(b) Huiting wanted to find out the hardness of two materials H and F. She used a
rounded object made of material G and forced it into each material with the
same force. The results of her experiment are shown below.
rounded object of
material G
rounded object
of material G
3 mm
1 mm
object of
material H
object of
material F
List materials F, G, H in increasing order of hardness. Explain your answer.
[2]

law of conservation of matter

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.