Knewton Review Questions

The characteristics of atoms are responsible for the following aspects of a type of matter, EXCEPT: a. color b. density c. monetary value d. luster

c. monetary value

A ____________ consists of atoms of two or more different elements bound together.

compound

Which of the following is NOT a substance made of one type of molecule. a. carbon dioxide b. glucose c. water d. a cell

d. a cell A cell is a collection of many different types of molecules.

A mixture is made up of two or more: a. elements b. compounds c. pure substances d. any of the above

d. any of the above Any combination of the above will be considered a mixture, there simply must be at least two components.

The elements hydrogen (H) and oxygen (O) combine to create hydrogen peroxide (H2O2), which is a pure substance that can only be broken down by chemical means. Hydrogen peroxide is BEST defined as a(n) _______________. a. mixture b. solution c. element d. compound

d. compound Hydrogen peroxide is a compound because it is a pure substance that can only be broken down by chemical means. Hydrogen peroxide is not a mixture or a solution because it is a pure substance. Hydrogen peroxide is BEST defined as a compound, because it contains more than one element.

Which gas is most prevalent in the atmosphere?

nitrogen

How many atoms are present in a water molecule?

3

The smallest unit of matter that is indivisible without utilizing a nuclear reaction is known as: a. an atom b. a molecule c. a mixture d. a compound

a. an atom The atom is the smallest unit of an element. Molecules, mixtures, and compounds can be broken down into smaller constituents with relative ease.

A pure substance that can be broken down by chemical changes is known as a:

compound

Which element is most prevalent on earth?

hydrogen

What is the origin of the oxygen gas that makes up about 21% of the atmosphere?

photosynthesis

Which of the following elements CANNOT be extracted directly from air? a. nitrogen b. argon c. krypton d. chlorine

All of the choices are gaseous elements under standard conditions, but chlorine is too reactive to exist for long in elemental form in the air. Chlorine is produced from the electrolysis of sodium chloride. The other choices are stable gases with enough concentration in the atmosphere to be extracted from the air without a chemical reaction.

What is the difference between iron found inside of the core of the earth and on the surface/crust of the earth?

Iron in the core is mostly in a reduced state, while iron in the crust is mostly found in the oxidized state.

One amu is _________ the mass of one carbon-12 atom.

1/12

Who was the first to propose the idea of atoms?

Democritus

When are trailing zeros considered to be significant?

If the number has a decimal point, then all trailing zeros are significant. For example 3200., 320.0 and 0.03200 are all numbers that have two non-zero digits and two significant trailing zeros, for a total of four significant digits. If there is no decimal point, as in 3200, then the trailing zeros are considered either ambiguous or not-significant (opinions vary), but never considered to be significant.

What is the difference in the state of iron found in the core and iron found naturally in the crust?

Iron in the core is mostly in a reduced state, while iron in the crust is mostly found in the oxidized state. The core is composed of mainly of iron and nickel in their elemental states, which is the reduced form. The iron in the crust is mostly found in the oxidized form Fe2O3.

The portion of Earth's crust represented by the oceans and seas is called the __________.

The hydrosphere is the part of the crust containing water (the prefix hydro- means "water)".

When reading a measurement from an analog instrument like a ruler or a mercury thermometer, how should you determine the number of significant figures to record?

The least significant figure should be estimated by reading between the smallest markings on the instrument. It is only feasible to estimate one digit further than the precision inherent in the instrument, so if a ruler has centimeters, we can estimate tenths of a centimeter, but no more than that. The last digit should be estimated in this fashion, because the least significant digit in a measured number is treated as uncertain.

What is the precise mass of the proton?

The mass of the proton is slightly more than 1 amu, but not quite the mass of the neutron. The atomic mass unit is defined to be roughly the same as one proton or neutron, but precise masses of individual atoms cannot be calculated by summing the individual protons and neutrons. Instead 1 amu is defined to be exactly 112 the mass of a carbon-12 atom, and the masses of individual protons and neutrons are slightly larger than 1 amu. The proton has a mass of 1.00727 amu

Calcium carbonate deposits in Earth's crust are the result of __________.

ancient marine animals

Elements consist of only one type of ___________.

atom

Which of the following measurements would be a reasonable guess for the diameter of a gold atom? a. 3×10^8 m b. 3×10^−10 m c. 3×10^5 m d. 3×10^−3 m

b. 3×10^−10 m Atoms are microscopic particles that require specialized microscopes to visualize. Of the four lengths presented, only 3×10−10 m fits this description. The next shortest length, 3×10−3 m, is equal to 3 millimeters and can be seen by the naked eye.

Oil and water is an example of a: a. homogeneous mixture b. heterogeneous mixture c. pure substance d. compound

b. heterogeneous mixture Oil and water are separate compounds, so pure substance and compound are incorrect. In addition, oil and water will not mix evenly, so this is an example of a heterogeneous mixture.

Which of the following can be broken down into elements by chemical means? a. an element b. an atom c. a compound d. a mixture

c. a compound

Which of the following statements about atoms and molecules are true? a. all substances are composed of molecules. b. chemical bonds hold molecules of a substance together. c. all molecules are composed of atoms. d. all substances are held together by chemical bonds.

c. all molecules are composed of atoms; a molecule is defined as two or more atoms joined by strong forces called chemical bonds

Which of the following CANNOT be classified as a compound? a. carbon dioxide b. sodium chloride c. lithium d. sugar

c. lithium Lithium is an element. The rest are made of multiple elements.

The smallest particle of an element can be split into smaller components by what kind of process? a. a physical process b. a chemical process c. melting d. none of the above

d. none of the above The smallest particle of an element is an atom, and it cannot be split into its components by either a physical or chemical change. Splitting an atom is a nuclear process.

An atomic nucleus:

has a mass that is less than the sum of the masses of its protons and neutrons The mass of an atomic nucleus will always be less than the sum of the masses of the protons and neutrons contained within it, by a quantity known as the mass defect.

Which of the following is/are the smallest particle(s) of a substance that can exist independently without changing the substance itself? Select all that apply. a. compound b. molecule c. atom d. neutron

molecule and atom

_______ are compounds or mixtures that can be used as economical sources of elements. Most elements that can be obtained from the Earth exist as _________.

ores

Elements and compounds are considered to be what type of substances?

pure substances

The digits in a measurement, including the uncertain last digit, are known as:

significant figures

A homogeneous mixture is also called a:

solution We will often refer to homogeneous mixtures, especially in liquid form, as solutions. A homogeneous mixture doesn't necessarily have to be a liquid, and mixtures can't be pure substances such as a single compound.

A compound can be split into elements by what kind of process?

through a chemical process

True or False?: The neutron has slightly more mass than the proton, and much more mass than the electron.

true