CHEMICAL REACTIONS AND EQUATIONS

What happens in a chemical reaction?

• Bonds between atoms break and/or are formed

• New atoms are created and/or removed

• Protons move from one atom to another

• Electrons change into protons

Which of the following would indicate that a chemical reaction has occurred?

• A new element has been created

• A different substance has formed

• The total mass has either increased OR decreased

• The total number of elements has either increased OR decreased

BEFORE the equation is balanced, how many Hydrogen atoms are present on the reactant side?

• 6

• 2

• 12

• 8

How many sulfur atoms are present in this molecule?

• 4

• 3

• 12

• 1

What does the Law of Conservation of Mass state?

• No new substances can be made or destroyed

• No new compounds can be made or destroyed

• No new atoms can be made or destroyed

• Mass cannot be lost from a physical reaction

Which of the following follows the Law of Conservation of Mass?

• CH₄ + 2 O₂ → 2CO₂ + 2 H₂O

• 2 CH₄ + 2 O₂ → CO₂ + 4 H₂O

• CH₄ + 2 O₂ → CO₂ + 2 H₂O

• All the above

In a chemical reaction, ________________________ are changed into _______________________.

• Reactants; Products

• Electrons; Molecules/Compounds

• Coefficients; Subscripts

• Original Elements; New Elements

Bacteria in milk causes it to curdle over time. What type of change is this?

• Chemical

• Physical

• Both

• Neither

Which type of reaction pulls in thermal energy from the environment around it?

• Endothermic

• Exothermic

Which of the following is not a physical change?

• (a) Boiling of water to give water vapour

• (b) Melting of ice to give water

• (c) Dissolution of salt in water

• (d) Combustion of Liquefied Petroleum Gas (LPG)