P. Sci. Unit 7 Chapter 2 Matter
Jan 18, 2016
P. Sci.
Unit 7
Chapter 2
Matter
Chemistry
• What things are made of and how things change.
Matter
• Has mass and takes up space.
• Matter is made up of atoms
• Light sound and electricity are NOT matter
AtomsThe smallest particle that
has the properties of
an element.
Element – a substance that cannot be broken down into simpler substances.
All the atoms in the substance are alike
Elements• Each element has a one or two
letter symbol used worldwide to designate it.
• The chart that shows
all the known elements
is called the Periodic
Table of Elements.
Compounds
• When two or more elements combine chemically you get a compound.
Molecule• The smallest unit of a substance
that exhibits all the properties of that compound.
Chemical formulas• The combination of chemical
symbols (and how many atoms of each) make up a molecule of a substance.
Pure vs. Mixtures
• Pure substances – any substance that has a fixed composition and definite properties.
Table sugar – C12H22O11
• Mixtures - A combination of substances that are not fixed;
they can change
OJ – is a mixture of water, citric acid and sugar among other things. Any drop of Orange Juice can have different amounts of the different components.
Classifications of Mixtures• Homogeneous Mixtures – a
mixture that is the same throughout (completely mixed)
• Heterogeneous Mixtures – a mixture where you can see all the parts. (incompletely mixed)
Properties of Matter
• Physical Properties
• Chemical Properties
• Physical Changes
• Chemical Changes
Changes of Matter
Physical Properties• characteristics of a material which
can be observed without changing the identity of the substances in the material.
• examples include color,
shape, size, melting point, and boiling point.
• Appearance – physical description of a substance.
• Behavior – how a substance acts; for example, magnetism, viscosity, ductility.
• Physical properties such as size and magnetism can be used to separate mixtures.
Chemical Properties• Characteristics of a substance
indicating that it can change chemically.
• Examples: flammability or light sensitivity of a substance, production of a gas, production of a precipitate, change in odor.
Physical Change• A change in a substance’s
physical property (properties).
• Substance does not change identity when it undergoes a physical change.
• Examples: change in size, shape, or state of matter
Chemical Change• When one substance
changes to another substance.
• Some chemical changes are indicated by temperature change, smell, or bubble formation.
• Other chemical changes occur very slowly such as the formation of rust.
Density• The mass per unit volume of
a substance.
(how much matter is packed into a specific amount of a substance)
• d = m/v
• Density is a physical property.
Dissolving• When a substance dissolves, it
seems to disappear because the particles of the substance spread out between the particles of the liquid. Neither substance changes into another substance, therefore:
• Dissolving is a physical change.
Change of State• When a substance goes from one
state of matter to another the substance does not change into another substance. (ice, water, steam – are all H2O)
Therefore – Change of State is a Physical Change.