Physical versus Chemical Properties & Changes

Chapter 1 – Section 3Changes in Matter

• Matter: anything that has mass and takes up space– Mass – the amount of matter in something– Volume – the amount of space something

occupies

• Which of the following is matter?– A car?– A box?– You?

Reviewing MATTER

What is a property?

• CHARACTERISTIC PROPERTY: A characteristic of a substance that can be observed and/or measured

What are characteristic properties good for?

• We can use these properties to identify substances.

• 2 basic types of properties of matter:

PHYSICAL and CHEMICAL• ALWAYS the same whether object is large

or small

Physical Property

PHYSICAL PROPERTY: A property that can be observed WITHOUT CHANGING the identity of the substance.

A feature of a substance that does NOT involve a chemical change.

Same substance, same compounds you started with.

Physical Property

Examples:

* Color * Shape * Hardness* Density* Texture

* State @ room temp (solid, liquid, gas) * Size (mass, volume)

* Melting point* Boiling point

* Malleability (hammer into sheets)* Ductility (stretch into wires)* Taste (don’t taste unknown chemicals!)* Odor (don’t sniff unknown chemicals!)* Luster (surface appearance)– shiny, dull* Solubility (ability to dissolve in a substance)* Electrical conductivity * Thermal conductivity (heat)* Sound conductivity

Chemical Property

CHEMICAL PROPERTY:

•A property that can only be observed by CHANGING the identity of the substance.

•Characteristics that indicate if a material can undergo a certain chemical change.

•A property of matter that describes its ability to be involved in chemical reactions.

•Chemical properties can ONLY be observed AS the substances are changing into different substances.

Chemical Property

Examples:

* Flammability (Combustibility)– ability to burn

* Ability to rust from oxygen

* Reactivity with water or vinegar

* Toxicity- how dangerous the material is

* Radioactivity- does the material give off radiation

* Sensitivity to light- how sensitive the material is when placed under a light or the sun

Physical changes are those changes that DO NOT result in the production of a new substance.If you melt a block of ice (frozen H2O), you still have H2O at the end of the change.   

Physical Changes

If you break a bottle, you still have glass.  Painting your nails will not stop them from being fingernails.  Some common examples of physical changes are: melting, freezing, condensing, breaking, crushing, cutting, and bending.

Physical Changes

Affects one or more physical properties of a substance, but not chemical properties or identity of a substance (appearance affected, but not composition)

Physical Changes

Some, but not all physical changes can be reversed. You could refreeze the water into ice, but you cannot put your hair back together if you don’t like your haircut!

Physical Changes

Chemical Changes

•Chemical changes, or chemical reactions, are changes that result in the production of another substance.

•Occurs when 1 or more substances change into entirely new substances with different characteristic properties.

•Cannot reverse chemical changes using physical means, sometimes cannot reverse at all

Common examples of chemical changes that you may be somewhat familiar with are: digestion, respiration, photosynthesis, burning, and decomposition. 

Chemical Changes

FLAMMABILITY: A material’s ability to BURN in the presence of OXYGEN

Chemical Changes

When you burn a log in a fireplace, you are carrying out a chemical reaction that releases carbon.  When you light a candle at home, you are carrying out a chemical reaction that produces carbon (soot) and carbon dioxide gas. 

Chemical Changes

REACTIVITY:How readily (easily) a substance combines chemically with other substances.

Chemical Changes

Clues to Chemical Changes

Dramatic color change (can’t use this alone!)

Fizzing, foaming (new production of gas)

Precipitate (new production of solid

substance)

Production or use of energy (light, heat)

Production of sound, odor

QUIZ TIME

Physical or Chemical Change?

•Painting Wood•PHYSICAL

Physical or Chemical Change?

Physical or Chemical Change?

•Digestion of food•CHEMICAL

Physical or Chemical Change?

•Sugar dissolving in water

•PHYSICAL

Physical or Chemical Change?

•Iron turning red when heated•PHYSICAL

Physical or Chemical Change?

•Evaporation•PHYSICAL

Physical or Chemical Change?

•A pond freezing in winter

•PHYSICAL

Physical or Chemical Change?

•Melting ice•PHYSICAL

Physical or Chemical Change?

•Cutting wire•PHYSICAL

Physical or Chemical Change?

•Painting fingernails•PHYSICAL

Physical or Chemical Change?

•Cutting fabric•PHYSICAL

Physical or Chemical Change?

•Baking muffins•CHEMICAL

Physical or Chemical Change?

•Shattering glass•PHYSICAL

Physical or Chemical Change?

•Decomposition of old leaves

•CHEMICAL

Physical or Chemical Change?

•Wrinkling a shirt•PHYSICAL

Physical or Chemical Change?

•An old nail rusting•CHEMICAL

Physical or Chemical Change?

•Burning Paper•CHEMICAL