Atoms
This subatomic particle has a negative charge.
What is an electron?
This type of property does not depend on how much of a substance you have.
What is an intensive property?
In dimensional analysis, these are used to change a quantity from one unit to another.
What are conversion factors?
An atom has 17 protons, 18 neutrons, and 17 electrons. What is its mass number and charge?
Mass number = 35; charge = 0
Which measurement contains four significant figures: 0.00450 g, 4.050 g, 4500 g, or 40 g?
4.050 g
The number of these particles determines the identity of an element.
What are protons?
Mass and volume are examples of this type of property because they depend on the amount of substance present.
What are extensive properties?
Convert 4.50 × 10² mg to grams.
What is 0.450 g?
Two atoms have the same number of protons but different numbers of neutrons. What are they called, and what property is different between them?
Isotopes; their mass numbers are different.
A student measures a liquid as 25.0 mL and a mass of 19.8 g. What is the density of the liquid?
0.792 g/mL
An atom has 17 protons, 18 neutrons, and 17 electrons. Identify the element and its mass number.
What is chlorine-35?
Density is calculated using this equation.
What is density = mass ÷ volume?
A student walks at a rate of 1.25 m/s. How many kilometers would they travel in 45.0 minutes?
What is 3.38 km?
Setup:
1.25 m/s × 60 s/1 min × 45.0 min × 1 km/1000 m = 3.38 km
An ion has 16 protons, 18 electrons, and 17 neutrons. Identify the element, its charge, and its mass number.
Sulfur (S), 2− charge, mass number = 33.
Which of the following represents a chemical property rather than a physical property?
A. Copper has a density of 8.96 g/cm³
B. Copper melts at 1,085°C
C. Copper reacts with oxygen to form copper oxide
D. Copper can be shaped into thin sheets
C. Copper reacts with oxygen to form copper oxide
An ion has 12 protons and 10 electrons. What is its charge, and what element is it?
What is Mg²⁺ (magnesium ion)?
A sample has a mass of 78.4 g and a volume of 8.00 mL. What is the density of the sample, reported with the correct number of significant figures?
What is 9.80 g/mL?
Mercury has a density of 13.6 g/mL. What is the mass, in kilograms, of 2.50 L of mercury?
What is 34.0 kg?
Setup:
2.50 L × 1000 mL/1 L × 13.6 g/1 mL × 1 kg/1000 g = 34.0 kg
An atom contains 27 protons, 32 neutrons, and 25 electrons. What is the element, what is its mass number, and what is its overall charge?
Cobalt (Co), mass number = 59, charge = 2+.
A sample has a mass of 45.62 g and a volume of 12.4 mL. Calculate its density and report your answer with the correct number of significant figures.
3.68 g/mL
An atom has a mass number of 40 and contains 18 electrons. If the atom is neutral, identify the element and determine the number of neutrons.
What is argon, with 22 neutrons?
An unknown metal has a density of 7.85 g/mL. A sample of the metal has a mass of 156.0 g. What is the volume of the sample, reported with the correct number of significant figures?
What is 19.87 mL?
Work:
156.0 g × 1 mL / 7.85 g = 19.8726 mL → 19.9 mL
A car is traveling at 65.0 miles/hour. Convert this speed to meters/second using 1 mile = 1.609 km, 1 km = 1000 m, and 1 hour = 3600 seconds.
What is 29.1 m/s?
Setup:
65.0 mi/hr × 1.609 km/mi × 1000 m/km × 1 hr/3600 s
= 29.06 m/s → 29.1 m/s
An ion has a 2− charge and a mass number of 80. If the element has 34 protons, how many protons, neutrons, and electrons does the ion contain?
34 protons, 46 neutrons, and 36 electrons.
A student calculates the following:
12.5 g×1 g1000 mg=12500 mg
What is wrong with the final answer, and what should be changed?
The conversion is correct, but the answer should have 3 significant figures: 1.25 × 10⁴ mg.