Physical and Chemical Changes

Matter  Matter is everywhere.  Matter is anything that takes up space and has mass.  Matter is constantly experiencing both chemical and physical changes.

Introduction  There are two types of properties of matter, they are physical properties and chemical properties.  There are also two types of changes in matter they are physical changes and chemical changes.  Let’s talk about physical properties first.

Physical Properties  A physical property is any characteristic of a material that one can observe easily without changing the substances that make up the material.  Every substance has physical properties that distinguish it from other substances.

Physical Properties  Physical property examples…  shape  Size  Color  Smell  Temperature  Volume  Density  melting point  boiling point  state of matter.

Physical Changes  A change in physical properties is called a physical change.  Physical changes do not alter the identity of a substance.  Pounding, pulling, cutting, dissolving, melting, or boiling do not produce a new substance with new properties, so they are all physical changes.

Physical Change

Physical Change Example  For example if you take a piece of paper and tear it into pieces you still have paper. It may be smaller, but it’s still paper.  You could dye the paper and make it another color, but it’s still paper.  You have only changed it physically.

Physical Changes of Water Freezing-liquid to a solid; this change requires cooling Melting-solid to a liquid: this change is speeded up by heating. Condensation-gases change to a liquid; this change requires cooling. Vaporization/Evaporation-liquid changes to gas; this change is speeded up by heating. Sublimation- a solid changes to a gas without passing through the liquid state (e.g., dry ice, solid to gas)

What Do You Think?  Can you name this physical change of water?  Here’s a hint: The water is changing from the gas to the liquid phase.

What Do You Think?  Can you name this physical change of water?  Here’s a hint: The water is changing from the liquid to the gas phase.

Chemical Change  Chemical changes are changes matter undergoes when it becomes new or different matter.  To identify a chemical change look for signs such as color change, bubbling and fizzing, light production, smoke, and presence of heat.

Chemical Properties/Changes  Substances can change their identities, for example, fireworks explode,

Chemical Properties/Changes  matches burn

Chemical Properties/Changes  Food cooks

Chemical Properties/Changes  And iron rusts

Chemical Properties/Changes  Burned toast, burned soup, and burned steak all smell burned. The smell is different from the smell of bread, soup, or steak.  The odor is a clue that a new substance has been produced.

Chemical Change  A change of one substance in a material to a different substance is a chemical change.  In some chemical changes a rapid production of energy, such as the production of heat, light, sound or gas bubbles occur. These things indicate that a chemical change has occurred.  Burning and rusting are chemical changes because different substances are produced.

Chemical Change  A baked cake no longer resembles its ingredients of flour, eggs, butter, and sugar, because the reactants have undergone a chemical change.  A chemical reaction is simply breaking substances (reactants) apart and making new ones (products) from the pieces. reactants product

Chemical Reactions  Those ingredients have been changed by a chemical reaction.  A chemical reaction is simply breaking substances (reactants) apart and making new substances (products) from the pieces.

Chemical Reactions  Whenever a chemical reaction takes place, new substances, the products, are made.  These have very different properties from the original starting materials, the reactants. reactant + reactant = product

Now let us try some examples

In which situation is a chemical reaction occurring? a.salt dissolving in water b.a nail rusting c.ice melting d.a glass window breaking

In which situation is a chemical reaction occurring? a.salt dissolving in water b.a nail rusting c.ice melting d.a glass window breaking

Which of the following is a chemical change? a.dissolving sugar in iced tea b.bending copper wire c.a cavity in a tooth d. drops of water forming on the outside of a cold glass

Which of the following is a chemical change? a.dissolving sugar in iced tea b.bending copper wire c.a cavity in a tooth d. drops of water forming on the outside of a cold glass

All of the following are physical changes except – a.melting ice cream. b.distillation of sea water. c.rusting of an iron nail. d.folding a piece of paper.

All of the following are physical changes except – a.melting ice cream. b.distillation of sea water. c.rusting of an iron nail. d.folding a piece of paper.

Which of these warnings or recommendations refers to a chemical property? a.shake well b.fragile – glass c.flammable d.caution – sharp edges

Which of these warnings or recommendations refers to a chemical property? a.shake well b.fragile – glass c.flammable d.caution – sharp edges

Which of the following is a chemical change? a.boiling b.burning c.freezing d.evaporation

Which of the following is a chemical change? a.boiling b.burning c.freezing d.evaporation

Is it a chemical or physical change?  Sugar dissolving in tea Chemical Change Physical Change

OOPS! Did it change size, color, shape (Physical Change)? or Did it become different matter (Chemical Change)?

Correct!

Is it a chemical or physical change?  Logs burning Chemical Change Physical Change

OOPS! Did it change size, color, shape (Physical Change)? or Did it become different matter (Chemical Change)?

Correct!

Is it a chemical or physical change?  Breaking water up by separating it into hydrogen and oxygen Chemical Change Physical Change

OOPS! Did it change size, color, shape (Physical Change)? or Did it become different matter (Chemical Change)?

Correct!

Is it a chemical or physical change?  Cutting paper Chemical Change Physical Change

OOPS! Did it change size, color, shape (Physical Change)? or Did it become different matter (Chemical Change)?

Correct!

Is it a chemical or physical change?  Crushing an aspirin Chemical Change Physical Change

OOPS! Did it change size, color, shape (Physical Change)? or Did it become different matter (Chemical Change)?

Correct!

Is it a chemical or physical change?  Metal rusting Chemical Change Physical Change

OOPS! Did it change size, color, shape (Physical Change)? or Did it become different matter (Chemical Change)?

Correct!

Is it a chemical or physical change?  Lighter fluid burining Chemical Change Physical Change

OOPS! Did it change size, color, shape (Physical Change)? or Did it become different matter (Chemical Change)?

Correct!

Is it a chemical or physical change?  An egg rotting Chemical Change Physical Change

OOPS! Did it change size, color, shape (Physical Change)? or Did it become different matter (Chemical Change)?

Correct!

Is it a chemical or physical change?  An egg breaking Chemical Change Physical Change

OOPS! Did it change size, color, shape (Physical Change)? or Did it become different matter (Chemical Change)?

Correct!

Writing Activity  Write a paragraph about the difference between a chemical and physical change. Give examples of each.