Warm Up: Process your notes from last class!! (physical and chemical properties)

Remember: *Add questions/key words in the left column or margin

*1-2 sentence summary at the bottom of the page (if you didn’t leave room for this, do it on the bottom of the back of the page)

Physical & Chemical Changes

Physical Changes • Only alter the form or appearance of matter

• A substance that undergoes a physical change is still the same substance after the change

How can you tell?

There are some indicators that will let you know when a physical change has taken place:

– Phase change – You just physically mixed things together (like Kool-Aid

or a salad) – The only thing that changes is the shape or size

– There is an expected color change – A lot of times the change can be reversed

Physical Changes A physical change is similar to changing the font

of a word… Basketball

Basketball Basketball

Basketball Basketball

Basketball

Basketball Basketball Basketball

The structure of the word is still the same, but the physical appearance has changed.

Quick Check 1) You are given a piece of paper. What are 2

things that you could do to the paper that would result in a physical change?

2) When something changes state, like melting

ice for example, why is it considered a physical change?

Chemical Changes • Produce one or more new substances

How can you tell?

There are some indicators that will let you know when a chemical change has taken place: – Anytime something is cooked and/or burned

– Light, sound, and/or heat is produced – A gas is produced (or you see fizzing or bubbling)

– A precipitate forms – There is an unexpected color change

What is a precipitate?

A precipitate is a solid that forms from the reaction of 2 liquids.

As you watch the following video…

Look for any indications that a chemical change is taking place.

https://www.youtube.com/watch?v=hKoB0M

HVBvM

Chemical Changes • A chemical change is like rearranging the

letters of a word… Basketball

Let Blab Ask Lab Bat Elks Ask Bell Tab Stab Elk Lab Bask At Bell

The structure has been rearranged and new words were made.

Chemical Changes • Chemical changes can be endothermic (absorb energy) or

they can be exothermic (release energy).

• The prefix “endo” means enter. An example of an endothermic reaction is an ice pack.

• The prefix “exo” means exit. An example of an exothermic reaction is an explosion.

Quick Check 1) On a hot summer day, you & your best

friend decide to make Kool-Aid. Your best friend thinks that dissolving the sugar and

Kool-Aid packet into the water makes a new substance & it is a chemical change. Do you

agree or disagree? Explain.

Physical or Chemical Change? Complete the “explain” column of your chart!

You must say either physical or chemical AND

explain WHY!

True or False?

1) In an endothermic reaction, energy is absorbed.

2) A precipitate is an indication that a physical change has taken place.

3) Melting butter is an example of a physical change.

4) A chemical change is similar to changing the font of a word.

5) A chemical change can usually be reversed.

Determine whether the following statements are true or false. If the statement is false, what could we change the underlined word to in order to make the statement true?