Physical Property :Characteristic of a material that can be observed or measured without changing the composition of the substances in the material.– Examples:

– Viscosity – conductivity – malleability – hardness – melting point – boiling point– density

Physical Properties

Viscosity –Tendency of a liquid to keep from flowing

• Thick liquids high viscosity.

• Thin liquids low viscosity.

Examples of Physical Properties

Conductivity -Ability to allow heat or electricity to flow

• Materials that have a high conductivity, such as metals, are called conductors.

• Good conductors of heat are usually also good conductors of electricity.

Examples of Physical Properties

Malleability -The ability of a solid to be hammered without shattering

• Most metals, such as gold, are malleable. Solids that shatter when struck are brittle, not malleable.

• An ice cube or piece of glass breaks into small pieces when struck with a hammer.

Examples of Physical Properties

Hardness - resistance to scratchingOne material can scratch another material if it is harder than the other material.

Examples:•A kitchen knife can scratch a copper sheet because stainless steel is harder than copper.•The material used to sharpen the knife blade must be harder than stainless steel.•Diamond is the hardest known material.

Examples of Physical Properties

Melting and Boiling Points -Temperature at which material changes state

• Melting point (freezing is same temperature) Melting solid to liquid Freezing liquid to solid

• Boiling point (condensing is same temperature) Boiling liquid to gas Condensing gas to liquid

Examples of Physical Properties

Density – the ratio of the mass of a substance

to its volume (i.e. mass/volume)• Characteristic Property• Density can be used to test the purity of a

substance. • Silver has a density of 10.5 g/cm3. A coin

with a density of 9.9 g/cm3 is not made from silver, or it contains substances in addition to silver.

Examples of Physical Properties

Physical properties are used to:

•Identify materials•Choose materials for a specific purpose

•Separate the substances in mixtures.

Examples of Physical Properties

Distillation – separates the substances in a solution based on their boiling points.Examples: gasoline, moonshine

Using Properties to Separate Mixtures

• Filtration and distillation are two common separation methods.

Physical change: Substances in the material remain the same.Some of the properties of a material change, properties such as: Size, Shape, State of matter (solid, liquid, or gas) Examples include:

Water going from a liquid to a gas during boilingMelting butter in a panCrumpling a piece of paperSlicing a tomato

Recognizing Physical Changes

Some but not all physical changes can be reversed.

Braiding hair is a reversible change. Cutting hair cannot be reversed. Both are physical changes.

As a candle burns, its compounds combine with oxygen in the air to form water and carbon dioxide.

Chemical property – ability to produce a change in the composition of matter.

Examples: Flammability Reactivity

Chemical Properties

Flammability A material’s ability to burn in the

presence of oxygen. Materials that burn can be used as fuel.

Reactivity How readily a substance combines

chemically with other substances

Chemical Properties

Rust forms when oxygen reacts with iron and water. Rust is a brittle, reddish-brown compound. Because iron is highly reactive, you would not choose iron to make jewelry or coins.

Chemical Change

A chemical change occurs when a substance reacts and forms one or more new substances. Example:

The color change in a banana peel is caused by chemical changes that are taking place in the cells of the banana.

Recognizing Chemical Change

3 common types of evidence for a chemical change:

•Change in color•Production of a gas•Formation of a precipitate.

Recognizing Chemical Change

Change in Color – a clue that a chemical change may have produced at least one new substance.

Examples:•A shiny silver bracelet that is exposed to air will darken. •As a match burns, it shrivels up and turns black. •A new copper roof and an old copper roof have different colors.

Recognizing Chemical Change

A new copper roof has a reddish color.

The green patina on an old copper roof is a mixture of copper compounds.

Recognizing Chemical Change

Production of a GasVinegar + Baking Soda bubbles of carbon dioxide form immediately.

A similar chemical change happens when you use baking powder as an ingredient in a cake recipe. Bubbles of carbon dioxide expand and cause the cake to rise.

Recognizing Chemical Change

Formation of a PrecipitatePrecipitate – any solid that forms and separates from a liquid mixture. Example:

When an acid is added to milk, proteins in the milk undergo a chemical change that causes them to stick together in clumps and form a precipitate cottage cheese.

Recognizing Chemical Change

Color change, a gas, or a precipitate DO NOT guarantee that a chemical change has taken place. When an iron horseshoe is heated, its

color changes from gray to red, but the iron is still iron. That means the change is physical, not chemical.

Chemical Changes

Chemical change: composition of the matter changes.

You got something NEW

Physical change: composition of the matter stays same.

• Are different substances present after a change takes place? If not, then the change is physical, not chemical.

Chemical Changes