Chapter One: Chemistry And Measurements
Chapter One: Chemistry and Measurements
Describe the “scientific method” in terms of hypothesis, experiment, theory, and law. • The scientific method begins with observation (a woodpecker is make a hole in a tree). • Followed by hypothesis (because the tree has termites) • Followed by experiment (a collection of woodpeckers is observed in a setting in which trees have no termites). • Leading to a refined hypothesis and further experiment to a possible theory (woodpeckers only make holes when making a nest) • Leading to a “law” (if many additional observations cannot refute the theory).
State the Law of Conservation of Mass and use it to determine unknown masses of reactant or product in a chemical reaction. • In chemical reactions, atoms are …show more content…
neither created nor destroyed so that the mass of the reactants must equals the mass of the products. [pic] [pic] [pic] How many grams of KCL must be formed? [pic]
Distinguish between, define, and give an example of physical change and chemical change. • In a physical change, no new substances are formed; no internal chemical bonds break and reform; only the physical state changes. [pic] o The water molecule [pic] is structurally the same o [pic] are endothermic physical changes • In a chemical change, new compounds or elements forms due to breaking and forming chemical bonds. [pic] o Exothermic chemical change
Distinguish between a physical property and a chemical property and give examples for each. • Physical properties include density, melting point, and other measurements related to the physical state. o Na is a soft solid at solid at room temperature • Chemical properties relate to chemical reactivity, gaining or losing electrons, acidity, etc. o Na reacts with H2O at room temperature o F2 is a better oxidizing agent than O2 o Cl has a higher electron affinity than F o HCl is a stronger acid than HF
Distinguish between element, compound, and mixture. • Pure substances are those with physical and chemical properties that cannot change. o Elements- cannot be broken down into other pure substances o Compounds- can be broken down to elements [pic] • Mixtures contain two or more pure substances, which can be separated by physical methods (filtering, distillation, etc.) o Homogeneous- same properties throughout the sample (air) o Heterogeneous- variable composition
Distinguish between a homogeneous and heterogeneous mixture. • Homogeneous- the same throughout o 0.100 M NaCl o a balloon containing CO2 and O2 • Heterogeneous- variable misture o 1lb or brown rice and 1lb of white rice casually mixed together o the members of the class are a heterogeneous mixture
Define accuracy and precision. • Accuracy is the agreement of a measurement with the actual or true value o A student analyzes a “primary standard” containing 5.000% Cu and obtain 3 experimental values of 4.866%, 4.922%, and 5.001%. 5.001% is the most accurate value. • Precision is the degree of spread among replicated values. Note that precision does not simply imply/guarantee accuracy o Another student using faulty equipment reports values of 4.777%, 4.776%, and 4.777%. This is excellent precision, but poor accuracy
Convert a quantity and its units to different units using conversion factors which are provided. • Do not need to memorize conversion or metric prefixes. Convert [pic] to [pic] [pic] Convert 1.00picometers to millimeters [pic]
State the basic units of length, mass, time, amount, of substance, and time in the “SI” system. • Length = Meter • Mass = Kilograms • Time = Second • Temperature = Kelvin • Amount = Mole • Electric Current = Ampere • Luminous Intensity = Candela • Energy Units = Joule
Convert between and among Fahrenheit, Celsius, and Kelvin temperature.
[pic] [pic] [pic]
Is there a temperature at which F and C are identical?
[pic]
Define density and solve numeric problems using this definition and appropriate values of density, mass, length, and volume. • Density is a physical property, which is [pic]. • For solids and liquids the units are [pic] or [pic] [pic]. • For gases the units are [pic]. Note that density of a gas varies significantly with temperature. How many grams would gold occupy in a 2.00L block of gold? The density of gold is 19.7g/cm3. [pic]
Solve conversion problems such as “convert 2.0 lbs/ft3 to grams/cm3” using the method of dimensional analyses. • In dimensional analysis, units must cancel, excepts for units of the answer and the conversion factors must be correct. [pic] *squaring/cubing identities is sometimes necessary*
Determine the number of significant figures in measured values and in any numeric calculation based on these
values.
• Significant figures reflect the measuring ability of the instrument used in an experiment o 50mL graduated cylinder: 46.1mL (3 significant figures) • The number of significant figures in a conversion factor is essentially infinite • Multiplication/Division = the least number of significant figures • Adding/Subtraction = the least number of decimal places
Describe the “scientific method” in terms of hypothesis, experiment, theory, and law. • The scientific method begins with observation (a woodpecker is make a hole in a tree). • Followed by hypothesis (because the tree has termites) • Followed by experiment (a collection of woodpeckers is observed in a setting in which trees have no termites). • Leading to a refined hypothesis and further experiment to a possible theory (woodpeckers only make holes when making a nest) • Leading to a “law” (if many additional observations cannot refute the theory).
State the Law of Conservation of Mass and use it to determine unknown masses of reactant or product in a chemical reaction. • In chemical reactions, atoms are …show more content…
neither created nor destroyed so that the mass of the reactants must equals the mass of the products. [pic] [pic] [pic] How many grams of KCL must be formed? [pic]
Distinguish between, define, and give an example of physical change and chemical change. • In a physical change, no new substances are formed; no internal chemical bonds break and reform; only the physical state changes. [pic] o The water molecule [pic] is structurally the same o [pic] are endothermic physical changes • In a chemical change, new compounds or elements forms due to breaking and forming chemical bonds. [pic] o Exothermic chemical change
Distinguish between a physical property and a chemical property and give examples for each. • Physical properties include density, melting point, and other measurements related to the physical state. o Na is a soft solid at solid at room temperature • Chemical properties relate to chemical reactivity, gaining or losing electrons, acidity, etc. o Na reacts with H2O at room temperature o F2 is a better oxidizing agent than O2 o Cl has a higher electron affinity than F o HCl is a stronger acid than HF
Distinguish between element, compound, and mixture. • Pure substances are those with physical and chemical properties that cannot change. o Elements- cannot be broken down into other pure substances o Compounds- can be broken down to elements [pic] • Mixtures contain two or more pure substances, which can be separated by physical methods (filtering, distillation, etc.) o Homogeneous- same properties throughout the sample (air) o Heterogeneous- variable composition
Distinguish between a homogeneous and heterogeneous mixture. • Homogeneous- the same throughout o 0.100 M NaCl o a balloon containing CO2 and O2 • Heterogeneous- variable misture o 1lb or brown rice and 1lb of white rice casually mixed together o the members of the class are a heterogeneous mixture
Define accuracy and precision. • Accuracy is the agreement of a measurement with the actual or true value o A student analyzes a “primary standard” containing 5.000% Cu and obtain 3 experimental values of 4.866%, 4.922%, and 5.001%. 5.001% is the most accurate value. • Precision is the degree of spread among replicated values. Note that precision does not simply imply/guarantee accuracy o Another student using faulty equipment reports values of 4.777%, 4.776%, and 4.777%. This is excellent precision, but poor accuracy
Convert a quantity and its units to different units using conversion factors which are provided. • Do not need to memorize conversion or metric prefixes. Convert [pic] to [pic] [pic] Convert 1.00picometers to millimeters [pic]
State the basic units of length, mass, time, amount, of substance, and time in the “SI” system. • Length = Meter • Mass = Kilograms • Time = Second • Temperature = Kelvin • Amount = Mole • Electric Current = Ampere • Luminous Intensity = Candela • Energy Units = Joule
Convert between and among Fahrenheit, Celsius, and Kelvin temperature.
[pic] [pic] [pic]
Is there a temperature at which F and C are identical?
[pic]
Define density and solve numeric problems using this definition and appropriate values of density, mass, length, and volume. • Density is a physical property, which is [pic]. • For solids and liquids the units are [pic] or [pic] [pic]. • For gases the units are [pic]. Note that density of a gas varies significantly with temperature. How many grams would gold occupy in a 2.00L block of gold? The density of gold is 19.7g/cm3. [pic]
Solve conversion problems such as “convert 2.0 lbs/ft3 to grams/cm3” using the method of dimensional analyses. • In dimensional analysis, units must cancel, excepts for units of the answer and the conversion factors must be correct. [pic] *squaring/cubing identities is sometimes necessary*
Determine the number of significant figures in measured values and in any numeric calculation based on these
values.
• Significant figures reflect the measuring ability of the instrument used in an experiment o 50mL graduated cylinder: 46.1mL (3 significant figures) • The number of significant figures in a conversion factor is essentially infinite • Multiplication/Division = the least number of significant figures • Adding/Subtraction = the least number of decimal places