MEDIUM
Lower Secondary Stage 8
IMPORTANT
Earn 100

Green copper carbonate powder was heated. The powder started bubbling and it turned black.

State two signs that a chemical reaction took place.

Important Questions on Chemical Reactions

MEDIUM
Lower Secondary Stage 8
IMPORTANT
Cambridge Lower Secondary Science Stage 8 : Student's book>Chapter 6 - Chemical Reactions>End of chapter review>Q 6
Green copper carbonate powder was heated. The powder started bubbling and it turned black. One of the products was gas. How can you tell? 
HARD
Lower Secondary Stage 8
IMPORTANT
Cambridge Lower Secondary Science Stage 8 : Student's book>Chapter 6 - Chemical Reactions>End of chapter review>Q 7
A piece of magnesium with a mass of 2.4 g was heated in air to form magnesium oxide with a mass of 4.0 g. Calculate the mass of oxygen that reacted with the magnesium.
EASY
Lower Secondary Stage 8
IMPORTANT
Cambridge Lower Secondary Science Stage 8 : Student's book>Chapter 6 - Chemical Reactions>End of chapter review>Q 8
Explain why combustion is an example of oxidation reaction.
MEDIUM
Lower Secondary Stage 8
IMPORTANT
Cambridge Lower Secondary Science Stage 8 : Student's book>Chapter 6 - Chemical Reactions>End of chapter review>Q 9
A carbonate was added to an acid to make a salt.potassium chloride. Write the word equation for this.
MEDIUM
Lower Secondary Stage 8
IMPORTANT
Cambridge Lower Secondary Science Stage 8 : Student's book>Chapter 6 - Chemical Reactions>End of chapter review>Q 10

Deep added an unknown compound (X) to some hydrochloric acid. Bubbles were formed.

Describe how he could find out if the gas was hydrogen or carbon dioxide.

MEDIUM
Lower Secondary Stage 8
IMPORTANT
Cambridge Lower Secondary Science Stage 8 : Student's book>Chapter 6 - Chemical Reactions>End of chapter review>Q 10
Deep added an unknown compound (X) to some hydrochloric acid. Bubbles were formed. He discovers that the gas is carbon dioxide.What does this show about compound X. 
MEDIUM
Lower Secondary Stage 8
IMPORTANT
Cambridge Lower Secondary Science Stage 8 : Student's book>Chapter 6 - Chemical Reactions>End of chapter review>Q 10
Deep added an unknown compound (X) to some hydrochloric acid. Bubbles were formed. He can not name compound X. Explain why.
MEDIUM
Lower Secondary Stage 8
IMPORTANT
Cambridge Lower Secondary Science Stage 8 : Student's book>Chapter 6 - Chemical Reactions>End of chapter review>Q 11

A teacher measured the mass of a piece of iron wool (fine strands of iron) as 3.6 g. She used tongs to hold the iron in a Bunsen flame. She noticed it turned darker and dull in colour. She let it cool and then measured the mass again. It was now 3.9 g.

Describe what happened to the mass of the iron when it was heated.