Section 2-1

 L State how matter and changes in matter can be described.  L Explain how you can tell when a chemical change has occurred.

 Matter can be described in terms of two kinds of properties-physical properties and chemical properties.  Changes in matter can be described as physical changes and chemical changes.  Objective L

 A physical property is a characteristic that can be observed of a substance that does not require changing that substance into something else. Can you think of some physical properties of the forest?

 Can you think of some physical properties of the crystal?  Color  Mass  Density  Cleavage/Fracture  Smell  NEVER TASTE SOMETHING IF YOU DON’T KNOW WHAT IT IS!!!

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 A chemical property is a property of a substance that allows it to change into another substance. What are a couple of examples of a chemical property.  Ability to Burn.  Rusting

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PHYSICAL  A physical change is a change in the appearance, form, texture or state of matter but the matter DOES NOT become a new substance. CHEMICAL  A chemical change is a change in the matter that DOES turn it into a new and, sometimes, a very different substance.

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 What are the four states of matter?  Solid  Liquid  Gas  Plasma  Don’t worry about plasma right now, we will come back to it in Astronomy.

 When matter changes state from solid to liquid to gas or gas to liquid to solid, it is always a physical change. Why?  Because the substance has not changed into a different substance.

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 What do we see in this picture?  Steam  Water  Ice  Has the substance changed into something new?  No, it has only changed state.

 The water molecules in ice are crystalline in structure and ice is a solid but look at the molecules. What are they made of?  H2O

 The molecules in liquid water are no longer crystalline and they are now able to move around but look at the molecules again. What are they made of?  H2O

 The molecules of water are now very excited and far apart. This is steam but look at the molecules one more time. What are they made of?  H2O

 In any of these cases, did the actual chemical composition change?  No, it was always 2 hydrogen’s and one oxygen.

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 Chemical changes occur when old chemical bonds are broken, new chemical bonds form or both creating new, and often, different substances. Objective L

 Changes reactions involve two main types changes that you can observe. Changes in the substances and changes in energy. Objective L

 Sometimes when you can see unexpected changes in substances it is an indication that a chemical change has occurred. Those indications are:  A gas is produced  A solid is produced  An unexpected color change has occurred.

 One that we can’t see is the production of water. We will come back to this one in Section 2-2.

 Another way to determine is a chemical change has occurred is a change in energy, usually heat but sometimes light. There are two types of heat reactions.  Endothermic  Exothermic

 What does endo mean?  It means into, like enter.  What does thermic mean?  It means heat.  So endothermic means  It means heat moves into something or that something is absorbing heat. So the substance will feel?  Cold

 What does exo mean?  It means out of, like exit.  What does thermic mean?  It means heat.  So exothermic means,  It means het moves out of something or that something is releasing heat. So the substance will feel?  Hot

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