Question

classify each substance as an element or a compound.
calcium
chalk
hydrogen
salt
water
carbon
chlorine
mercury
sodium
zinc
carbon
copper
oxygen
sugar
dioxide
elements
compounds

Explanation:

To classify substances as elements or compounds, we use the definitions: an element is a pure substance made of only one type of atom, while a compound is a pure substance made of two or more different types of atoms chemically bonded.

Elements:

• Calcium: Consists of only Ca atoms.
• Carbon (both entries): Consists of only C atoms.
• Chlorine: Consists of only Cl atoms.
• Mercury: Consists of only Hg atoms.
• Sodium: Consists of only Na atoms.
• Zinc: Consists of only Zn atoms.
• Copper: Consists of only Cu atoms.
• Oxygen: Consists of only O atoms.
• Hydrogen: Consists of only H atoms.

Compounds:

• Chalk (calcium carbonate, \( \text{CaCO}_3 \)): Made of Ca, C, O atoms.
• Salt (sodium chloride, \( \text{NaCl} \)): Made of Na, Cl atoms.
• Water (\( \text{H}_2\text{O} \)): Made of H, O atoms.
• Carbon dioxide (\( \text{CO}_2 \)): Made of C, O atoms.
• Sugar (e.g., \( \text{C}_{12}\text{H}_{22}\text{O}_{11} \)): Made of C, H, O atoms.

Answer:

Elements:

calcium, carbon, carbon, chlorine, mercury, sodium, zinc, copper, oxygen, hydrogen

Compounds:

chalk, salt, water, carbon dioxide, sugar

(Note: The table can be filled as follows:

Elements	Compounds