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57 terms

Pure Substances & Mixtures

Chapter 2-Section1
STUDY
PLAY
chemistry
the study of matter and its changes
Chemists explore
the makeup, properties, changes, and interactions of matter
anything that has mass and takes up space
matter
Examples of things that are not matter
light, sound, electricity
There are ____ elements.
114
There are _____ naturally occurring elements.
92
several elements are
synthetic, created by a scientist
what is the most abundant element in the human body?
oxygen
element
a substance that cannot be broken down into a simpler substance
elements are ___________ of matter.
building blocks
Each element is made up of
one kind of atom.
Each element is represented by
a one, two, or three letter symbol that is used worldwide.
atom
the smallest unit of an element that maintains the chemical properties of that element.
atoms join together to form
molecules
molecule
a group of atoms held together by chemical forces
Most molecules are made of
atoms of different elements, but some are made of atoms of the same element.
compound
a substance made up of atoms of two or more different elements joined by chemical bonds in a fixed proportion
example of a compound
water
hydrogen peroxide has
two hydrogen atoms, 2 oxygen atoms
carbon dioxide has
1 carbon atom, 2 oxygen atoms
carbon monoxide
1 carbon atom, 1 oxygen atom
Every compound is ________________ from the elements it contains.
unique and different.
Compounds have
chemical formulas
Chemical formulas
shows how many atoms of each element-a unit of a substance.
number in front of the chemical formula is the number of
molecules
pure substance
any matter that has a fixed composition and definite properties
Pure substances are NOT
mixtures.
Pure substances include
elements and compounds.
examples of pure substances.
water, sugar, salt
mixture
a combination of two or more substances that are not chemically combined and do not have a fixed composition
heterogeneous mixture
components are not evenly distributed and components can be distinguished
homogeneous mixture
components are evenly distributed and appear the same throughout
liquids that are not carbonated can also contain gases. The foam on top is a
gas-liquid mixture.
compounds have a
set proportion of elements by weight, separated by chemical means.
mixtures are separated by
physical means.
suspension
a mixture in which particles of a material are more or less evenly disperse throughout a liquid or a gas
A property of a suspension is that the
particles settle out of the mixture when it is allowed to stand
The particles in most suspensions are about the size of a
bacteria cell.
Suspension particles are large enough to be
filtered out of the mixture.
decanting
the process of pouring a less dense liquid off of a denser liquid
colloid
a mixture consisting of tiny particles that are intermediate in size between those in solutions and those in suspension, and that are suspended in a liquid, gas, or solid
the particles in a colloid are smaller than those in a
suspension
Colloid particles do not
settle out of the mixture. they remain spread throughout.
emulsion
a colloid in which liquids that usually do not mix are spread throughout each other
emulsifier
coats one of the immiscible liquids allowing the immiscible liquids to spread throughout each other
All homogeneous mixtures are
solutions.
solute
the substance that dissolves in the solvent
solvent
the substance in which the solute dissolves.
What is the universal solvent
water
A mixture of liquids can form a
solution
One way to separate miscible liquids is by the process of
distillation
distillation separates
miscible liquids that have different boiling points
A mixtures of gases can form a
example:
solution
air
Alloys
a homogeneous mixture of 2 or more metals
What are three examples of alloys?
bronze, brass, and steel
Amalgam solution
Mercury is dissolved into solid silver.
Many common solutions are solids dissolved in
liquids