DESCRIBING MATTER

Anything that has mass and takes up space

Substance - single kind of matter that has a specific

make-up and specific properties Example: Salt or sugar

Non-Example: Muffin batter (the ingredients can vary)

MATTER

Can be observed without changing into another substance

Examples: Freezing point, melting point, density, texture, color, flexibility, solubility in

water

PHYSICAL PROPERTIES OF MATTER

Ability to change into a different substance

Examples: flammability, rusting, tarnishing, rising of bread in baking process

CHEMICAL PROPERTIES OF MATTER

Pure substances that cannot be broken down into any other substance

Simplest substances - identified by its specific

physical and chemical properties

Examples: Carbon, Oxygen, Gold, Silver, Aluminum

ELEMENTS

Basic particle that makes up all elements

Having different atoms gives elements their unique properties

Atoms have parts! The nucleus is made up of positively charged

protons and neutrally charged neutrons.The nucleus is surrounded by a cloud of

negatively charged electrons.

ATOMS

Pencil “lead” is made of mostly graphite, a form of

carbon.

Two ways to model atoms used in this presentation

are shown here for carbon.

MODELING AN ATOM

Atoms combine by chemical bonds (a force of attraction between the electrons of 2 or

more atoms).

Often form molecules- groups of 2 or more atoms held together by chemical bonds

Examples: H2O, O2, CO2

CHEMICAL BONDS

MODELING MOLECULES

How many atoms are in each of these molecules?

Pure substance made up of 2 or more elements chemically combined in a set ratio

Represented by a chemical formula which shows the elements in the compound and the ratio of atoms

When elements combine to form compounds, they have unique properties from those of the uncombined elements

-Example: Hydrogen alone is a very combustible gas, Oxygen alone is a major supporter of combustibility, but when

combined in the set 2:1 ratio H2O, they put out fires!

COMPOUNDS

A ratio compares two numbers. It tells you how much you have of one item compared to how much you have of

another. For example, a cookie recipe calls for 2 cups of flour to every 1 cup of sugar. You can write the ratio of

flour to sugar as 2 to 1, or 2:1.

The chemical formula for rust, a compound made from the elements iron (Fe) and oxygen (O), may be written as

Fe2O3. In this compound, the ratio of iron atoms to oxygen atoms is 2:3. This compound is different from FeO, a compound in which the ratio of iron atoms to oxygen

atoms is 1:1.

RATIOS

Practice Problem

What is the ratio of nitrogen atoms (N) to oxygen atoms (O) in a compound with the formula N2O5?

Is it the same as the compound NO2? Explain.

N2O5 contains two nitrogen atoms for every five oxygen atoms. Both N2O5 and NO2 are made up of only nitrogen atoms and oxygen atoms. However,

the two compounds are different because NO2 contains one nitrogen atom for every two oxygen

atoms.

RATIOS

Made up of 2 or more substances that are not chemically combined

Differ from compounds because they do not have to have a set ratio, and each substance

in mixture keeps its individual propertiesExamples: Air, Soil, Salt water

MIXTURES

Hetero = differentCan see different parts of mixture

Examples: Soil, Salad

HETEROGENEOUS MIXTURES

Who can think of other examples?

Homo = sameCan’t see different parts of mixture,

evenly mixedExamples: Sugar/water solution, Air

HOMOGENEOUS MIXTURES

Who can think of other examples?

Compounds are hard to separate

Mixtures are easy to separate since each component keeps its own properties

Look at figure 10 on page 66, it shows different ways to separate a mixture including using a magnet, filtering,

distilling, and evaporating

SEPARATING MIXTURES

LET’S REVIEW!!

What are some examples of chemical properties of matter?

Rusting, flammability, bread

baking

What are some examples of physical properties of matter?

Density, melting, freezing, color,

flexibility, hardness

LET’S REVIEW!!

What 2 things does a chemical formula

show?The elements

present and the ratio of atoms

Give an example of an element.

Carbon, Oxygen, Nitrogen, Gold,

Silver, etc.