1. Mercury
   Nickel
2. Copper
   Gold

Mercury sulfide is a bright-red paint pigment that was used in the Paleolithic area. It is also known as cinnabar. Due to mercury sulfide's toxicity, the pigment is rarely used today.

1. Ammonia
   Vinegar
2. Bleach
   Water

Adult woman and adult men have different percentages of water in their bodies. Men are made up of approximately 60 percent of water, while women contain about 55 percent water.

1. Mixed
   Neutral
2. Negative
   Positive

Protons have 1,836 times the mass of an electron. They are found in all atomic nuclei.

1. Molecule
   Double Atoms
2. A Noble gas
   A halogen

Compounds are the smallest particle of a compound that retains the chemical properties of a compound. The atoms in a molecule may be held together by covalent bonds.

1. Radon
   Nickel
2. Polonium
   Uranium

An atom is radioactive when an unstable nucleus loses energy, resulting in the release of radiation. Elements with an atomic number 84 or higher are radioactive.

1. 10
   2
2. 1
   6

In a solid state, carbon dioxide is called dry ice. Carbon dioxide must be put under pressure at low temperatures in order to become dry ice.

1. Atomic number
   Chemical symbol
2. Relative atomic mass
   Chemical reactions

Chemical symbols do not always match up with the current scientific name. For example, sodium has the chemical symbol Na. Sodium, which is known as natrium in Latin, is one of many elements that kept the abbreviation for its Latin name.

1. Potassium
   Helium
2. Gold
   Carbon

An organic compound has carbon atoms covalent linked to other elements. However, there are some compounds that contain carbon, but are not classified as organic. Some examples are cyanides, carbonates, and carbides.

1. Freezing point
   Boiling point
2. Plasma point
   Solid point

Boiling points are determined using the air pressure at sea level. However, adding solutes or changing the pressure will affect the boiling point.

1. Mixture
   Solubility
2. Density
   Changeability

Masses of objects are compared to a platinum-iridium cylinder with a mass of one kilogram. The cylinder is called the International Prototype Kilogram. It is kept in Sèvres, France at the International Bureau of Weights and Measures.

1. Proton
   Electron
2. Neutron
   Free

In the periodic table, the number of protons and neutrons comprise the mass number. To get the number of neutrons, you subtract the number of protons from the mass number.

1. Solid
   Liquid
2. Gas
   Ice

There are four basic states of matter: solid, liquid, gas and plasma. Plasma is a gas that is positively charged as opposed to a regular gas which has an equal number of protons and neutrons.

1. Gold
   Potassium
2. Sodium
   Helium

Potassium makes up 2.4 percent of the Earth's crust by mass, making it the seventh most abundant metal there. Each year, mines extract about 35 million tons.

1. The atom has to gain or lose an electron and have an electric charge.
   The atom needs the same amount of electrons and protons.
2. The atom needs to gain or lose a neutron.
   The atom needs to bond with helium.

Electrolytes are substances that ionize in a solution. Examples of electrolytes include potassium, calcium, sodium and magnesium.

1. 1
   10
2. 7
   4

The pH scale is a logarithmic scale that goes from 1 to 15. The human body is close to neutral. It has a pH of approximately 7.4.

1. Atomic number
   Alphabetically
2. Size
   Solubility

Russian scientist Dmitri Mendeleev created the periodic table. He noticed a pattern in certain groups, so, in his version, he left gaps for elements that were unknown in his time.

1. Salt
   Steel
2. Water
   Pepper

Salt has many uses. It lowers the melting point of snow or ice. It is also can remove calcium and magnesium compounds from water.

1. Bleach
   Ammonia
2. Vinegar
   Water

Ammonia is used as a fertilizer and in the manufacture of synthetic fabrics. It is also used as a household cleaner.

1. Ionic
   Water
2. Covalent
   Metallic

A chemical bond is the attraction between two atoms, ions or molecules. They enable the formation of chemical compounds.

1. Potassium
   Sodium
2. Lithium
   Gold

One the periodic table, alkali metals make up the first group on the far left. In order from top to bottom, the alkali metals are lithium, sodium, potassium, rubidium, cesium and francium.

1. Gold
   Silver
2. Nickel
   Mercury

Silver is considered a precious metal. It also has the most electrical conductivity, which makes it useful in electrical circuits.

1. Hydrogen
   Gold
2. Sodium
   Plutonium

Deuterium is a rare from of hydrogen. It was discovered by Harold Urey in 1931. It has one proton and one neutron in its nucleus.

1. Mass
   Shape
2. Solid
   Gas

Bromine and mercury are the only elements liquid at standard temperature and pressure. Four other elements become liquid slightly above room temperature. They are cesium, Francium, Gallium and rubidium.

1. Xenon
   Krypton
2. Hydrogen
   Neon

Hydrogen is the lightest element. It is also highly flammable, but it needs an oxidizer and ignition source to cause a fire.

1. Speeds it up
   Slows it down
2. Makes it happen
   Prevents it from occuring

Many catalysts are enzymes, which naturally occur. There are also some solid catalysts, most of which are metals. Examples of catalysts are oxides and sulfides.

1. Radioactives
   Noble gases
2. Metals
   Halogens

There are seven noble gases. In order from top to bottom, they are helium, neon, argon, krypton, xenon, radon and oganesson.

1. Endothermic
   Exothermic
2. Interthermic
   Plasma

Exothermic reactions give off energy, which causes the surrounding area to feel warmer than before. Endothermic reactions cause the surrounding area to feel cold because it has absorbed the surrounding heat.

1. Rare
   Special
2. Universal
   Basic

Water holds the title "universal solvent" because it dissolves more substances than any other liquid. Water's ability to attach to both negative and positive compounds is why it is able to dissolve so many substances.

1. Acids
   Quarks
2. Molecule
   Atom

"Atom" comes from the Greek word for "uncuttable." While we now know that atoms are made of protons, electrons and neutrons, a Greek named Democritus believed that atoms could not be broken up smaller. The name stuck.

1. Half-life of an element
   Size of an element
2. Number of neutrons
   Number of protons

In an uncharged atom, the atomic number is also equal to the number of electrons in the atom. Neutrons have no impact on the atomic number. However, they do impact atomic mass.

1. 5
   100
2. 2
   15

Helium was first detected in the sun's corona. The element takes its name from the Greek word, "helios," which means sun.

1. An atom with the same number of protons as another, but a different number of neutrons
   An atom with the same number of electrons as another, but a different number of protons
2. The standard form of an element
   An atom with the same number of protons as another, but a different number of electrons

The word isotope comes from Greek. It is a combination of isos, which means "equal," and topos, which means "place."

1. Positive Ion
   Negative Ion
2. Neutral Ion
   Basic Ion

Ions have different names depending on their charge. A positively charged ion is called a cation. A negatively charged ion is called an anion.

1. Bases
   Acids
2. Baking Soda
   Neutrals

Litmus tests are used to determine whether a substance is a acidic or basic. A red result means the substance is an acid. A blue result means the substance is base.

1. Covalent
   Polar
2. Normal
   Metallic

Polar bonds are partly ionic, whereas covalent bonds have an equal sharing of electrons. Polar bonds occur between two nonmetal atoms that have different numbers of electrons.