Changes in Materials Quiz 2

You are testing methods to clean a silver coin. What is the BEST example of a testable hypothesis?

• Cleaning coins is boring.

• Baking soda will clean the coin better than vinegar.

• Silver coins are better than copper ones.

• Old coins are more valuable.

What are the products of a neutralization reaction between hydrochloric acid and sodium hydroxide?

• Hydrogen and oxygen

• Salt and water

• Vinegar and baking soda

• Heat and gas

7. What is a sign that a chemical reaction is happening?

• You spill the liquid

• The solution is stirred

• A gas is given off

• The temperature stays the same

Why is repeating an experiment three times better than just two times?

• It uses more equipment

• It makes the experiment more fun

• 
  C. It gives more data to spot patterns and check for reliability

• It makes the reaction stronger

What result would best show that an acid has been neutralized?

• The liquid becomes fizzy

• The color of the indicator turns green

• The temperature increases

• The solution becomes thick

In an experiment to find out how the amount of baking soda affects the height of a reaction with vinegar, which part is the variable?

• The type of container used

• The amount of baking soda added

• The amount of vinegar used

• The room temperature

What are the main reactants in the experiment where tarnished silver is cleaned using science?

• Silver metal (Ag), aluminum foil (Al), baking soda (NaHCO₃) and water (H₂O)

• Silver sulfide (Ag₂S), aluminum foil (Al), baking soda (NaHCO₃), and water (H₂O)

• Silver oxide (Ag₂O), hydrogen gas (H₂), and baking soda (NaHCO₃)

• Aluminum sulfide (Al₂S₃), silver metal (Ag), and water (H₂O)

In the experiment where tarnished silver (covered in silver sulfide, Ag₂S) is cleaned using aluminum foil (Al), baking soda, and hot water, what are the main chemical products?

• Silver metal (Ag) and hydrogen gas (H₂)

• Aluminum sulfide (Al₂S₃) and silver metal (Ag)

• Silver oxide (Ag₂O) and sodium carbonate (Na₂CO₃)

• Sodium sulfide (Na₂S) and aluminum foil (Al)

In the experiment to clean tarnished silver using baking soda, hot water, and aluminum foil, why is the aluminum foil needed?

• It helps heat the water more quickly

• It reacts with silver to make it shinier

• It gives sulfur somewhere else to bond, helping remove the tarnish

• It scrubs the silver clean

In the silver cleaning experiment using aluminum foil (Al), baking soda (NaHCO₃), and hot water, why are bubbles sometimes seen?

• The silver reacts with water to make hydrogen gas

• Baking soda reacts with acids or impurities, making carbon dioxide gas

• The aluminum produces oxygen gas when heated

• The tarnish turns into gas when cleaned off the silver