Atoms, Molecules, Compounds & Water Properties

Hydrogen is a pure substance represented by the chemical symbol H. Which of the following best describes hydrogen?

• Hydrogen is an element made of two or more kinds of atoms.

• Hydrogen is a compound made of only one kind of atom.

• Hydrogen is a compound made of two or more kinds of atoms.

• Hydrogen is an element made of only one kind of atom.

The element oxygen, represented by the symbol O, is classified as

• a pure substance

• a compound

• a mixture

• a solution

Carbon (C) and hydrogen (H) are pure substances. Each is made of only one type of atom, but carbon atoms are different from hydrogen atoms. Carbon and hydrogen chemically combine to form methane (CH4).

• methane is an element and carbon and hydrogen are compounds.
• carbon, hydrogen, and methane are all elements.
• carbon, hydrogen, and methane are all compounds.
• carbon and hydrogen are elements and methane is a compound.

What is a compound?

• an atom with more electrons than protons

• a substance in which the atoms of two or more elements are combined together

• an atom with more neutrons than protons

• a substance in which the atoms of three or more elements are combined together

The chemical combination of two or more different kinds of atoms in fixed amounts is called a(n)

• orbit
• compound
• mixture
• element

What part of the atom is responsible for determining an atom's chemical properties?

• all electrons

• protons

• neutrons

• valence electrons

What property of water allows it to be such a versatile solvent that it is often called the "universal solvent?"

• Purity

• Polarity and cohesion

• High heat capacity

• Expansion upon freezing

Water striders can walk across the surface of calm water. Their feet push the surface of the water down slightly, but they do not break the surface. Why?

• The insects are light enough so they do not break the hydrogen bonds holding the water molecules together

• The insects actually use their wings to hover slightly above the water’s surface and they only skim it with their feet.

• The insect’s feet are non-polar, so they are repelled by the polar water molecules and are pushed away from the water’s surface.

• The insects are small enough to see the individual water molecules, so they are able to step carefully from one molecule to the next

What two elements make up water?

• Helium and oxygen
• Hydrogen and oxygen
• helium and carbon
• oxygen and carbon

Tags

NGSS.MS-PS1-1

What word describes when water is attracted to other substances?

• cohesion
• adhesion
• capillary action
• surface tension