accurate description of a theory, chemistry homework help
QUESTION 1
Which of the following is an accurate description of a theory?
a well-tested explanation for how something works.
an observation made over and over again.
someone’s idea about how something works.
easily proved wrong and therefore cannot be trusted in science.
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QUESTION 2
Which of following statements is true about scientific knowledge?
Scientific ideas are not subject to change, and so knowledge stays the same.
Scientific knowledge is constantly evolving as new observations are made.
While scientific knowledge increases over time, old knowledge never changes.
Theories can change frequently, but scientific knowledge is absolute.
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QUESTION 3
Which of the following is an example of pure research?
Determining the causes of dementia in elderly people.
Creating robots to walk on the surface of Mars.
Colliding subatomic particles at high speeds to see what they form.
Working with alloys to determine the lightest carbon fiber composition for armor.
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QUESTION 4
Which of the following institutions employs scientists?
Hospitals
Universities
Corporations
All of the above
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QUESTION 5
If the flame of a Bunsen burner should accidentally go out, a student should immediately run over to the teacher and inform him/her.
TRUE
FALSE
2 points Save Answer
QUESTION 6
In terms of eye safety in the lab:
Students do not need to wear safety goggles if they already have prescription glasses on.
Students need to wear safety goggles at all times, regardless if they have prescription glasses or not.
Students only need to wear safety goggles if they do not have their own prescription glasses or if they have contacts.
Goggles only need to be worn if the chemicals used in a lab are liquids or solutions.
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QUESTION 7
You observe that a liquid has decreased volume by 23.4 milliliters (mL) during the duration of an experiment. What is this type of observation?
quantitative
qualitative
indirect observation
a physical change
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QUESTION 8
It is equally accurate to measure volumes with a beaker as with a graduated cylinder.
TRUE
FALSE
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QUESTION 9
When measuring the volume of a liquid in a graduated cylinder, you should raise the cylinder up to eye level to read the meniscus more accurately.
TRUE
FALSE
2 points Save Answer
QUESTION 10
To accurately measure the volume of a typical liquid in a graduated cylinder, what should you do?
look at the bottom part of the meniscus
look at the top part of the meniscus
average the top and bottom parts of the meniscus
ignore the meniscus and determine which mL line the liquid is closest to
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QUESTION 11
To accurately measure out 35 milliliters of liquid, you should use:
a 10-mL glass pipette several times
a 50-mL beaker
a 25-mL graduated cylinder two times
a 50-mL graduated cylinder one time
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QUESTION 12
Two groups complete an experiment requiring the mass measurement to be repeated three times in the experiment. Group I selects a single member of the group to measure the mass. Group II allows any person of the group to measure the mass once, so they will be done more quickly. At the end of the experiment, the results for group I are closer to the actual than the results of group II. Explain why this might be.
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5 points Save Answer
QUESTION 13
Which of the following would be considered the most heterogeneous mixture?
oil/vinegar salad dressing
pasteurized milk
vinegar
olive oil
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QUESTION 14
Which of the following pairs forms a homogenous mixture after being mixed together?
sand and water
salt and water
oil and water
oil and vinegar
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QUESTION 15
Which of the following is an example of a physical change?
Rusting bicycle chain
Melting butter
Fireworks exploding
Baking a cake
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QUESTION 16
Which of the following is an example of a physical change?
Separating sand from gravel
Baking a pie
Burning a piece of paper
Rusting
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QUESTION 17
Of the following examples, select those that represent a chemical change.I. Water freezing and changing into iceII. Leaves changing color in the fallIII. Mixing lemonade mix powder with waterIV. Milk going sour
II, III, IV
I, II, III, IV
II, IV
I, II
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QUESTION 18
Which of the following is an example of a chemical property?
Flammability
Boiling point
Density
Elasticity
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QUESTION 19
A mixture of sand and iron filings can be separated into its individual components by using a magnet.
TRUE
FALSE
2 points Save Answer
QUESTION 20
Which of the following is NOT a method used to physically separate components in a mixture?
chromatography
sublimation
distillation
precipitation
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QUESTION 21
The best way to separate ethanol from its solution in water is to use which of the following?
chromatography
precipitation
distillation
filtration
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QUESTION 22
The standard (Bohr) model of the atom shows that:
a positively charged nucleus has negatively charged particles surrounding it
a neutrally charged nucleus has neutrally charge particles encompassing it
a negatively charged nucleus has positively charged particles encompassing it
a positively charged nucleus has positive or negatively charged particles encompassing it
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QUESTION 23
An atom has no electrical charge because:
its subatomic particles have no electrical charges
the positively charged neutrons cancel out the negatively charged electrons
the negatively charged neutrons cancel out the positively charged protons
there are as many positively charged protons as negatively charged electrons
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QUESTION 24
The atomic number represents the total number of protons and neutrons in an atom.
TRUE
FALSE
2 points Save Answer
QUESTION 25
Electrons exist only outside of the nucleus.
TRUE
FALSE
2 points Save Answer
QUESTION 26
Pick the correct statement for the following isotope: 42Ca
42 is the mass number and 20 is the atomic number.
42 is the number of neutrons and 20 is the number of protons.
42 is the number of protons and 20 is the number of electrons.
42 is the atomic number and 20 is the number of neutrons.
3 points Save Answer
QUESTION 27
In structure, the standard (Bohr) model of the atom is most similar to
plum pudding
our solar system
chocolate chip cookie dough
the Milky Way galaxy
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QUESTION 28
Most of the volume of an atom is contained:
in the protons
in the nucleus
in the neutrons
in the empty space around the nucleus
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QUESTION 29
In comparing two isotopes of the same element, the atomic number:
changes to reflect the number of protons.
changes to reflect the new mass number.
changes to reflect the number of new neutrons.
stays the same.
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QUESTION 30
If the number of protons for an element changes, then:
the element turns into an isotope
the element becomes a different element
the number of electrons for that element changes as well
the number of neutrons changes as well
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QUESTION 31
Use the information for the isotopes of element X to calculate the average atomic mass of X, and identify the element.
Isotope Abundance Mass (amu)
35X 75.77% 34.969
37X 24.23% 36.965
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QUESTION 32
Which of the following statements about subatomic particles best characterizes protons?
positive charge, heavy, found in the nucleus of an atom
no charge, heavy, found in the nucleus of an atom
negative charge, light, circling the nucleus of an atom
no charge, light, circling the nucleus of an atom
3 points Save Answer
QUESTION 33
Henry Moseley determined that, with a few exceptions, the order of increasing atomic number is the same as increasing atomic mass.
TRUE
FALSE
2 points Save Answer
QUESTION 34
Who was the first person to organize the elements so that properties of undiscovered elements could be predicted?
J.W. Dobereiner
Dmitri Mendeleev
JJ Thomson
Ernest Rutherford
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QUESTION 35
Generally, when going from left to right across a period on the periodic table:
atomic radii decrease
ionic radii increase
electronegativity decreases
valence electron number decreases
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QUESTION 36
In the periodic table, alkali metals are situated:
At the extreme left side.
At the extreme right side.
Towards the middle of the periodic table.
Directly next to the right of the stair steps/metalloids.
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QUESTION 37
Generally, when going down columns 1 or 2 of the periodic table, the reactivity of elements:
increases
decreases
remains the same except for noble gases
remains the same except for halogens
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QUESTION 38
Which of the following classifications is NOT correct?
Group 1 and Group 2 – Metals
Group 7 – Halogens
Group 8 – Noble Gases
Group 5 – Metalloids
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QUESTION 39
Which of the following classifications is NOT correct?
Noble gases – 8 valence electrons
Halogens – 6 valence electrons
Transition metals – number of valence electrons varies
Alkali Rare Earth metals – 2 valence electrons
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QUESTION 40
The chemical symbol for lead is La.
TRUE
FALSE