Understanding Density, Mass, and Volume

• Density is the amount of matter contained within an amount of space, equal to mass divided by volume and measured in g/cm³ or g/mL.
• Mass is the amount of matter in an object, measured in units like grams, kilograms, milligrams, or pounds.
• Volume is the amount of space an object occupies, measured in units like mL, L, cm³, or m³.
• Density is a physical property.
• Density = Mass/Volume
• Mass = Volume/Density
• Volume = Mass/Density
• kg is a unit for mass
• cm³ is a unit for volume
• g/mL is a unit for density
• m³ is a unit for volume
• mL is a unit for volume
• g is a unit for mass
• kg/L is a unit for density
• Density of an object with a mass of 200 g and a volume of 50 cm³ is 4 g/cm³.
• Volume of a gold bar with a density of 19 g/cm³ and a mass of 9500g is 500 cm³.
• Mass of an aluminum piece with a density of 2.6 g/cm³ and a volume of 15 cm³ = 39g.
• The volume of cricket ball with a density of 0.8g/cm³ and a mass of 165 g is 206.25 cm³.
• The density of a cube with a side length of 8 cm and a mass of 960 g is 1.875g/cm³.
• The density of a cylinder with a mass of 128 g, a radius of 4 cm and a height of 9 cm is0.28 g/cm³
• Density of an irregular object with a mass of 60.0 g, that displaces water from 75.0 mL to 90.5 mL is 3.9 g/mL
• Ice floats on water because it is less dense, which is a special property of water (H2O).
• Determine the density of an irregularly shaped object by measuring the mass using a scale, finding the volume using water displacement (V = VF-V1), and calculating density using the formula = m/v.
• An object's density will decrease if its mass stays the same but its volume increases
• A rock is denser than a sponge with the same volume because it has more mass.
• The formula for calculating density is mass/volume.
• If an object has a mass of 50 g and a volume of 10 cm³, its density is 5 g/cm³.
• Gold is the densest of the following materials: water, air, gold, and wood.
• If an object sinks in water, its density is greater than the density of water.
• The density of a substance decreases when its temperature increases, assuming it expands.
• If an object is cut in half, its density stays the same.
• A piece of wood floats on water because its density is lower than water
• When two liquids with different densities are combined, the denser liquid sinks below the less dense liquid.
• True: Density is defined as mass divided by volume.
• False: Objects with higher density than water always float.
• False: Two objects with the same volume must have the same density.
• True: An object's density can change if its temperature changes.
• True: The unit g/cm³ is commonly used for solids.
• False: A balloon filled with helium rises because helium is denser than air.
• True: Gases are less dense than liquids.
• True: If an object is compressed, its density increases.
• True: Density can help identify unknown substances.
• False: Ice is denser than liquid water.
• Density is mass divided by volume.
• Volume is the amount of space an object occupies.
• Mass is the amount of matter in an object.
• Buoyancy is the ability of an object to float.
• Water displacement is used to find the volume of an irregular object.
• An object with lower density than the surrounding fluid will float and an object with a density greater will sink.

Periodic Table of Elements

• In an atom of sodium, protons = electrons = 11, and neutrons = 12.
• Groups are vertical columns and periods are horizontal rows on the periodic table.
• Noble gases do not easily react with other substances.
• Noble gases: Helium and Neon never react, while others have to be forced to.
• Metals are shiny and hard, malleable and ductile, and good conductors
• Nonmetals are not shiny and soft, not malleable or ductile, and bad conductors.
• The number of neutrons in an atom equals atomic mass minus the atomic number.
• Elements are arranged in increasing atomic number instead of atomic mass because there were frequent discrepancies with the table when organized by atomic mass.
• Organization according to atomic number eliminates the discrepancies.
• Dmitri Mendeleev formulated the periodic table, and arranged it by atomic mass and predicted elements that didn't exist.
• Henry Moseley discovered the atomic number and the number of protons in the nucleus.
• Each box of the periodic table includes the element name, chemical symbol, and atomic mass.
• The atomic number of an element represents its number of protons.
• Oxygen has the chemical symbol O.
• The rows in the periodic table are called Periods.
• Elements in the same group have the same properties.
• Francium is in Group 1 and is the most reactive metal.
• Noble gases are in Group 18.
• The atomic mass of an element is determined by the number of protons and neutrons.
• Carbon (C) has 6 electrons.
• Iron (Fe) is a metal.
• True: All elements in Group 18 are gases at room temperature.
• False: Elements in the same period have the same number of electrons.
• False: The periodic table is arranged by increasing atomic mass.
• True: Metals are found on the left side of the periodic table.
• True: The halogens (Group 17) are highly reactive nonmetals.
• False: The atomic mass is always a whole number.
• False: Electrons are found in the nucleus of an atom.
• True: An element's chemical symbol is always one or two letters.
• True/False: Hydrogen is a metal (it's in group 1 with metals, but it is a gas).
• True: The number of protons equals the number of electrons in a neutral atom.
• Atomic number designates the number of protons in an atom.
• Atomic mass stands for: Total number of protons and neutrons in an atom.
• Vertical columns on the periodic table are called Groups.
• Horizontal row on the periodic table are called Periods.

Properties of Elements

• Alkali metals are highly reactive metals.
• Alklai earth metals are very reactive nonmetals.
• Noble Gases are in Group 18, and known for being unreactive.
• The periodic table organizes all known elements.