Chemical and Physical Properties

Chemical and Physical Properties

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Chemical Properties

What is a chemical property?

Pro tip: Ask yourself...

Flammability

Reactivity

Others...

Chemical and Physical Properties

Chemical Properties

Physical Properties

Physical Properties

Pro tip: Ask yourself...

What is a Physical property?

Viscosity

Luster

Hardness and Brittleness

Conductivity

Malleability

Ductility

Density

Others...

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DENSITY

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What is density (con't)

Working with Density

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Chemical and Physical Changes

Physical Changes

Chemical Changes

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Physical Changes

What is a physical change?

How do you know?

Pro tip!... KNOW THIS!!!

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Chemical Changes

What is a chemical change?

Formation of a Precipitate

Change in color*

Change in temperature*

Production of Gas

A few others...

Production of smoke/fire

Chemical and Physical Properties

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Brittleness:

Hardness:

The tendency of a material to shatter when hit

A material's ability to resist being scratched

Diamonds!

Talc!

If one material is harder than another, it will scratch it!

• Diamonds scratch/cut glass
• Knifes scratch pots and pans

The ability to of a material to be pulled into wires

Ductility:

NOT the same as Malleable!

Somethings can be both, but others that are malleable will fall apart if you try to make it into a wire!

Ask yourself?

• What can I observe with my 5 senses?
• Does it change the original substance?
• Can it be measured without changing the substance

Bubbles or fizzing:

Usually indcates a change in temperature as well.

Examples:

• Baking soda & vinegar volcano
• Alka Seltzer tablet!

Conductivity:

Heat is energy, energy has many forms!!!

The ability of a material to allow heat to flow

• Materials with high conductivity (like metals) are called conductors.
• Good conductors of heat are usually also conductors of electricity.

An UNEXPECTED change in color...

Must be the result of a reaction!

Examples of Chemical changes in color...

• Oxidation: Rusting

• Patina: Copper

• Food Decomposition: An apple browing, etc...
• Leaves changing color... decomposition!
• Dyeing hair: Chemically changing the color of hair

Physical changes in color...

• Painting something:

• Disolving something: like kool-aid powder in water

An UNEXPECTED change in temperature...

Must be the result of a reaction!

Examples of Chemical changes in temperature...

• Burning: Fire, candle wick, etc...
• Fireworks: Combustion!
• Cooking food

Physical changes in temperature...

• Boiling, freezing, melting, etc...

• A heater

A few others...

• Photosynthesis - plants making food!
• Toxicity - if it makes living things sick or is deadly
• Combustion - Spontaneous fire... woot!
• Food cooking, digesting, or decomposing - Can't return it to it's original state! Molecules are forever changed!

Luster: Oooo... shiny!

A measure of how shiny or dull a substance is.

• Oxidation: Rusting

• Patina: Statue of liberty, pennies

• Food Decomposition

Reactivity:

The ability of a material to chemically react with another.

Play ME!

ASK YOURSELF:

• Does it react with something?
• Does it change the original substance?

IF YES... it's chemical!

Density problems are solved using the density triangle!

DO THESE In your notes!

Watch the video if you can't remember how to use the triangle!

What is Density?

The ability of a material to be bent or shaped

Malleability:

Think of a mallet! (although you don't need one)

• Paperclips
• Aluminum foil
• Gold

What is a chemical Change?

Chemical Changes occur when one substance reacts to another and forms ONE or MORE new substances

Can't return it to it's original state! Molecules are forever changed!

Measures a liquids ability to RESIST flowing

Viscosity:

EX: Think of honey and water. Honey has a higher viscosity. It RESISTS flowing more than water because it is so thick.

Karo Syrup... thick liquid!

Water... thin liquid!

• Thick liquid = HIGH viscocity, moves SLOW
• Thin liquid = LOW viscocity, moves FAST
• Viscosity increases as temperature decreases...

(an inverse relationship! )

HIGH temp! LOW temp!

Phase changes are reversible! So...

Key to problems on notes...

Complete this...

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Ask yourself...

Is it the same substance? If yes... physical change If no... NOT physical change, but chemical!

1. If chocolate melts, is it still chocolate? YES (just a bit messy!)... physical! 2. If a pencil is snapped in half, is it still a pencil? YES... physical! 3. If a pencil is burned, is it still a pencil? NO... chemical! 4. If I bake a cake is it still a cake? NO... ALL cooking/baking is chemical!

Smoke or Fire:

There are a few more chemcial properties

Here are a few more worth noting:

• Toxicity- the ablity for a substance to be harmful to living things or the environment EX: mercury, lead
• Corrosivity - the ability to make something corode (break down) by coming into contact with it EX: sulfuric acid
• pH - the ability to produce hydronium!
• Neutralization - the ability to counteract an acid or a base

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Density

Density...

is the ratio of an object's mass compared to its volume.

Less dense More dense Donuts Bagels

• Things that are more dense have more mass in the same amount of space/volume
• In liquids, objects with higher density than water (1g/ml) will sink and lower density will float.
• The formula for density is d=m/v Unit is g/(cm^3 ) or g/ml

Solids or liquids!

A precipitate:

A Solid that forms and separates (falls out) from TWO liquids combining during a chemical change.

It is NOT rain!

Real Life Example! Cottage Cheese: Liquid milk is combined with liquid acetic acid forming the solid "curds" in cottage cheese!

Flammability

The ability of a material to burn in the presence of oxygen.

Examples:

• Gasoline
• Natural Gas
• Children's clothing*

In 1953 a law was passed requiring children's pajamas and mattresses be treated with flame retardant before going to market so they would be less flammable.

What is a Physical Property?

A Physical Property is any characteristic of material that can be observed or measured WITHOUT changing its composition. They describe the appearance or behavior of a substance

• Shape, size, texture, etc...
• State of matter
• Mass, volume, temp, etc...

What is a chemical Property?

Formation of a Precipitate

A Chemical Property is a characteristic of material that has the ability to change the composition of matter. It happens when the original substance is changed into a different substance.

What is a Physical Change?

A Physical Change results from a change in one or more property, but not a change in substance.

• Can be a change in size, shape, texture, form, etc...
• Usually, reversible, meaning it can return it to it's original state!

--> Molecules are NOT changed!

• Examples:
• Painting a fence, cutting hair, sharpening a pencil, etc...

There are tons of physical properties

Here are a few more worth noting:

• Solubility - the ablity for a substance to dissolve in another
• Odor, color, texture, shape, temperature
• Melting, boiling points