chem quiz 1
what are the 3 ways scientists differ from other nonscience disciplines?
(1) they test ideas by experimentation, (2) they organize their findings in particular (often mathematical) ways, (3) they try to explain why things happen
what is the law of mass conservation?
-the total mass of substances does not change during a chemical reaction -Matter is neither created or destroyed in chemical reactions
Identify the exact numbers. 2.54 cm (the number of centimeters in exactly 1 in) 3 lbs (the weight of an object measured on a scale) 4 choices (the number of choices in this list) 56.00 s (a time measured by a stopwatch)
2.54 cm (the number of centimeters in exactly 1 in) 4 choices (the number of choices in this list)
what is a mixture?
A group of two or more elements or compounds that are physically intermingled. Mixtures do not have the same composition in every sample.
Ethanol, an organic solvent, has a density of 0.789 g/mL. Which of the following substances will float in ethanol? A. Ice which has a density of 0.917 g/mL B. 16.37 g of hexane which has a volume of 25.00 mL C. Aluminum which has a density of 2.7 g/mL D. 203 g of mercury which has a volume of 15.0 mL
B. 16.37 g of hexane which has a volume of 25.00 mL
Choose the correct statement regarding elements in the periodic table: A.Hydrogen is best described as a noble gas. B.Bromine is a period 4 halogen. C.Magnesium is a metal in group 3. D.Vanadium is an alkaline earth metal.
B. Bromine is a period 4 halogen
A certain substance can be easily compressed to fully occupy any container, regardless of its shape or volume. This substance is best classified as a: A. Solid B. Liquid C. Gas D. None of these
C. Gas
Choose the false statement about a compound: A .A pure substance can be classified as a compound. B.Two or more different elements are chemically combined to form a compound C.A compound can be separated using only physical means. D.The subscripts in a chemical formula of a compound indicate how much of each element is present.
C.A compound can be separated using only physical means.
give an example of a physical change
Change of state. (Solid to liquid)
A measurement within a data set is said to have good precision if it A. agrees closely with an accepted standard value. B. has a small number of significant figures. C. has a large number of significant figures. D. agrees closely with other members in the data set.
D. agrees closely with other members in the data set
Which of the following classification of matter is incorrect? A.Copper -an element B.Cough syrup-homogeneous mixture C.Carbon dioxide (CO2) -compound D.Unfiltered salt water -pure substance
D.Unfiltered salt water -pure substance
T/F breaking chemical bonds releases energy
FALSE, breaking chemical bonds does NOT release energy
what are the diatomic molecules? (how do we remember them)
H2, N2, O2, F2, Cl2, Br2, I2 (have no fear of ice cold beer)
what is a pure substance?
Has the same composition, does not vary from sample to sample, and it can't be separated physically into separate components.
can elements be broken down?
NO, elements cannot be broken down into any simpler substances by physical or chemical means
what is the law of definite proportions?
No matter the source, a particular compound is composed of the same elements in the same mass ratios
give an example of a chemical change
Pen is tarnishing and burning of gasoline
what is an element?
Simplest type of substance with unique physical and chemical properties.- consists of only one type of atom- cannot be broken down by physical or chemical means.
Which of the changes are chemical changes? Sugar is dissolved in water. A warm soda bottle fizzes when opened. The copper roof turns green over time. Baking soda is dissolved in vinegar and bubbles form. A fog appears on the windshield in cold weather.
The copper roof turns green over time. Baking soda is dissolved in vinegar and bubbles form.
what is a compound?
Two or more different elements which are chemically combined.-can be broken down by chemical means
what part of john daltons 4 postulates has been proven wrong?
We now know that atoms can be divided into smaller bits called protons, neutrons, and electrons
The universe tends toward _______ energy possible
`lowest
H20- 2H and 1o is an example of
a compound
define mass
a measure of the amount of matter in an object
Does the value reflect the true value?
accuracy
which are examples of matter? energy, sound, air, water, or heat
air and water
______- mixtures of medals
alloys
what is the scientific method?
an approach to asking questions and seeking answers that employs a variety of tools, techniques and strategies
Which of the statements describes a chemical property? Mercury is a liquid at room temperature. Water freezes at 0 ∘C.0 ∘C. Titanium is less dense than iron. Antacid tablets neutralize stomach acid.
antacid tables neutralize stomach acid
what must be formed for a reaction to be considered a chemical change?
at least one new substance must form, but will often be more than one
______ are the simplest form of matter that cannot be broken into any smaller pieces and still retain its properties
atoms
________ properties: can only be measured by changing the identity of the substance
chemical
potential energy is what form of energy?
chemical
________-the scientific study of matter, its properties, its transformations, and the qualitative and quantitative and energetic changes associated with those transformations
chemistry
_______- a substance composed of two or more different elements which are chemically bound together in a fixed ratio
compounds
gas to liquid is
condensation
what does a mixture consist of?
consists of two or more pure substances and may vary in composition
Which of the following is a chemical property of water? A. Density B. Boiling point C. Appearance D. None of these
d. none of these
gas to solid phase (frost) is known as _____
deposition
__________ theory of _______ _______: proposes the explanation that gravity is a result of the curvature of spacetime
einsteins theory of general relativity
pure substances contain ______ and _______
elements and compounds
_______ change- absorbs energy
endothermic change
______ is the capacity to do work or transfer heat
energy
the ability to do work is known as
energy
what is the first law of thermodynamics?
energy cannot be created or destroyed
_______ numbers- values for which there is no uncertainty that have defined values
exact numbers
______ change- releases energy
exothermic change
_________ properties depend on the amount of substance present
extensive
volume, mass, how much light is absorbed are all _____ properties
extensive properties
the total energy of the universe is _________
fixed
anything that has ______ and occupies _____ , and can be matter
has mass and occupies space
what is a pure substance?
has the same composition throughout and from sample to sample. It cannot be separated into components by physical means.
a _________ is a tentative explanation that has not been tested
hypothesis
what is the law of multiple proportions?
if elements A and B react to form two compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers
exact numbers have ____ significant figures
infinite
_________ properties do not depend of the amount of the substance present
intensive
density, color, and temperature are all _______ properties
intensive properties
Thermal energy is what form of energy?
kinetic
_______ energy- the energy of motion
kinetic
_____ is the measure of quantity of matter
mass
density is the ratio of an objects ____ to its _____
mass to volume
______- the physical material of the universe
matter
Zeros to the right of nonzeros with no decimal (47,000,000 kg)
maybe significant
__________ consist of two or more non-metal atoms chemically bound together (not just simply mixed)
molecules
what do mixtures contain?
more than one element substance
Zeros to the left of all nonzeros (000023 L or 0.0031 mg)
not significant
Which of these mixtures are heterogeneous? oil and water granite (a type of rock with multicolor spots) salt and water brass (an alloy of copper and zinc)
oil and water granite with multicolor spots
Significant figures are the digits in any measurement that are known with certainty, plus ...
one uncertain digit
_______ properties: properties of a substance that can be measured without changing the identity of the substance (dutility, shininess, boiling temperature)
physical
_______ energy- energy that is stored
potential
how finely are the measurements made?
precision
water, gold, and diamond are all examples of
pure substances
matter can be broken down into ______ and ______
pure substances and mixtures
_____ error is an error originating from uncontrollable variables in an experiment
random
forming bonds will always ______ energy
release energy- exothermic
breaking bonds will always _______ energy
require energy- endothermic
_______ ______ -a statement that describes observations that are true in widely varying circumstances (they just say WHAT is observed to be true, not why)
scientific law
_______ ________ are a combination of scientific theories and laws used to explain an observation and make testable predictions about a system
scientific models
non zeros Zeros between nonzeros Zeros after the decimal point after nonzero
significant
______ _______ allow us to communicate how precise a measurement is
significant digits
solid to gas phase is known as ____
sublimation
_______ _____ show the relative proportions of the elements in a compound
subscript numbers
_______ error is an error originating from controllable variable in an experiment
systematic
define volume
the 3D space that substances contain
What is kinetic energy? the energy from moving charged particles the energy of an object's motion and position the energy of an object in motion the energy stored due to an object's position or state
the energy of an object in motion
what was democritis the first to propose?
the idea of atoms
a _______ is an idea supported by a large body of experimental evidence (they say WHY/ HOW something occurs)
theory
T/F matter can be classified by its chemical composition
true
T/F pure substances cannot be separated by physical means
true
true or false: matter can be classified by its chemical composition
true
The last digit in a measurement is always ______ AND there can be only one ______ digit recorded in a measurement
uncertain
___________ is the amount of space a substance occupies
volume
can compounds be broken down by chemical means?
yes, compounds can be broken down by chemical means
