#9.# The number of significant figures in #70.60# #"mph"# is #4#.

The number of significant figures in any number is really how many digits it contains.

One thing to bear in mind is that if the number begins with a #0#, it should not be counted towards the number of significant figures.

For example, #0.35# has #2# significant figures, but #3.50# has #3# significant figures.

Answer: (D)

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#10.# In order to find percent error, we can use this formula: #frac(|"Experimental value " - " actual value"|)(|"Actual value"|) times 100%#

#Rightarrow "Percent error" = frac(|9.53 " g / cm"^(3) - 9.78 " g / cm"^(3)|)(|9.78 " g / cm"^(3)|) times 100%#

#Rightarrow "Percent error" = frac(|- 0.25 " g / cm"^(3)|)(|9.78 " g / cm"^(3)|) times 100%#

#Rightarrow "Percent error" = frac(0.25 " g / cm"^(3))(9.78 " g / cm"^(3)) times 100%#

#Rightarrow "Percent error" = 0.02556237219 times 100%#

#therefore "Percent error" approx 2.5 %#

Answer: (B)

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#11.# In this question, we need to find the density of the green jade sample.

The density of any object is the quotient of its mass and volume, i.e. #"density" = frac("mass")("volume")#.

We already have the mass of the jade sample #(5.25# #"g")#, but we need to find its volume.

The graduated cylinder was initially filled with #50.0# #"ml"# of water, but after placing the sample in it, the water level rose to #60.5# #"ml"#.

The difference between these two volumes is the volume of the jade sample:

#Rightarrow "Volume of jade sample" = 60.5# #"ml"# #-# #50.0# #"ml"#

#therefore "Volume of jade sample" = 10.5# #"ml"#

Now, let's use plug all relevant values into the density formula:

#Rightarrow "Density of jade sample" = frac(5.25 " g")(10.5 " ml")#

#therefore "Density of jade sample" = 0.50# #"g / ml"#

Answer: (A)

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#12.# The first question asks us to assess which substance #underline("cannot")# be drawn into a wire.

A substance's property of being drawn into a wire is known as ductility.

According to the table, sulfur is #underline("not")# ductile, so it #underline("cannot")# be drawn into a wire.

Answer: (B)

The second question asks about the unification of two elements: copper and oxygen.

Whenever two different elements are chemically combined, they form compounds.

So "when copper and oxygen chemically unite, they form" - a compound.

Answer: (B)