Scientific Notation & Sig Figs
The number 3.68 x 104 has how many significant figures?
3 sig figs.
(Do not look at the scientific notation when establishing # of sig figs.)
In chemistry labs, this unit is most often used to measure volume of liquids.
What is the liter (L)?
Which of the following is a chemical change?
a) Evaporation of a puddle of water
b) Melting an ice cube
c) Baking a loaf of bread
d) Freezing water into ice
c) Baking a loaf of bread
New substances form during baking.
The subatomic particle that is negatively charged and orbits the nucleus
Electrons
The formula for sodium phosphate is:
Na₃PO₄
one phosphate ion (PO₄³⁻), which has a -3 charge, combines with three sodium ions (Na⁺), which each have a +1 charge
Use correct # of sig figs.
86.7426 – 17.3 =
69.4
If an object has a mass of 27 g and a volume of 9 mL, this is its density.
What is 3.0 g/mL?
Which of the following is a physical change?
a) A puddle of water evaporating
b) Iron rusting
c) Gasoline burning
d) Cookies baking
a) A puddle of water evaporating
Evaporation changes state, not composition.
The number of these particles determines an atom's identity as an element
Protons
The formula for sodium sulfate is:
Na₂SO₄
Na⁺ (charge +1) and SO₄²⁻ (charge –2) combine as Na₂SO₄.
use correct # of sig figs.
45.908 m + 12.34215 m + 0.9 m =
59.2 m
A temperature of 25 °C equals this many Kelvins.
What is 298 K? (25 + 273)
Distinguish between physical and chemical properties
(find the physical property; the others are chemical properties)
a) The tendency of iron to rust when exposed to oxygen
b) The density of gold
c) The reactivity of sodium with water
d) The ability of hydrogen to burn in air
b) The density of gold
Density is measurable without changing composition. (Study guide topic on physical vs. chemical properties.)
Atoms of the same element that have different numbers of neutrons
Isotopes
The name of N₂F₂ is:
dinitrogen difluoride
Two N and two F; use prefixes di- and di-
A ruler is usually 30 cm long. Express that distance in kilometer. Must use scientific notation.
100 cm = 1 m = 1x10-2 m
1 km = 1000 m = 1x103 m
Answer = 3 x 10-4 km
A liquid has a mass of 48.0 g and a volume of 60.0 mL. Express its density in kg/m³.
What is 800 kg/m³?
A metal block has a mass of 42.6 g and a volume of 11.3 mL. What is its density?
3.77 g/mL
42.6 / 11.3 ≈ 3.769 → 3.77 g/mL
The terms used to describe the weighted average mass of all isotopes of an element based on abundance
Atomic mass/Average atomic mass
The name of N₂Cl₂ is:
Two N and two Cl; use prefixes di- and di-
dinitrogen dichloride.
An ant travels a distance of 150 mm. Express that distance in kilometers.
1 mm = 0.001 m = 1x10-3 m
1 km = 1000 m =1x103 m
Answer = 1.5x10-4
How many cm3 are in 1.000 in3?
1 in = 2.54 cm
Answer: 16.39 cm3
Using 1 in = 2.54 cm, cube the conversion.
1 in3 = (2.54 cm)3 = 16.387 cm3
If a graduated cylinder contains 22.5 mL of water and the volume rises to 75.2 mL after dropping in an object of mass 6.25 g, what is the density of the object?
0.119 g/mL
ΔVolume = 75.2 − 22.5 = 52.7 mL
6.25 g / 52.7 mL ≈ 0.1186 → 0.119 g/mL.
Carbon-14 and Carbon-12 are isotopes. The difference between these is the number of...
Neutrons
What is the formula when Na⁺ combines with PO₄³⁻?
Na₃PO₄
Three Na⁺ needed to balance one PO₄³⁻