: Mix & match (both formulas and names) Percent yield: Include percent yield calculations in problems (very challenging!)
Stoichiometry	Chemical equations are: Unbalanced Type of problems: A mix of both simple stoichiometry and limiting reagent problems Units to use (select at least one): grams, moles, particles (e.g., atoms/molecules/formula units) Chemical formulas or names: Mix & match (both formulas and names)
Stoichiometry	Chemical equations are: Unbalanced Type of problems: A mix of both simple stoichiometry and limiting reagent problems Units to use (select at least one): grams, moles, particles (e.g., atoms/molecules/formula units), liters (at STP) Chemical formulas or names: Mix & match (both formulas and names) Percent yield: Include percent yield calculations in problems (very challenging!)
Gas Laws	Type of problems (select at least one: Boyle's Law (pressure & volume), Charles' Law (temperature & volume), Gay-Lussac's Law (pressure & temperature) Pressure units to use (select at least one): atmospheres (atm), kilopascals (kPa) Temperature units to use (select at least one): degrees Celsius (°C), kelvins (K) Volume units to use (select at least one): liters (L), milliliters (mL) Ideal gas law units to use (select at least one for ideal gas problems): moles Units before & after (does not apply to ideal gas problems): Before and after units are consistent within a problem (easier) Display problems as: List of givens and wanted (easier) Display gases as: Chemical formulas
Gas Laws	Type of problems (select at least one: Boyle's Law (pressure & volume), Charles' Law (temperature & volume), Gay-Lussac's Law (pressure & temperature) Pressure units to use (select at least one): atmospheres (atm), kilopascals (kPa) Temperature units to use (select at least one): degrees Celsius (°C), kelvins (K) Volume units to use (select at least one): liters (L), milliliters (mL) Ideal gas law units to use (select at least one for ideal gas problems): moles Units before & after (does not apply to ideal gas problems): Before and after units are consistent within a problem (easier) Display problems as: Word problems (more challenging) Display gases as: Chemical formulas
Gas Laws	Type of problems (select at least one: Boyle's Law (pressure & volume), Charles' Law (temperature & volume), Gay-Lussac's Law (pressure & temperature) Pressure units to use (select at least one): atmospheres (atm), kilopascals (kPa) Temperature units to use (select at least one): degrees Celsius (°C), kelvins (K) Volume units to use (select at least one): liters (L), milliliters (mL) Ideal gas law units to use (select at least one for ideal gas problems): moles Units before & after (does not apply to ideal gas problems): Before and after units are consistent within a problem (easier) Display problems as: Word problems (more challenging) Display gases as: Chemical names
Gas Laws	Type of problems (select at least one: Combined Gas Law (pressure, volume & temperature) Pressure units to use (select at least one): atmospheres (atm), kilopascals (kPa) Temperature units to use (select at least one): degrees Celsius (°C), kelvins (K) Volume units to use (select at least one): liters (L), milliliters (mL) Ideal gas law units to use (select at least one for ideal gas problems): moles Units before & after (does not apply to ideal gas problems): Before and after units are consistent within a problem (easier) Display problems as: List of givens and wanted (easier) Display gases as: Chemical formulas
Gas Laws	Type of problems (select at least one: Combined Gas Law (pressure, volume & temperature) Pressure units to use (select at least one): atmospheres (atm), kilopascals (kPa) Temperature units to use (select at least one): degrees Celsius (°C), kelvins (K) Volume units to use (select at least one): liters (L), milliliters (mL) Ideal gas law units to use (select at least one for ideal gas problems): moles Units before & after (does not apply to ideal gas problems): Before and after units are consistent within a problem (easier) Display problems as: Word problems (more challenging) Display gases as: Mix & match (both formulas and names)
Gas Laws	Type of problems (select at least one: Ideal Gas Law Pressure units to use (select at least one): kilopascals (kPa) Temperature units to use (select at least one): degrees Celsius (°C), kelvins (K) Volume units to use (select at least one): liters (L) Ideal gas law units to use (select at least one for ideal gas problems): moles Units before & after (does not apply to ideal gas problems): Before and after units are consistent within a problem (easier) Display problems as: List of givens and wanted (easier) Display gases as: Chemical formulas
Gas Laws	Type of problems (select at least one: Ideal Gas Law Pressure units to use (select at least one): atmospheres (atm), kilopascals (kPa) Temperature units to use (select at least one): degrees Celsius (°C), kelvins (K) Volume units to use (select at least one): liters (L), milliliters (mL) Ideal gas law units to use (select at least one for ideal gas problems): grams, moles Units before & after (does not apply to ideal gas problems): Before and after units are consistent within a problem (easier) Display problems as: List of givens and wanted (easier) Display gases as: Chemical formulas
Gas Laws	Type of problems (select at least one: Ideal Gas Law Pressure units to use (select at least one): atmospheres (atm), kilopascals (kPa) Temperature units to use (select at least one): degrees Celsius (°C), kelvins (K) Volume units to use (select at least one): liters (L), milliliters (mL) Ideal gas law units to use (select at least one for ideal gas problems): grams, moles, particles Units before & after (does not apply to ideal gas problems): Before and after units are consistent within a problem (easier) Display problems as: Word problems (more challenging) Display gases as: Mix & match (both formulas and names)
Calorimetry	Heat units to use: joules (J) Temperature units to use: kelvins (K) Quantity units to use: grams Display problems as: List of given and wanted values (easier)
Calorimetry	Heat units to use: calories (cal), joules (J) Temperature units to use: degrees Celsius (°C), kelvins (K) Quantity units to use: grams, moles Display problems as: List of given and wanted values (easier)
Calorimetry	Heat units to use: calories (cal), joules (J) Temperature units to use: degrees Celsius (°C), kelvins (K) Quantity units to use: grams, moles Display problems as: Word problems (more challenging)
Enthalpy Calculations	Heat units to use: kilojoules (kJ) Chemical quantity units to use: moles Display substances as: both names and formulas and together Display problems as:
Enthalpy Calculations	Heat units to use: kilojoules (kJ) Chemical quantity units to use: grams Display substances as: both names and formulas and together Display problems as:
Enthalpy Calculations	Heat units to use: kilojoules (kJ), kilocalories (kcal) Chemical quantity units to use: grams, moles Display substances as: both names and formulas and together Display problems as: Word problems (more challenging)
Enthalpy Calculations	Heat units to use: kilojoules (kJ), kilocalories (kcal) Chemical quantity units to use: grams, moles Display substances as: names only Display problems as: Word problems (more challenging)
Thermochemical Equations	Chemical equations are: Balanced Type of problems: Calculate heat absorbed or released when given amount of substance Heat values: Heat values can be entered as absolute values Type of problems: Simple stoichiometry only (one given, one wanted) Percent yield: Units to use (select at least one): moles Chemical formulas or names: Chemical formulas
Thermochemical Equations	Chemical equations are: Balanced Type of problems: Calculate heat absorbed or released when given amount of substance Heat values: Heat values can be entered as absolute values Type of problems: Simple stoichiometry only (one given, one wanted) Percent yield: Units to use (select at least one): grams Chemical formulas or names: Chemical formulas
Thermochemical Equations	Chemical equations are: Balanced Type of problems: Calculate amount of substance required when given heat (not with limiting reagents) Heat values: Heat values can be entered as absolute values Type of problems: Simple stoichiometry only (one given, one wanted) Percent yield: Units to use (select at least one): grams Chemical formulas or names: Chemical formulas
Thermochemical Equations	Chemical equations are: Unbalanced Type of problems: A mix of both types of problems Heat values: Heat values can be entered as absolute values Type of problems: Simple stoichiometry only (one given, one wanted) Percent yield: Units to use (select at least one): grams, moles Chemical formulas or names: Mix & match (both formulas and names)
Thermochemical Equations	Chemical equations are: Balanced Type of problems: Calculate heat absorbed or released when given amount of substance Heat values: Heat values can be entered as absolute values Type of problems: Limiting reagents only (two given reactants, heat wanted) Percent yield: Units to use (select at least one): grams Chemical formulas or names: Chemical formulas
Thermochemical Equations	Chemical equations are: Balanced Type of problems: A mix of both types of problems Heat values: Heat values can be entered as absolute values Type of problems: Simple stoichiometry only (one given, one wanted) Percent yield: Include percent yield calculations in problems (very challenging!) Units to use (select at least one): grams Chemical formulas or names: Chemical formulas
Concentrations of Solutions	Type of problems (select at least one): Molarity (i.e., M = n/V) Volume units to use (select at least one): Liters (L) Solute units to use (select at least one for molarity problems): moles Display problems as: List of givens and wanted (easier) Display substances as: Chemical formulas
Concentrations of Solutions	Type of problems (select at least one): Molarity (i.e., M = n/V) Volume units to use (select at least one): Liters (L), milliliters (mL) Solute units to use (select at least one for molarity problems): grams, moles Display problems as: List of givens and wanted (easier) Display substances as: Chemical formulas
Concentrations of Solutions	Type of problems (select at least one): Molarity (i.e., M = n/V) Volume units to use (select at least one): Liters (L), milliliters (mL) Solute units to use (select at least one for molarity problems): grams, moles Display problems as: Display substances as: Chemical names
Concentrations of Solutions	Type of problems (select at least one): Dilution (i.e., M₁V₁ = M₂V₂) Volume units to use (select at least one): Liters (L), milliliters (mL) Solute units to use (select at least one for molarity problems): moles Display problems as: List of givens and wanted (easier) Display substances as: Chemical formulas
Solubility	Type of questions: Calculate solubility from K_sp Solubility concentrations in: Molarity (mol/L) Display chemical formulas or names: Both names and formulas together Display problems as: List of givens and wanted (easier)
Solubility	Type of questions: Calculate solubility product constant (K_sp) Solubility concentrations in: Molarity (mol/L) Display chemical formulas or names: Both names and formulas together Display problems as: List of givens and wanted (easier)
Solubility	Type of questions: Determine concentration of an ion in a saturated solution Solubility concentrations in: Molarity (mol/L) Display chemical formulas or names: Both names and formulas together Display problems as: List of givens and wanted (easier)
Solubility	Type of questions: Calculate solubility from K_sp, Calculate solubility product constant (K_sp), Determine concentration of an ion in a saturated solution Solubility concentrations in: Grams per 100 mL Display chemical formulas or names: Both names and formulas together Display problems as: List of givens and wanted (easier)
Solubility	Type of questions: Calculate solubility from K_sp, Calculate solubility product constant (K_sp), Determine concentration of an ion in a saturated solution Solubility concentrations in: Molarity (mol/L), Grams per 100 mL Display chemical formulas or names: Both names and formulas together Display problems as: Word problems (more challenging)
Chemical Equilibrium	Type(s) of questions: Write equilibrium constant expressions (Q, K_c and K_p) Chemical equations are: Balanced Display problems as: List of givens and wanted (easier) Given values are: Random (more realistic) Units to use (select at least one): M
Chemical Equilibrium	Type(s) of questions: Convert between K_c and K_p Chemical equations are: Balanced Display problems as: List of givens and wanted (easier) Given values are: Random (more realistic) Units to use (select at least one): atmospheres, grams, M, moles
Chemical Equilibrium	Type(s) of questions: Calculate reaction quotient (Q) or equilibrium constant (K_c or K_p), Calculate chemical quantities in equilibrium reactions Chemical equations are: Balanced Display problems as: List of givens and wanted (easier) Given values are: Random (more realistic) Units to use (select at least one): atmospheres, grams, M, moles
Chemical Equilibrium	Type(s) of questions: Write equilibrium constant expressions (Q, K_c and K_p), Convert between K_c and K_p, Calculate reaction quotient (Q) or equilibrium constant (K_c or K_p), Calculate chemical quantities in equilibrium reactions Chemical equations are: Unbalanced Display problems as: Word problems (more challenging) Given values are: Random (more realistic) Units to use (select at least one): atmospheres, grams, M, moles
pH & pOH Calculations	Type of questions: Calculate pH from hydrogen ion concentration [H⁺], Calculate hydrogen ion concentration [H⁺] from pH Display problems as: List of givens and wanted (easier)
pH & pOH Calculations	Type of questions: Calculate pOH from hydrogen ion [H⁺] or hydroxide ion concentration [OH^-], Calculate hydroxide ion concentration [OH^-] from pH or pOH Display problems as: List of givens and wanted (easier)
pH & pOH Calculations	Type of questions: Calculate pH from hydrogen ion concentration [H⁺], Calculate hydrogen ion concentration [H⁺] from pH, Calculate pOH from hydrogen ion [H⁺] or hydroxide ion concentration [OH^-], Calculate hydroxide ion concentration [OH^-] from pH or pOH Display problems as: Word problems (more challenging)
Acid-Base Equilibrium	Type of questions: Calculate weak acid concentration, K_a or pH, Calculate weak base concentration, K_b or pH Display problems as: List of givens and wanted (easier)
Acid-Base Equilibrium	Type of questions: Calculate percent ionization, ion or solution concentration, or pH Display problems as: List of givens and wanted (easier)
Acid-Base Equilibrium	Type of questions: Calculate weak acid concentration, K_a or pH, Calculate weak base concentration, K_b or pH, Calculate percent ionization, ion or solution concentration, or pH Display problems as: Word problems (more challenging)
Acid-Base Neutralization	Type of questions: Strong acid-strong base neutralization Display problems as: List of givens and wanted (easier)
Acid-Base Neutralization	Type of questions: Weak acid-strong base neutralization, Strong acid-weak base neutralization Display problems as: List of givens and wanted (easier)
Acid-Base Neutralization	Type of questions: Strong acid-strong base neutralization, Weak acid-strong base neutralization, Strong acid-weak base neutralization Display problems as: Word problems (more challenging)
Elements & Isotopes	Question types: Solve for isotope notation
Elements & Isotopes	Question types: Solve for isotope name
Elements & Isotopes	Question types: Solve for isotope notation, Solve for isotope name, Solve for number of subatomic particles
Nuclear Reactions	Nuclear reaction types: Alpha decay, Beta (minus) decay, Neutron decay, Positron (beta plus) decay Display problems as: Equations with isotope symbols (easier)
Nuclear Reactions	Nuclear reaction types: Electron capture, Fission, Neutron activation Display problems as: Equations with isotope symbols (easier)
Nuclear Reactions	Nuclear reaction types: Alpha decay, Beta (minus) decay, Electron capture, Fission, Neutron activation, Neutron decay, Positron (beta plus) decay Display problems as: Equations with isotope symbols (easier)
Nuclear Reactions	Nuclear reaction types: Alpha decay, Beta (minus) decay, Electron capture, Fission, Neutron activation, Neutron decay, Positron (beta plus) decay Display problems as: Word problems (more challenging)