Science Chapter 2.1
Why are elements and compounds classified as pure substances?
A pure substance is matter that always has exactly the same composition.
How do mixtures differ from pure substances?
An element is a substance that cannot be broken down into simpler substances.
1.Which of these groups of letters could be used as a symbol for an element? a.HF b.Cm c.Car d.fe
B
1.Which of these substances is a compound? a.copper b.water c.oxygen d.carbon
B
1.Which of the following statements does not apply to a compound? a.It is made of two or more elements. b.It has components that are joined in fixed proportions. c.It can be separated into components by physical methods. d.It can be broken down into elements or other compounds.
C
1.How does a compound differ from a mixture? a.A compound cannot be broken down into simpler substances. b.Compounds can be separated by physical processes and mixtures cannot. c.The composition of a mixture cannot vary. d.A compound is made of two or more elements in fixed proportion.
D
An element has a fixed composition because it contains only one type of atom.
No two elements contain the same type of atom.
How do mixtures differ from pure substances?
The properties of a mixture can vary because the composition of a mixture is not fixed.
What is the main difference among solutions, suspensions, and colloids?
The size of the particles in a mixture has an effect on the properties of the mixture.
Solutions
When substances dissolve and form a homogeneous mixture
Suspensions
a heterogeneous mixture that separates into layers over time.
Milk
colloid
Colloids
contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension.
pure substance
is matter that always has exactly the same composition.
Windshield wiper fluid
solution
Muddy water collected from a swamp
suspension
Heterogeneous Mixtures
the parts of the mixture are noticeably different from one another.
Homogeneous Mixtures
the substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another.
