Sig Figs & Unit Conversions
How many significant figures are in 0.0470?
3
Name this compound: NaCl
Sodium chloride
As you move left to right across a period, this property generally increases.
Electronegativity
Is melting ice a physical or chemical change?
Physical (No new substance was made)
What are the three states of matter?
Solid, Liquid, Gas
Divide 48.0 by 3.2 with correct sig figs.
15
Name this compound: N2O5
Dinitrogen pentoxide
Which has a larger atomic radius: Na or Cl? Explain why.
Na: fewer protons mean less pull on the outer electrons even though they are in the same period
Is burning wood considered a physical or chemical change?
Chemical (A new substance is made)
What is the difference between an element and a compound?
Element = one type of atom. Compound = two or more elements chemically combined
Convert 8.75 kilometers to millimeters.
8,750,000 mm
Name this acid: HNO3
Nitric acid
This element in period 2 breaks the expected trend by having a lower ionization energy than the element to its left.
Oxygen
A substance dissolves in water and can be recovered by evaporation. Chemical or physical?
Physical (composition unchanged)
What is a mixture? Give an example.
Two or more substances physically combined
Add 12.011 + 0.34 + 9.1.
21.5
Name this compound: Fe2(SO4)3
Iron(III) sulfate
Arrange these elements in order of increasing electronegativity: Ca, C, F, Al.
Ca < Al < C < F
What are two signs that a chemical change has occurred?
Color change, gas produced, precipitate formed, light/heat released, irreversible
What property describes how much mass is in a given volume?
Density (D = m/v)
Why does the number 100 have ambiguous significant figures, and how would you write it to clearly show 3 significant figures?
1.00 × 10² or 100.
Name this compound: Ca(H2PO4)2
Calcium dihydrogen phosphate
This element has the highest electronegativity, yet it has no defined electron affinity value.
Fluorine: it has no empty valence orbitals, and its electron affinity is technically unmeasurable by standard methods
Electrolysis splits water into H₂ and O₂. Chemical or physical change?
Chemical (new substances with different properties are formed)
Is air a pure substance or a mixture? Explain.
Mixture it contains N₂, O₂, Ar, CO₂, etc. in variable proportions