CHEM 151 EXAM 1 QUESTIONS AND VERIFIED
ANSWERS
What are chemists' three central goals and what kind of questions should be asked? -
Answers - Analysis- What is this?
Synthesis- How do I make it?
Modeling- How do I explain it?
intensive property - Answers - DO NOT depend on the amount of material
Melting point, boiling point, density, color
CHARACTERISTIC
of a material
extensive property - Answers - Depend on the amount of material
Length, Mass, Area
Independent of the type or identity of the material
Tell you HOW MUCH
quantitative - Answers - any value recorded directly from a tool is considered
quantitative data (numbers based)
qualitative - Answers - It includes such descriptions as color as well as observations
about texture changes and anything else that is actually an opinion (try describing the
difference in color between two different blades of grass)
significant figures rules - Answers - 1. Zeroes in the beginning of a number never count.
2. Zeroes at the end of a number count only if there is a written decimal point.
3. The digits 1 - 9 always count.
4. Zeroes between the digits 1 - 9 always count.
matter - Answers - anything that has mass and occupies space
substance - Answers - that object which has mass and occupies space
composition - Answers - the makeup of something (components)
state - Answers - its physical form/condition
three states of matter - Answers - gas, liquid, solid
solid - Answers - -atoms or molecules pack close to each other in fixed locations
-vibrate but do not move around or past each other
-fixed volume and shape
, crystalline - Answers - case in solid state where atoms or molecules are in patterns with
long-range, repeating order ex) salt and diamond
amorphous - Answers - case where a solid's atoms or molecules do not have any long-
range order. ex.) glass and plastic
liquid - Answers - atoms or molecules pack about as closely as they do in solid matter
however they are free to move relative to each other, giving liquids a fixed volume but
not a fixed shape.
-assume shape of container
gas - Answers - atoms have a lot of space between them and are free to move relative
to one another making gases compressible
-always assume volume and shape of their container
pure substance - Answers - a substance made of only one kind of matter and having
definite properties
mixture - Answers - a substance consisting of two or more substances mixed together
(not in fixed proportions and not with chemical bonding)
-heterogenous
-homogenous
homogenous mixture - Answers - same throughout
heterogenous mixture - Answers - composition varies throughout (ex. wet sand);
disproportional
elements - Answers - a molecule composed of one kind of atom; cannot be broken into
simpler units by chemical reactions.
compound - Answers - a substance made up of atoms of two or more different elements
joined by chemical bonds (fixed, definite proportions)
Central Goals and Questions - Answers - Detection:
Does the sample contain substance X?
Identification:
What is the identity of the substance in this sample?
Separation:
How can the substances present in the sample be separated?
Quantitation:
How much of substance X is in the sample?
Three different perspectives - Answers - macroscopic, microscopic, symbolic
ANSWERS
What are chemists' three central goals and what kind of questions should be asked? -
Answers - Analysis- What is this?
Synthesis- How do I make it?
Modeling- How do I explain it?
intensive property - Answers - DO NOT depend on the amount of material
Melting point, boiling point, density, color
CHARACTERISTIC
of a material
extensive property - Answers - Depend on the amount of material
Length, Mass, Area
Independent of the type or identity of the material
Tell you HOW MUCH
quantitative - Answers - any value recorded directly from a tool is considered
quantitative data (numbers based)
qualitative - Answers - It includes such descriptions as color as well as observations
about texture changes and anything else that is actually an opinion (try describing the
difference in color between two different blades of grass)
significant figures rules - Answers - 1. Zeroes in the beginning of a number never count.
2. Zeroes at the end of a number count only if there is a written decimal point.
3. The digits 1 - 9 always count.
4. Zeroes between the digits 1 - 9 always count.
matter - Answers - anything that has mass and occupies space
substance - Answers - that object which has mass and occupies space
composition - Answers - the makeup of something (components)
state - Answers - its physical form/condition
three states of matter - Answers - gas, liquid, solid
solid - Answers - -atoms or molecules pack close to each other in fixed locations
-vibrate but do not move around or past each other
-fixed volume and shape
, crystalline - Answers - case in solid state where atoms or molecules are in patterns with
long-range, repeating order ex) salt and diamond
amorphous - Answers - case where a solid's atoms or molecules do not have any long-
range order. ex.) glass and plastic
liquid - Answers - atoms or molecules pack about as closely as they do in solid matter
however they are free to move relative to each other, giving liquids a fixed volume but
not a fixed shape.
-assume shape of container
gas - Answers - atoms have a lot of space between them and are free to move relative
to one another making gases compressible
-always assume volume and shape of their container
pure substance - Answers - a substance made of only one kind of matter and having
definite properties
mixture - Answers - a substance consisting of two or more substances mixed together
(not in fixed proportions and not with chemical bonding)
-heterogenous
-homogenous
homogenous mixture - Answers - same throughout
heterogenous mixture - Answers - composition varies throughout (ex. wet sand);
disproportional
elements - Answers - a molecule composed of one kind of atom; cannot be broken into
simpler units by chemical reactions.
compound - Answers - a substance made up of atoms of two or more different elements
joined by chemical bonds (fixed, definite proportions)
Central Goals and Questions - Answers - Detection:
Does the sample contain substance X?
Identification:
What is the identity of the substance in this sample?
Separation:
How can the substances present in the sample be separated?
Quantitation:
How much of substance X is in the sample?
Three different perspectives - Answers - macroscopic, microscopic, symbolic
