4. Physical vs Chemical Change
• Physical changes- form or appearance changes but
composition stays the same- (Example- phase changes:
evaporation, condensation, freezing)
• Chemical changes- change the chemical composition of the
substance- chemical bonds are broken and reformed.
Burning changes wood to ash, smoke, gases
• Chemical changes happen at the molecular level, result in
new products, and are not easily reversed.
5. Physical vs Chemical Change
• Changes in matter are constantly occurring around us.
• These changes are either physical or chemical
• Eating is a great example of both! It involves both physical
(chewing with teeth, mixing with tongue) and chemical
(breakdown by saliva, digestion by stomach acids) changes.
15. Today’s Warmup
• What does that word mean- “organic”???
• What does that word mean- “compound”???
• In you lab-book write a definition in your own
words. Don’t worry if it turns out to be incorrect or
only partially correct, just write what you think.
16. Organic compounds always have carbon joined
to itself or hydrogen, and other elements like
oxygen, and nitrogen, phosphorus, or sulfur.
17. There are organic compounds that make
up you!- your hair, your skin, even your
fingernails… And carbon is a part of all of
18. So, why is carbon such a special element?
Watch a video!
21. Why is carbon such a special
• Each carbon atom can form strong, stable bonds with four
other atoms at a time – these are usually oxygen,
hydrogen, nitrogen, sulfur, and phosphorus atoms.
• Carbon can also bond to other carbon atoms to form chains
that are almost unlimited in length.
• This creates a huge number and variety
of molecules that can be built from
carbon atoms. No other element even
26. Organic Building Blocks
•The name, carbohydrates, is a good
one because it indicates carbon and
water (hydrogen and oxygen).
•Remember, dehydrated means loss of
water, and to be hydrated means to add
27. Saltine Mini-Lab
EXPLORE – Digestion Changes
1. Have students place a soda cracker on a paper towel and crush the
cracker with their hand.
How did the cracker change?
Was this change a physical or chemical change for the cracker?
2. Have students take the second cracker and chew it for about a
minute. Caution students not to swallow the cracker.
What was the first taste you noticed in your mouth?
What was the second taste you notice?
28. Saltine Mini-Lab
EXPLORE – Digestion Changes
Students may have to hold the cracker in their mouth for 2 min to allow
time for the carbohydrates to break down into sugar. Encourage them
to fight the urge to swallow.
Do you think this change in taste indicates a physical or chemical
Soda crackers are high in carbohydrates in the form of starch.
An enzyme in saliva begins breaking down the starch into
sugar. That is why the cracker tasted sweet. Two forms of
digestion occur in the mouth. Physical digestion began when
you chewed the cracker. Chemical digestion occurred when the
saliva started breaking down the starches.
29. Organic Building Blocks
•Lipids (oils and fats) are
another class of organic
compounds built from oxygen,
hydrogen, and carbon. It's
amazing what these three
elements can build!
31. Organic Building Blocks
A few amino acids are built by carbon, hydrogen, oxygen, nitrogen,
Mammals need about 20 amino acids to make the proteins they need.
Only 2 of these are amino acids containing sulfur.
32. Organic Building Blocks
We will end our organic building blocks with the ultimate building block
of living organisms- DNA.
We need just one more element to build it: phosphorus.
33. Organic Building Blocks Review
• Hydrocarbons= hydrogen + carbon
• Carbohydrates and Lipids = hydrogen, carbon, and oxygen
• Amino Acids and Proteins = hydrogen, carbon, oxygen, and
• Some Amino Acids and Proteins = hydrogen, carbon, oxygen,
nitrogen, and sulfur
• Nucleic Acids = hydrogen, carbon, oxygen, nitrogen, sulfur,
34. One more question…
• Where do these elements that make up our
bodies come from? I mean, where did the
come from originally???
• They came from exploding stars!
– But that’s a lesson for another day…