GENERAL CHEMISTRY 1: Chemical Foundations Flashcards
The sample corresponds to Chapter 1: Chemical Foundations for General Chemistry I.
What is Chemistry?
Chemistry is the study of the composition of matter, its
properties, and the changes it undergoes. Chemistry aims to connect the macroscopic behavior of matter we observe to the microscopic behavior of atoms and molecules.
What is a hypothesis?
A hypothesis is a tentative explanation for an observation.
What is a theory?
A theory (also referred to as a model) is a set of tested hypotheses that gives an overall explanation of some natural phenomenon. A theory attempts to explain why something happens.
What is a law?
A law is a summary of measurable behavior and summarizes what happens. A law will usually be supported by a mathematical expression.
A ______________ is best described as an educated guess.
A hypothesis is best described as an educated guess.
What is the fundamental difference between a theory and a law?
A law will summarize a series of related observations, while a theory will explain the underlying reasons for them.
A law is the “what” whereas a theory is “why.”
True or False:
Both a theory and a hypothesis can be supported or not supported by experiments.
True
What is a qualitative observation?
Qualitative observations are descriptive and do not involve a number.
What is a quantitative observation?
Quantitative observations answer the question “how much?” and involve both a unit and a number.
Which of the following statements could be described as an observation?
Cats are the best animal.
Cats cannot bark.
People who do not like cats are the worst.
Cats are the best animal. = Opinon, not an observation.
Cats cannot bark. = Observation
People who do not like cats are the worst. = Opinon, not an observation.
True or False:
“My Chemistry class has more students than your Chemistry class” is an example of a quantitative observation.
False: This would be a qualitative statement.
Remember that quantitative observations must contain a number and a unit
What are the SI units for mass, length, and time, respectively?
The SI unit for mass is the kilogram (kg).
The SI unit for length is meter (m).
The SI unit for time is second (s).
What are the SI units for electric current, amount of substance, and luminous intensity, respectively?
The SI unit for electric current is ampere (A).
The SI unit for amount of substance is the mole (mol).
The SI unit for luminous intensity is the candela (cd).
True or False:
The SI unit for temperature is kelvin (K)
True
Convert 6755 into standard scientific notation.
Convert 0.00000756 into standard scientific notation.
Provide the correct abbreviations for each of the following units of measurement: milliliter, nanosecond, picometer, and microgram.
millilter = mL
nanosecond = ns
picometer = pm
microgram = μg
1 dm = ??? m
1 m = ??? dm
dm = decimeter
1 cm = ??? m
1 m = ??? cm
cm = centimeter
1 mg = ??? g
1 g = ??? mg
mg = milligram
1 μm = ??? m
1 m = ??? μm
μm = micrometer
1 ns = ??? s
1 s = ??? ns
ns = nanosecond
1 pg = ??? g
1 g = ??? pg
pg = picogram
1 fs = ??? s
1 s = ??? fs
fs = femtosecond
1 hm = ??? m
1 m = ??? hm
hm = hectometer
1 kg = ??? g
1 g = ??? kg
kg = kilogram
1 Mg = ??? g
1 g = ??? Mg
Mg = Megagram
1 Gg = ??? g
1 g = ??? Gg
Gg = gigagram
What is the difference between mass and weight?
Mass describes the quantity of matter contained within a object.
Weight has to do with the force of gravity acting on an object and is proportional to the mass of an object.
True or False:
Your body mass is the same on the earth as it is on the moon.
True
Your mass is the same, but your weight would be different.
The degree of agreement among several measurements of the same quantity is called what?
Precision
The agreement of a particular value with the true value is called what?
Accuracy
True or False:
It is possible for a series of measurements to be precise, but not accurate.
True
Think about a series of darts clumped together but not on the bullseye.
Describe the image below in terms of accuracy and precision.
High precision, poor accuracy
Darts are clumped together (precise), but not near the bullseye.
How many significant figures are in the numbers shown below?
550 seconds
550.0 seconds
550.00 seconds
550 seconds = 2 sig figs
550.0 seconds = 4 sig figs
550.00 seconds = 5 sig figs
How many significant figures are in the numbers shown below?
4.0001 meters
0.00706 meters
0.050410 meters
4.0001 meters = 5 sig figs
0.00706 meters = 3 sig figs
0.050410 meters = 5 sig figs
What are two situations where numbers will have unlimited (infinite) significant figures?
- Counting numbers are exact values and cannot be made more accurate. Example: “I have 5 pencils.”
- Known conversions are exact values and cannot be made more accurate.
Example: “1 foot = 12 inches”
True or False:
In the statment “There are 95 people in my Chemistry class”, the 95 would have 2 significant figures.
False: This would have unlimited (infinite) significant figures.
Remember counting numbers will have unlimited significant figures.
True or False:
Measurements are generally made by recording all certain digits plus one uncertain digit.
True
This is the concept behind significant figures.
What is the diffference in determining the number of significant figures when multiplying/dividing versus adding/subtracting?
When multiplying/dividing two or more numbers, your answer must contain the same number of sig figs as the value with the fewest number of sig figs.
When adding/subtracting two or more numbers, your answer must contain the same number of decimal places as the value in the equation with the fewest decimal places.
Find the permimeter and area of the rectangle show below.
Hint: Report answers to the correct number of significant figures.
Remember the different rules for sig figs when multiplying/dividing versus adding/subtracting
True or False:
The boiling point of water on the Fahrenheit scale is 212 degrees.
True
True or False:
Negative values are possible in the Celsius, Fahrenheit, and Kelvin scales.
False: They are possible in the Celsius and Fahrenheit scales, but not the Kelvin scale.
All temperatures on the Kelvin scale are positive values.
True or False:
The freezing point of water on the Celsius scale is 0 degrees.
True
Describe the solid state of matter.
Solids are rigid, incompressible, and have a fixed volume and shape.
Describe the liquid state of matter.
Liquids will flow, are incompressible, have a fixed volume but not a fixed shape (they will take the shape of the container they are in).
Describe the gas state of matter.
Gases will flow, are compressible, and have no fixed volume of shape.
True or False:
Both liquids and gases have the ability to flow.
True
True or False:
Both liquids and gases are compressible.
False: Only gases are compressible.
What state of matter is shown in the diagram below?
Gas
The particles are taking the volume and shape of the container.
Which state of matter has a definite volume but not a definite shape?
Liquids
What is a pure substance?
A pure substance involves matter made up of all the same type of particle.
What is an element?
A pure substance made up of only one kind of atom. Can be a monoatomic elemental substance (such as Na (s)) or a molecular elemental substance (such as O2 (g)).
What is a molecule?
Molecules are two or more atoms chemically joined together.
What is a compound?
Compounds are pure substances made up of more than one kind of atom.
True or False:
All molecules can be described as compounds, but not all compounds can be described as molecules.
False: All compounds can be described as molecules, but not all molecules can be described as compounds.
Remember compounds have to have at least two different atoms, whereas in molecules the atoms can be the same or different.
What is a mixture?
A mixture is matter made up of different types of particles.
What is the difference between a homogeneous mixture versus a heterogeneous mixture?
In homogeneous mixtures, the different particles are evenly distributed (uniform).
In heterogeneous mixtures, the different particles are not evenly distributed. In these mixtures, particles tend to congregate with one another.
Describe the following as heterogenous or homogeneous mixtures:
Air
Black coffee
Milk
Air and coffee are homogenous mixtures.
Milk is a heterogenous mixture.
A solution can also be referred to as what?
A solution can also be referred to as a homogeneous mixture.
True or False:
A sample of iron could be described as a homogenous mixture.
False: Iron could be described as an element (it is not a mixture at all).
Is the diagram a pure substance or a mixture?
Diagram is a pure substance, more specifically a compound.
What is a physical change?
In a physical change, the macroscopic properties of the substance changes, however, the individuals particles of the substance do not change.
What is a chemical change?
In a chemical change, the particles of the substance change and new substances are created.
What is a physical property? Provide at least five different examples.
Physical Properties are properties that can be observed and measured without changing the composition of the substance.
Examples of physical properties include color, state of matter, melting point, boiling point, density, solubility, conductivity, malleability, ductility, and viscosity.
Describe each statement as a chemical or physical change.
Water on the stove boils.
Sugar dissolves in coffee.
A steak is grilled.
A car rusts.
Water on the stove boils. = Physical change.
Sugar dissolves in coffee. = Physical change.
A steak is grilled. = Chemical change.
A car rusts. = Chemical change.
List three different methods used for separating mixtures and describe each.
Filtration is used to separate a solid from a liquid.
Distillation is used to separate liquids based on a difference in their boiling points.
Chromatography is used to separate substances in a solution by differences in affinity for a surface.
Which separation technique is based on differences in the volatility of the substances to be separated?
Distillation
What is an intensive property?
An intensive property is a bulk property, meaning that it is a physical property of a system that does not depend on the size or the amount of sample in the system.
What is an extensive property?
An extensive property is a physical property of a system that changes with the size of the sample measured (it is additive).
Describe each of the following as an intensice or extensive property:
Density
Mass
Volume
Boiling point
Conductivity
Density = Intensive property
Mass = Extensive property
Volume = Extensive property
Boiling point = Intensive property
Conductivity = Intensive property
What is the relationship between density, mass, and volume?
Density = mass (g) / volume (ml or cm^3)
There is a direct relationship betweem mass and density. As mass increase, so will the density. As mass decreases, so will the density.
There is an indirect relationship between volume and denisty. As volume increases, density will decrease. As volume decreases, density will increase.
Liquid A (density = 0.750 g/mL), liquid B (density = 0.958 g/mL), and liquid C (density = 1.256 g/mL) are placed in a beaker and allowed to separate.
Place these liquids in order from bottom of the beaker to the top of the beaker.
More dense objects will sink, less dense will float.
From bottom to top: Liquid C, liquid B, liquid A.
