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.