CHAPTER ONE: CHEMISTRY AND MEASUREMENTS Flashcards
In general, what is Chemistry?
F
The study of matter (all the substances that make up our world)
More specifically, what is Chemistry the study of?
M
Chemistry is the study of the structure, physical properties and transformation (chemical properties/reactions) of matter.
Define MATTER
F
Matter is anything with mass (weight) and volume (takes up space). Has atoms.
Explain MASS vs. WEIGHT
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Mass- the amount of matter contained in an object. Does NOT depend on location.
Weight- the amount of force exerted by gravity on an object. DOES depend on location
Give the equation for FORCE
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Force=mass x acceleration (F= m x a)
EX: Newton (N) = (kg)(m/s^2)
Along with changes, there is ________ being transformed. It can be ________, ________, ___________, _______________.
F
Energy.
Heat, light, sound, electricity
What are the 3 main kinds of substances from a chemistry point of view?
F
- Elements
- Compounds (chemically bonded atoms of different elements)
- Mixtures (any number of different elements of compounds physically mixed together- not bonded). Air is a mixture of nitrogen and oxygen.
How do you differentiate between PURE SUBSTANCE and a MIXTURE?
F
Can it be separated without changing the substances present?
YES- mixture (more than one substance “mixed”)
NO- pure substance
How do you differentiate between HETEROGENOUS and HOMOGENEOUS MIXTURES?
F
Can you see the different substances?
YES- heterogeneous
NO- homogeneous
How do you differentiate between a COMPOUND and an ELEMENT, in terms of pure substances?
F
Can it be separated at all?
YES- compound
NO- element (example: GOLD- cannot make it a simpler substance; only made of itself)
Differentiate between these 2 types of matter: PURE SUBSTANCE/CHEMICAL and MIXTURES OF SUBSTANCES
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Pure substance/chemical= anything that can be described by a chemical formula. Ex: AR (argon gas), H20
Mixtures of substances= cannot be described by a single chemical formula
What is the SCIENTIFIC METHOD? (definition and 4 specific steps)
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Definition: General principles or guidelines for how a scientist thinks.
- OBSERVATIONS: data, natural phenomena, natural laws
- HYPOTHESES: tentative proposal (testable)
- EXPERIMENT: test (control of all variables except those of interest)
- THEORY/MODEL (CONCLUSION): explanation which allows for prediction
How many ELEMENTS exist?
F
118
Are ELEMENTS naturally occurring or man-made?
F
Both.
FOUND IN NATURE: Elements from 1-92 can be found in nature, with the exception of 43 and 61.
MAN-MADE: The first manmade elements were made in 1939 at UC Berkeley. Elements 93 and on are all man-made.
The PERIODIC TABLE is organized by ______________________
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Similarity in element properties
Elements on the Periodic Table have a ______ and a __________. List 5 rules about how they should be written.
F
Elements on the Periodic Table have a NAME (language dependent) and a SYMBOL (universal).
5 rules about how they should be written:
- spelling counts
- do NOT capitalize
- the symbol will be 1 or 2 letters (3-letter symbols represent unnamed elements)
- 1st letter of symbol capitalized
- 2nd letter of symbol must be lower case
What are the three states of matter (and the color) at room temperature?
F
SOLID- black
LIQUID- blue
GAS- red
How is the Periodic Table organized?
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It is organized into GROUPS vertically- the columns-there are 18 groups (#1-#18); grouped by similar properties.
It is organized into PERIODS horizontally- the rows (#1-#7), grouped by having the same number of atomic orbitals.
What is SCIENTIFIC NOTATION? How are numbers written in Scientific Notation?
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Scientific notation is a way of writing numbers that are too big or too small to be conveniently written in decimal form. Scientific notation has a number of useful properties and is commonly used in calculators and by scientists, mathematicians and engineers.
In scientific notation, there are three parts: a coefficient, a power of 10 and a measurement unit.
All numbers are written in the form a x 10^b
Examples:
- 0.00865= 8.65 x 10^-3
- 57827= 5.7827 x 10^4
What is a CHEMICAL?
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a substance that always has the same composition and properties wherever it is found
What are the 3 common scales of TEMPERATURE and their relative numbers for the lower limit (absolute zero), freezing and boiling?
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Kelvin (K) 0K……………273 K………….373K
Celsius (C) -273C………………..0C…………..100C
Fahrenheit (F) -460F……………….32F………….212F
What is the International System of Units (SI, or Systeme International)?
M
The SI is a modification of the metric system that was adopted in 1960 by scientists throughout the world. It is now the official system of measurement throughout the world except for the USA.
MEASUREMENTS:
* how is LENGTH described in Metric, SI, and the US system?
M
Metric- meter (m)
SI- meter (m)
US- feet (ft)
MEASUREMENTS:
* how is VOLUME described in Metric, SI, and the US system?
M
Metric- liter (L)
SI- cubic meters (m^3)
US- gallon (gal)
MEASUREMENTS:
* how is MASS described in Metric, SI, and the US system?
M
Metric- gram (G)
SI- kilogram (kg)
US- pound (lb)
MEASUREMENTS:
* how is TEMPERATURE described in Metric, SI, and the US system?
M
Metric- degree Celsius (^oC)
SI- kelvin (K)
US- degree Fahrenheit (^oF)
MEASUREMENTS:
* how is TIME described in Metric, SI, and the US system?
M
Metric- second (s)
SI- second (s)
US- second (s)
What are MEASURED NUMBERS?
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Measured numbers are the numbers you obtain when you measure a quantity such as your height, weight or temperature.
In Measured Numbers, what are the SIGNIFICANT FIGURES (SF’s)?
M
SF’s are all the digits, including the estimated digit. Nonzero numbers are always counted as SF’s. However, a zero may or may not be a significant figure, depending on its position in a number. (see next 2 cards)
A number is a SIGNIFICANT figure if it is _______, ________, ________, _______
M
- not a zero
- a zero between nonzero digits
- a zero at the end of a decimal number
- in the coefficient of a number written in scientific notation
(see page 14 in the text for examples)
A zero is NOT SIGNIFICANT it is is ______, ________.
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- at the beginning of a decimal number
- used as a placeholder in a large number without a decimal point
(see page 14 in the text for examples)
Describe the concept of UNCERTAINTY in measurements.
Lab instruments sometimes specific ______
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All measurements contain UNCERTAINTY, which is expressed by the number of SF’s written in the measured vale. The last digit always carries the uncertainty.
Lab instruments sometimes specific the amount of uncertainty EX: 1.85g (+or- 0.03g) range is 1.82-1.88g
What are EXACT NUMBERS?
M
Exact numbers are NOT measured with a measuring tool and are obtained by:
- counting items (EX: how many classes do you have?) OR
- using a definition that compares two units of the same measuring system (EX: state the number of seconds in one minute)
SF’s in CALCULATIONS. What are the rules for:
* Rounding Off
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Rounding off- when measuring, if you end up with more numbers than required in the answer, here is how you round off so that you have the correct # of SF’s:
- If the first digit to be dropped is 4 or less, then it and all following digits are simply dropped from the number.
- If the first digit to be dropped is 5 or greater, then the last retained digit of the number is increased by 1.
SF’s in CALCULATIONS. What is the rule for:
* Multiplication and division
M
In multiplication and division, the final answer is written so it has the same number of SF’s as the measurement with the fewest SF’s.
EX: 0.400995 mg/mL is limited by first number for SF’s so will be written as 0.401 mg/mL
SF’s in CALCULATIONS. What is the rule for:
* Addition and subtraction
M
In addition and subtraction, the final answer is written so it has the same number of decimal places as the measurement with the fewest decimal places.
Ex: 10.21L + 0.0245L. Limited by first number so written as 10.23L
SF’s in CALCULATIONS. What is the rule for:
* Adding significant zeros
M
Sometimes a calculator display gives a small whole number. To report an answer with the correct number of SF’s, you may need to write significant zeroes after the calculator numbers.
EX: 4 should be written as 4.00 if the measurements each have 3 SF’s
What is the special feature of the SI and the metric systems?
M
A prefix can be placed in front of any until to increase or decrease its size by some factor of ten.
Ex: 1 kilometer (1 km) = 1000 meters (10^3 m)
Many problems in chemistry and the health sciences require a change of _________.
You can write any equality in the form of a fraction called a _________ _________. Describe this.
____ conversion factors are always possible from any equality and they are read as _______________.
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Units.
CONVERSION FACTOR: a fraction in which one of the quantities is the numerator and the other is the denominator. Be sure to include the units!
Ex: Two conversion factors for the equality of 1h=60 min…60 min/1 hour AND 1 hour/60 min
Two conversion factors are always possible. They are read as (using the above example) “60 minutes per one hour” and “1 hour per 60 minutes”.
How many inches are in a meter?
How many kilometers in a mile?
M
A meter is 39.4 inches (slightly longer than a yard, which is 36 inches)
1 km= 0.62 mi
How many centimeters are in an inch?
M
2.54 cm in one inch
How many of each of these are in a meter? * centimeters * inches * yard M
100 centimeters in a meter
- 4 inches in a meter
- 09 yards in a meter
What is the definition of VOLUME?
M
The amount of space a substance occupies
How many milliliters (mL) in a quart (qt)?
M
946 mL= 1 qt.
How many of these are in a liter (L?)
* milliliter (mL)
* quart (qt)
M
1000 mL in a L.
1.06 qt. in a L.
What is the definition of MASS?
M
The mass of an object is a measure of the quantity of material is contains.
How many of these are in a kilogram?
* grams (g)
* pounds (lb)
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1000 g in a kg
2.20 lb in a kg.
How many grams in 1 pound (lb)?
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454g = 1 lb
What is DENSITY?
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mass(g) / volume (mL) = g/mL
Describe VOLUME DISPLACEMENT
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The volume of a solid can be determined by volume displacement.
When a solid is completely submerged in water, it displaces a volume that is equal to the volume of the solid.
Prefix: tera * symbol * numerical value * scientific notation M
T
1 000 000 000 000
10^12
Prefix: giga * symbol * numerical value * scientific notation M
G
1 000 000 000
10^9
Prefix: mega * symbol * numerical value * scientific notation M
M
1 000 000
10^6
Prefix: kilo * symbol * numerical value * scientific notation M
k
1 000
10^3
Prefix: deci * symbol * numerical value * scientific notation M
d
0.1
10^-1
Prefix: centi * symbol * numerical value * scientific notation M
c
0.01
10^-2
Prefix: milli * symbol * numerical value * scientific notation M
m
0.001
10^-3
Prefix: micro * symbol * numerical value * scientific notation M
weird symbol- lower case u with a long front leg
0.000 001
10^ -6
Prefix: nano * symbol * numerical value * scientific notation M
n
0.000 000 001
10^-9
Prefix: pico * symbol * numerical value * scientific notation M
p
0.000 000 000 001
10^-12
What is an EQUALITY?
M
using numbers and units to relate the two units
Ex: 1h=60 min
When an equality shows the relationship for two units from the same system (metric or U.S.), it is considered a ________ and ______.
M
conversion factor
definition; exact (numbers in that definition are NOT used to determine significant figures).
When an equality shows the relationship of units from two different systems, the number is _____________
There is one exception to this- what is it?
M
MEASURED (counts toward the significant figures in a calculation). Ex: in the equality
1 lb = 454g, the measured number 454 has
3 sigfigs. The number one in 1 lb is considered as exact.
Exception- the relationship of 1 in = 2.54 cm: the value 2.54 has been defined as exact.
METRIC CONVERSION FACTORS
We can write metric conversion factors for ______ of the metric relationships.
M
ANY
Ex: the metric equality of 1 m= 100 cm
Two conversion factors (one is just the inverse of the other):
- 100 cm/1 m
- 1m/100cm
What is the usefulness of conversion factors enhanced by?
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By the fact that we can turn a conversation factor over and use its inverse.
METRIC-U.S. SYSTEM CONVERSION FACTORS:
When you have to convert from a unit is the U.S. system to a unit in the metric (or SI) system- give an example of how this would work using kg and lb
M
Ex: a relationship you could use is
1 kg = 2.20 lb
The corresponding conversion factors would be:
- 2.20 lb/1 kg
- 1 kg/2.20 lb
When an equality is specified within a problem that applies only to that problem, can we write conversion factors for relationships stated within that problem?
M
YES
Ex: the motorcycle was traveling at a speed of 85 km/h.
Equality: 1 h = 85 km
Conversion factors:
- 85 km/1 h AND
- 1 h/85 km
When a percent (%) is given in a problem, it means ___________________. To write a percent as a conversion factor, we choose a ___________ and express the numerical relationship of the parts of this ________ to _______ parts of the whole.
M
It means parts per 100 parts.
…choose a UNIT and express the numerical relationship of the parts of this UNIT to 100 parts of the whole.
Ex: a person has 18% body fat by mass. The percent quantity can be written as 18 mass units of body fat in every 100 mass units of body mass. Different mass unit (g, kg or lb can be used, but both units in the factor must be the same:
Percent quantity: 18% body fat by mass
Equality:
18 kg of body fat = 100 kg of body mass
Conversion factors:
- 100 kg body mass/18 kg body fat AND
- 18 kg body fat/100 kg body mass
When scientists want to indicate ratios with particularly small percentage values, they use numerical relationships called __________ or _________.
M
…numerical relationships called parts per million (ppm) or parts per billion (ppb)
The ratio of ppm is the same as ___________________________. (Give example and show equality and conversion factors)
The ratio of ppb equals the ___________________________.
M
The ratio of ppm is the same as the milligrams of a substance per kilogram (mg/kg). For example, the maximum amount of lead allowed by the FDA in glazed pottery bowls is 5 ppm, which is 5 mg/kg. Ex:
Percent quantity- 5 ppm of lead in glaze
Equality- 15 mg of lead= 1 kg of glaze
Conversion factors-
- 5 mg lead/1 kg glaze AND
- 1 kg glaze/5 mg lead
The ratio of ppb equals the micrograms per kilogram (weird symbol g/kg).
What is the relationship between a milliliter (mL) and a cubic centimeter (cm^3)?
M
They are the same
When you see 1 cm, you are reading about __________.
When you see 1 cc or 1cm^3 or 1 mL, you are reading about __________.
M
Length
Volume
The process of problem solving in chemistry often requires one or more _____ ______ to change a __________ unit to the ________ unit.
Explain the process.
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…one or more CONVERSION FACTORS to change a GIVEN unit to the NEEDED unit.
The process:
- for the problem, the unit of the GIVEN quantity and the unit of the NEEDED quantity are identified.
- from there, the problem is set up with one or more conversion factors used to convert the GIVEN unit to the NEEDED unit.
Example: GIVEN unit x one or more CONVERSION FACTORS= NEEDED unit
What does “per” mean?
M
divided by
Describe how to use two or more conversion factors in a problem to complete the change from a GIVEN unit to a NEEDED unit.
M
One factor can follow the other.
Each factor is arranged to cancel the preceding unit until the needed unit is obtained.
Once the problem is set up to cancel units properly, the calculations can be done without writing intermediate results.
What is DENSITY?
What can we predict from knowing the density of a substance?
M
The mass and volume of any object can be measured. If we compare the mass of the object to the its volume, we obtain a relationship called DENSITY.
Density=
mass of substance/volume of substance
Every substance has a unique density, which distinguishes it from other substances.
We can predict if a substance will sink or float in water (if less dense than water, it floats; if more dense than water, it sinks)
In the metric system, the densities of SOLIDS and LIQUIDS are usually expressed as _____ per __________ OR ______ per ______.
The densities of GASES are usually stated as ______ per ______.
M
… the density of SOLIDS and LIQUIDS are usually expressed as:
- grams per cubic centimeter (g/cm^2) OR
- grams per milliliter (g/mL)
… the density of GASES are usually expressed as:
* grams per liter (g/L)
Gases usually have lower densities than solids and liquids.
What are the FOUR steps for calculating DENSITY?
M
- State the given and needed quantities.
- Write the density expression.
- Express mass in grams and volume in milliliters (mL) or cm^3.
- Substitue mass and volume into the density expression and calculate the density.
What are the FOUR steps to using DENSITY as a conversion factor?
M
- State the GIVEN and NEEDED quantities.
- Write a plan to calculate the NEEDED quantity.
- Write equalities and their conversion factors including density.
- Set up problem to calculate the NEEDED quantity.
What is SPECIFIC GRAVITY (sp gr)?
Specific gravity is one of the few ________ values you will encounter in chemistry.
An instrument called a ___________ is often used to measure the specific gravity of fluids.
Specific Gravity is a relationship between the density of a substance and the density of water. It is calculated by dividing the density of a sample by the density of water (which is 1.00 g/mL at 4 degrees Celsius.
Specific Gravity=
density of sample/density of water
…one of the few UNITLESS values…
Hydrometer
List the common densities for:
- solids (s)
- liquids (l)
- gases (g)
SOLIDS (s): 0.25-20g/cm^3
LIQUIDS (l): 0.75-13.6g/mL
GASES (g): 0.1-2.0g/L
What is the equation for SPECIFIC GRAVITY?
SG= density of sample/ density of water
