Counting Atoms

Coal contains carbon and other elements. Carbon dioxide forms when coal burns in the presence of oxygen. Which of these is the best evidence that a chemical reaction occurs when coal burns?

• The shape of the coal changes
• Oxygen is present
• A new substance is produced
• Coal is made up of more than one element

Which of these is NOT a sign of a chemical reaction?

• A phase change

• Formation of a precipitate

• A color change

• A temperature change

The red numbers in the image below represent ________

• subscripts
• coefficients
• I don't know, and don't want to try
• None of the answers are correct

• 1

• 2

• 3

• 4

A teacher is demonstrating physical and chemical changes to her class. Which action should she use to demonstrate a chemical change?

• cutting a piece of paper
• folding a piece of paper
• tearing a piece of paper
• burning a piece of paper

A precipitate is...

• a solid that has formed

• a reactant in a reaction
• a clear substance
• the mass of a product

How many atoms of hydrogen are in

C₆H₁₂O₆

• 6

• 12

• 18

• 2

Rust on an iron fence

• Chemical Change
• Physical Change

Glass bottle that is shattered

• Chemical Change
• Physical Change

Which is the correct formula for:
 three hydrogen (H)
one sulfur (S)
four oxygen (O)

• H₃SO₄
• HSO₄
• H₄S₃O
• H₂O