Matter is composed of
elements, compounds, and mixtures of the two
Matter is made of
mixtures and pure substances
Pure substances are made of
either pure compounds or pure elements
Pure substances are made of
either pure compounds or pure elements
A compound is a
~ substance that contains two or more elements combined in a fixed proportion ~ substance composed of two or more elements that are chemically bonded in a definite, fixed ratio by mass
An element is
~ the simplest form of matter that has unique properties and is composed of only one kind of atom ~ a chemical substance that contains only one kind of atom and that cannot be broken down into simpler substances
Elements contain
only one type of atom
Many elements do not occur as
pure substances on earth, but rather occur as parts of compounds
For example,
liquid mercury, composed only of mercury atoms, is a pure element but it is very rare in nature
compounds contain
more than one type of atom
A compound is a substance that contains
two or more elements combined in a fixed proportion
Examples of compounds include the following:
~ Water (H2O) as a solid, liquid, or gas is made of two atoms of hydrogen (H) and one atom of oxygen (O). ~ Sodium chloride (NaCl), or table salt, is composed of one atom of sodium (Na) and one atom of chlorine (Cl). ~ Calcium carbonate (CaCO3), or chalk, is a compound of calcium (Ca), carbon (C), and oxygen (O). It is found in seashells. ~ Ammonia (NH3) is the active ingredient in window cleaners and fertilizers, and is made of one nitrogen (N) and three hydrogen (H) atoms. ~ Sucrose (C12H22O11), a sugar, is a white solid naturally produced by plants and algae and is made of 12 carbon atoms (C), 22 hydrogen atoms (H), and 11 oxygen atoms (O).
separation procedures allow
you to tell the difference between various types of matter
separation procedures allow you
to tell the difference between various types of matter
how can you tell whether a given material is a pure substance, mixture, compound, or element?
1. Can the material be separated into parts by physical means, such as evaporating, freezing, or filtering? ~ Yes: It is a mixture. (Note: Some mixtures are hard to separate.) ~ No: It is a pure substance (go to Question 2). 2. Can the material be separated into parts by chemical means? ~ Yes: It is a compound. ~ No: It is an element.
cinnamon-flavored sugar can be
separated into its components
sugar is made of
complex chains of hydrogen, carbon , oxygen
burning is a
chemical process that breaks down sugar into carbon and water vapor
elements can be represented by
chemical symbols
many chemists over the ages used symbols to
represent the elements
modern chemists use
one - or two - letter symbols for elements
compounds can be represented by
chemical formulas
a compound can be
represented by combinations of symbols in a chemical formula
symbols
chemical symbols show the elements that are combined together in the compound. In sulfuric acid, hydrogen (H), sulfur (S), and oxygen (O) are bound together
subscripts:
subscripts show the number of atoms of each element that are present in the compound. If there is no subscript, then only one atom of that element is present. In sulfuric acid there are 2 hydrogen atoms, 1 sulfur atom, and 4 oxygen atoms combined together. So in a sulfuric acid molecule there are 7 atoms
coefficients:
coefficients show the number of molecules that you have; this will be important when you learn about chemical equations
mixtures
physical blend of two or more substances
your teacher gives you a black powder. When you dissolve the powder in water, you see red particles that float to the top, black particles that sink to the bottom, and a green liquid. Was the black powder a pure substance, mixture, element, or compound?
mixture
a molecule of ozone gas has three atoms of oxygen. Which of these describes ozone most specifically?
element
the chemical formula for sodium citrate is Na 3C 6H 5O 7. which of the following statements is true?
sodium citrate is a compound with a total of 21 atoms