This document discusses pure substances and mixtures. It defines a pure substance as matter that has definite chemical and physical properties, and can be either an element or a compound. An element is a pure substance made of one type of atom that cannot be separated by physical or chemical means. A compound is a pure substance composed of two or more elements joined by chemical bonds. A mixture is a combination of two or more pure substances that are not chemically combined and can be separated physically. Mixtures can be either homogeneous or heterogeneous.
3. Pure Substances
A portion of matter that has definite chemical and physical
properties.
carbon dioxide (CO2), water (H2O),
nitrogen dioxide (NO2)…
4. One kind of pure substance:
Elements
Pure substance formed by one type of atom that cannot be
separated into simpler substance by physical or chemical means
• Ex. Physical means: distillation, filtration…
• Ex. Chemical means: chemical reaction: substitution, reduction…
Its symbol in the periodic table is its chemical formula
5. Other kind of pure substance:
Compounds
Pure substance composed of two or more different
elements joined by chemical bonds.
Has a chemical formula with at least two different letter.
Can only be separated by chemical procedures, not physically.
6. Mixtures
A combination of two or more pure substances that are not
chemically combined.
Each substance retains its properties in the mixture and has
his own chemical formula.
They can be separated physically.
There are two types: homogeneous and heterogeneous, depending
on the capacity of distinguish the different components or
not.
7. Can you identify the following?
You are going to see a series of photos. Say if each photo
represents an element, compound, or mixture.
Review:
An element is a pure substance which contains just one
type of atom.
A compound is a pure substance which contains two or
more different atoms joined together.
A mixture contains two or more different substances that
are only physically joined together, not chemically.
36. exercises
1)Complete the statements in your notebook:
a)
b)
c)
d)
e)
f)
g)
A mixture is a group of two or more …………….
All pure substances have a constant chemical ………..
A mixture can be separated by ……………. means
A pure substance like a compound can be separated by
………… means
An element is a pure substance composed by one type of
……….
A heterogeneous mixture can be identified using your ……….
A homogeneous mixture needs a ………………… to
distinguish all the components
