Intro to Chemical Reactions

Which of the following is a sign that a chemical reaction has occurred?

• change in shape
• melting
• formation of a gas
• dissolving

Which of the following describes a precipitate?

• a liquid forms when a block of metal is heated
• a solid forms when one liquid is poured into another
• a gas forms when a solid is placed in a liquid
• bubbles form when an acid is poured on a rock

A white baking soda solution was combined with white calcium chloride. Once combined the temperature increased, the substances bubbled, and were white in color. What indicators of a chemical change were shown?

• Temperature increase
• Color change
• Bubbling/fizzing
• Temperature increase and bubbling/fizzing

What is a coefficient?

• The small number on the right of the chemical symbol.
• The large number to the left of a formula.

Why must chemical equations be balanced?

• So that the equation doesn't explode

• The reaction won't happen until it is balanced

• Based on the Law of Conservation of Matter, matter cannot be created or destroyed.

• Based on the Law of Conservation of Energy, energy cannot be created or destroyed.e

2Ca + O₂ > 2CaO 

What is the 2 located behind oxygen (O) called?

• coefficient
• reactant
• subscript
• product

Consider the chemical equation CH₄ + 2 O₂ → CO₂ + 2 H₂O. In this equation, CH₄ is a

• product
• reactant
• displacement

Which of the following is NOT a chemical property?

• state of matter

• photosensitivity

• combustability

• flammability

In a chemical reaction, (aq) written after a compound means that:

• the compound is flammable.

• the compound is dissolved in water.

• the compound will melt.

• the compound is unstable.

Changing the subscript in a chemical formula changes _______.

• nothing

• the identify of the substance so that it becomes a different compound

• the electrical charge on the atoms of that substance

• the amount of that substance