Atoms, Molecules, Pure Substances, &

Mixtures

CRCT PrepPart I

A scientist combines oxygen and hydrogen to form water. This combination illustrates that water is

A. an atom.B. an element.C. a mixture.D. a compound.

Copper is an element that is used in electrical wires. What is the smallest unit of copper that still maintains the characteristics of copper?

A. the atomB. the electronC. the nucleusD. the proton

What is the smallest particle of the element gold (Au) that can still be classified as gold?

A. atomB. moleculeC. neutronD. proton

Which of the following illustrations represents a pure substance?

A. B.

C. D.

Which formulas represent compounds?

A. O2, H2O2

B. CO2, H2O

C. H2, CO2

D. H2, O2

If different kinds of atoms are represented by different colored dots, which picture represents a sample of a compound?

A. B.

C. D.

If different kinds of atoms are represented by different colored dots, which picture below represents a mixture?

A. B.

C. D.

Which of the following is a compound?

A. oxygenB. waterC. nitrogenD. air

A mixture of powdered iron and sulfur reacts chemically when heated. What will be formed?

A. a single elementB. two other elementsC. a solutionD. a compound

A solution in a dish contains 3.0 grams of salt dissolved in 100 grams of water. If 50 grams of the water evaporate, the solution is

A. a compound.B. a mixture.C. an element.D. a solid.

Carbon dioxide is

A. an element.B. a compound.C. a solution.D. a mixture.

A chemical change combining two elements results in

A. an atom.B. a compound.C. an element.D. a mixture.

Atoms, Molecules, Pure Substances, &

Mixtures

CRCT PrepPart II

John has a mixture of salt, sand, and iron filings. To remove the iron filings from the mixture, John should

A. run a magnet through the mixture.

B. put the mixture in water and stir it.

C. throw the mixture into the air and see which material fall first.

D. blow on it and keep what does not blow away.

Which of the following elements is part of the chemical formula for table salt?

A. NaB. SiC. SD. O

When mud and water are combined, the result is

A. a mixture.B. a compound.C. an element.D. a molecule.

Which symbolizes a molecule of a compound?

A. HeB. BeC. N2

D. NaCl

Which of the following is an element?

A. airB. saltC. waterD. oxygen

Putting sand and salt together makes

A. a compound.B. an element.C. a mixture.D. a solution.

Plastic, wood, and iron are all made up of

A. cells.B. atoms. C. carbon.D. plants.

Water is

A. a compound.B. an element.C. a solution.D. a mixture.

An atom is to an element, as a molecule is to a

A. metal.B. nonmetal.C. metalloid.D. compound.

All of the substances on the periodic table are classified as elements because they

A. are pure substances.B. are composed of atoms.C. cannot be broken down

into other substances.D. cannot be dissolved in

water or other liquids.

Salt (NaCl) is a common substance. Salt is which of the following?

A. atomB. elementC. compoundD. mixture

Atoms, Molecules, Pure Substances, &

Mixtures

CRCT PrepPart III

Oxygen and hydrogen atoms combine to form water.

When one oxygen and two hydrogen atoms combine, what forms?

A. a different atomB. a different elementC. a moleculeD. a neutron

The smallest part of matter that is identifiable as an element is the

A. atom.B. molecule.C. cell.D. compound.

Several centuries ago, men called alchemists tried to transform common metals into gold. Even though they tried many different chemical and physical methods, they never succeeded because

A. they could not heat common metals to extremely high temperatures.

B. the common metals they worked with were not pure.

C. they did not add the correct material to the common metal.

D. elements cannot be changed to other elements by physical or chemical means.

Which picture illustrates the structure of a molecule of water?

A. B.

C. D.

Which of the following is best classified as a mixture?

A. carbon dioxideB. waterC. soilD. iron

A substance made up of two or more elements that have been chemically combined is called

A. an atom.B. a compound.C. an element.D. a mixture.

Because zinc can combine with other substances but cannot be changed into a simpler substance by an ordinary chemical process, zinc is classified as

A. a compound.B. a mixture. C. an element.D. an acid.

In the chemical formula for ammonia, NH3, what does the subscript 3 represent?

A. The number of nitrogen and hydrogen atoms in each molecule of ammonia.B. The number of hydrogen atoms in each molecule of ammonia.C. The number of ammonia molecules that will bond together.D. The number of nitrogen atoms in each molecule of ammonia.

A mixture of iron filings and sulfur can easily be separated by

A. placing the mixture in water.

B. performing a chemical reaction.

C. heating the mixture.D. using a magnet.