Which statement describes a chemical property of water ?
answer
Under the proper conditions, water will breal apart into hydrogen and oxygen gas.
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A science student wants to use distillation to separate a mixture of two substances in the liquid state. For the student to be successful, which property should be significantly different between the two liquids?
answer
Boiling point
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A student is measuring the properties of a sample of ethanol. Which is an extensive property of the sample?
answer
Mass
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Which statement describes a physical change
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A sculpture cast a statue in molton bronze and allows it to harden
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Is the freezing of mercury in reversible or irreversible physical change
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It is reversible because solid mercury can be melted to form liquid mercury again
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A few spoonfuls of sugar crystals are mixed thoroughly until dissolved into water. Classify this mixture
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A homogeneous mixture of a solid and a liquid
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Which set is an example of an element, a compound, and a mixture
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Nitrogen, table sugar, cough syrup
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What is identified by the chemical formula C6H12
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A compound made of two elements
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How are compounds different from elements
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Compounds can be broken apart by chemical means into simpler substances but elements cannot
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How can you distinguish a pure substance from a mixture
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A pure substance has a fixed composition; a mixture has a composition that may vary
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In a chemical reaction how does the mass of the reactants compare with the mass of the products
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The total mass of the products always equals the total mass of the reactants
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When a chemical change is taking place, which change can often be observed
answer
All of the above
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A horizontal row of the periodic table is usually referred to as a
answer
period
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A golf ball has more mass than a tennis ball because it
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Contains more matter
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How do you vapors and gases differ?
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Generally, a gas is in the gaseous state at room temperature and a vapor is in either the solid-state or liquid state at room temperature.
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Which of the following can be classified as a mixture?
answer
Pure air
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Which of the following is a heterogeneous mixture?
answer
soil
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An example of a homogeneous mixture is
answer
Stainless steel
question
Which of the following is true about compounds?
answer
They are substances
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Determine the number of significant figures in this measurement: 11 soccer players
answer
Unlimited
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Three measurements are each close to one another, but differ greatly from the accepted, correct value for the measurement. Which of the following best describes these measurements?
answer
They have good precision, but poor accuracy
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What is the number of significant figures in the measurement 5.00 cubic meters?
answer
3
question
What temperature units do scientist commonly used
answer
Degrees Celsius and kelvins
question
What is the volume of a paperback book 21CM tall, 12 CM wide, and 3.5 CM thick?
answer
8.8 * 10^2 cm^3
question
Which of the following shows the correct conversion of 170°C to Kelvin's?
answer
443 K
question
What is the density of helium in grams per liter?
answer
1.7...
question
How does the density of each piece compared to the density of the original gold bar
answer
The density of each piece equals to be density of the original bar
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Thermal substances, how does the density of a substance vary with temperature
answer
Density decreases with temperature
question
What is the speed of light in kilometers/hour?
answer
1.08 * 10^9
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What is the number of significant figures in the measurement 0.070 020 m?
answer
5
question
A measurement is accurate when it is
answer
Very close to the excepted value for the measurement
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In the measurement 0.503 L, which digit is the estimated digit?
answer
3
question
What is the measurement 111.009 mm rounded off to four significant digits?
answer
111.0 mm
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The weight of an object
answer
depends on its location
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Because the atomic mass of hydrogen is 1.0079 amu, what can be concluded about the two isotopes?
answer
Hydrogen-1 is by far the more abundant isotope
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What is the average atomic mass of the element?
answer
10.81 amu
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How did Democritus characterize atoms?
answer
as indivisible and indestructible.
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How does the Rutherford model describe the structure of atoms ?
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A dense, positively charged nucleus surrounded by negatively charged electrons
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What did Thomson contribute to atomic theory?
answer
The discovery of negatively charged particles now called electrons
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How do you calculate the number of neutrons in an atom ?
answer
Subtract the atomic number and the mass number
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What does the number represent and platinum - 194?
answer
The mass number of the isotope
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The isotopic composition of boron in nature is 19.9% and 80.1%. Using isotopic composition, calculate the atomic mass of the element boron
answer
10.8 amu
question
How is atomic number different from mass number?
answer
Atomic number equals the number of protons; mass number equals the number of protons and neutrons
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Which is one reason why the atomic masses of elements are generally not whole numbers?
answer
The atomic mass of an element is the weighted average of the masses of its isotopes
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Which of the following was originally a tenet of Dalton's atomic theory, but had to be revised about a century ago?
answer
Atoms are tiny indivisible particles
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Which of the following is true about subatomic particles
answer
The mass of a neutron nearly equals the mass of a proton
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Which is a useful rule for writing electron configurations ?
answer
An atomic orbital may describe a most two electrons
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What does the quantum mechanical model determine about electrons in atoms?
answer
An electrons allowed energy levels and the likelihood of finding it in various locations
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How can electrons in an atom move from one energy level to another?
answer
By gaining or losing just the right amount of energy, or a quantum
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Which is not one of the three rules for writing the electron configurations of elements?
answer
Law of conservation of energy
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In Bohr's model where are the electrons and protons located
answer
The electrons move around the protons, which are at the center of the atom
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How does the energy of an electron change when the electron moves closer to the nucleus?
answer
It decreases
question
The principal quantum number indicates what property of an electron?
answer
energy level
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