1. Physical and Chemical Properties 2
Lesson 4
September 27th, 2010

2. Temperature and Chemical Change
The application of heat to a substance can cause chemical changes.
If enough heat is applied to a combustible material it will burst into flames.

3. Temperature and Chemical Change
Combustibility – The ability of a substance to react quickly with oxygen to produce light and heat.
A reaction that gives off heat is known as an exothermic reaction.
Example: burning gasoline.

4. Temperature and Chemical Change
When some substances are mixed and their reaction absorbs heat, it is called an endothermic reaction.
Example: A chemical cold pack.

5. Controlling Changes in Matter to Meet Human Needs

6. Freezedrying
A method of food preservation. (can last from months to years)
Food is frozen and then placed in a pressure chamber where the pressure is reduced until the solid water sublimes into gas.

7. Freezedrying To cook just add hot water
98% of the water is removed and once packaged does not need to be refrigerated.
To cook just add hot water

8. From Corn to Biodegradable Plastic Wrap
Chemicals made from corn can be used to make juice bottles, remove paint or nail polish, and fuel some cars.

9. From Corn to Biodegradable Plastic Wrap
Corn is put through a chemical change called fermentation. Once this chemical process is complete, the new substances are recovered, purified, and made into solvents, biodegradable plastics, and automobile fuel.
Solvents are substances that dissolve other substances.
Corn-based solvents are not as harmful to the environment as some other types of solvents.

10. From Corn to Biodegradable Plastic Wrap
An advantage of corn-based biodegradable plastics is that they can be broken down by bacteria.
Corn-based products also have their drawbacks.
Rainforests have been cut to make corn fields.
Corn that would otherwise be used for food is sometimes diverted to make disposable products

11. Things to hand in Investigating Physical and Chemical Changes
You will write a quiz
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