Classifying States of Matter Flashcards
Why is it important to classify states of matter?
The classification allows us to speak a common scientific language and understand why substances have certain characteristics.
What is an element (simple definition)
Pure chemical substance consisting of one type of atom
What is the most abundant element in Earth’s crust?
Oxygen
What is an atom (simple definition)
Smallest particle of an element that retains the characteristic properties of that element
What is a compound (simple definition)
Pure chemical substance consisting of two or more different chemical elements
Chemical compounds have what type of chemical structure?
A unique and defined chemical structure
What are chemical compounds consisted of?
They consist of a fixed ratio of atoms that are held together in a defined spatial arrangement by chemical bonds
What are molecular compounds held together by?
Covalent bonds
What are salts held together by?
Ionic bonds
What is a molecule?
Electrically neutral group of at least two atoms in a definite arrangement that retains the composition and chemical characteristics of a compound
What are salts composed of?
Composed of electrically charged ions that are arranged in extended 3D networks
Definition of an atom
The smallest particle of an element that has the properties of that element and can enter into a chemical combination
What is one of the smallest things we can see with our unaided eyes?
A single thread of a spider web
True or False: It is rare to find collections of individual atoms
True
True or False: Only a few elements consist of a collection of individual atoms that move about independently of each other
True
Which elements consist of a collection of individual atoms that move about independently of each other?
Helium, Neon, and Argon
Give an example of common elements that consists of units that have pairs of atoms?
Hydrogen, Nitrogen, Oxygen, and Chlorine
Definition of molecule
Consists of two or more atoms joined by strong forces called chemical bonds
What are chemical bonds?
Strong forces that join two or more atoms together
True or False: A molecule can consist of two or more identical atoms
True
True or False: A molecule can consist of two or more different atoms
True
How do we represent molecules?
We use chemical symbols and subscripts to indicate how much of each atom is present.
When displaying molecules, chemists typically use what?
A color scheme as a coding system to determine which elements are being used and displayed.
What are two broad categories that we can classify matter into?
Pure substances and mixtures
What is a pure substance?
Substances with a constant composition where all specimens have exactly the same makeup and properties
True or False: We can divide pure substances into two categories
True
What are the two categories that we can divide pure substances into?
Elements and compounds
What is an element?
Pure substances that cannot be broken down into simpler substances by chemical changes
What are some common/familiar examples of elements?
Iron, silver, gold, aluminum, sulfur, oxygen, and copper
About how many elements make up about 99% of the Earth’s crust and atmosphere
11
True or False: A majority of elements on Earth are found in chemical combinations with other elements
True
True or False: About 1/4 of the elements on earth are found in the free state
True
What is a compound?
Pure substances that can be broken down by chemical changes
The breakdown by chemical changes can produce
A. Elements
B. Compounds
C. Both
D. All of the above
D. All of the above
Are the properties of combined elements different from those in the free, or uncombined, state?
Yes
What is a mixture?
A composition of two or more types of matter that can be present in varying amounts and can be separated by physical changes
What is a heterogeneous mixture?
A mixture with a composition that varies from point to point
Are homogeneous mixtures and solutions the same thing?
Yes
What is a homogenous mixture?
A uniform composition that appears visually the same throughout
What is a solution?
A uniform composition that appears visually the same throughout
What are some examples of homogenous mixtures?
Air, maple syrup, saltwater, vinegar, and gasoline
What are some examples of heterogenous mixtures?
Salad, soil, mixed nuts, oil and water, ice cubes in a drink, rocks in sand, and muddy puddle.
How can water be broken down?
Water can be broken down into hydrogen and oxygen gases by the addition of energy
What does the breakdown of water involve?
A rearrangement of atoms in water molecules into different molecules
Is oxygen flammable?
No, but is it required for combustion of a fuel
Is hydrogen flammable?
Yes, it is highly flammable and a potent energy source
The characteristics that enable us to distinguish one substance from another are called?
Properties
What is a physical property?
A characteristic of matter that is not associated with a change in chemical composition
What are some examples of physical properties?
Density, color, hardness, melting and boiling points, and electrical conductivity.
True or False: Melting and freezing temperatures can only be observed as matter undergoes a physical change
True
What is a physical change?
A change in state or properties of matter without any accompanying change in its chemical composition (the identities of the substances contained in the matter)
What are some instances where we observe a physical change occurring?
Wax melting, sugar dissolving into coffee, and steam condensing into liquid water
What is crucial to understanding physical change vs. chemical change?
Physical changes involve a change in the physical state/form/properties of the substance, but there is no change in the chemical composition
What is a chemical property?
The change of one type of matter into another type of matter (or the inability to change)
What are examples of chemical properties?
Flammability, toxicity, acidity, reactivity, and heat of combustion
How do we identify a chemical property?
We look for a chemical change
What is a chemical change?
A change that always produces one or more types of matter that differ from the matter present before the change
What are some examples of chemical changes?
The formation of rust, all forms of combustion (burning), and food being cooked/digested or rotting
True or False: Properties can be used to sort elements into three classes
True
What are the three classes that elements can be sorted into?
Metals, nonmetals, and metalloids
What are metals?
Elements that conduct heat and electricity well
What are nonmetals?
Elements that poorly conduct heat and electricity
What are metalloids?
Elements that have properties of both metals and nonmetals
How does an element different from a compound? How are they similar?
An element cannot be divided further, but a compound can since it contains more than two elements. Both can be very abundant naturally and can be classified as pure substances.
How do molecules of elements and molecules of compounds differ? In what ways are they similar?
Molecules of elements contain only one type of atom while molecules of compounds contain two or more types of atoms. They are similar in that both are comprised of two or more atoms chemically bonded together.
True or False: Compounds consists of atoms of two or more different elements
True
True or False: A particle can be classified as an element or molecule, but not both
False
Classify the following as an element or compound
A. Copper
B. Water
C. Nitrogen
D. Sulfur
E. Sucrose
F. A substance composed of molecules each of with contains two iodine atoms
A. Element
B. Compound
C. Element
D. Element
E. Compound
F. Element
A sulfur atom and sulfur molecule are not the identical. What is the difference?
A sulfur molecule is multiple atoms of sulfur
How are molecules in oxygen gas, the molecules in hydrogen gas, and water molecules similar? How do they differ?
In each case, a molecule consists of two or more combined atoms. They differ in that the types of atoms change from one substance to the next.
Classify each of the following changes as physical or chemical changes
A. Condensation of steam
B. Burning of gasoline
C. Souring of milk
D. Dissolving of sugar in water
E. Melting of gold
A. Physical
B. Chemical
C. Chemical
D. Physical
E. Physical
The volume of a sample of oxygen gas changed from 10 mL to 11mL as the temperature changed. Is this a chemical or physical change?
Physical change
A 2.0 L volume of hydrogen gas combined with 1.0 L of oxygen gas to produce 2.0 L of water vapor. Does oxygen undergo a chemical or physical change?
Chemical change
Which of the following statements are true of hydrogen gas (H2)?
A. H2 is an element
B. H2 is an atom
C. H2 is a compound
D. H2 is a molecule
E. H2 is an ionic salt
A, D
Which of the following statements are true of water (H2O)?
A. H2O is an element
B. H2O is an atom
C. H2O is a compound
D. H2O is a molecule
E. H2O is an ionic salt
C, D
Which of the following statements are true of table salt (NaCl)?
A. NaCl is an element
B. NaCl is an atom
C. NaCl is a compound
D. NaCl is a molecule
E. NaCl is an ionic salt
C, E
Which of the following statements are true of neon (Ne)?
A. Ne is an element
B. Ne is an atom
C. Ne is a compound
D. Ne is a molecule
E. Ne is an ionic salt
A, B
