physical and chemical changes. physical and chemical properties everything around us has physical...
TRANSCRIPT
Physical and Chemical Changes
Physical and Chemical Properties
Everything around us has physical and chemical properties.
Physical Properties
• Characteristics you can observe without changing the substance into something new.– Use your senses to describe– state of matter– measurement
• Use your senses… How does it look, smell, sound, feel, taste (don’t taste it unless the teacher says it’s ok)
• What state of matter is it? (solid, liquid, or gas)
• Measure it….mass, weight, volume, length, width, height, density, temperature, magnetic?
Physical Properties
• List as many physical properties as you can
Color
Temperature
Feel
Smell
State
Weight
Length
Density
Chemical Properties
• Will it burn, explode, react with other elements?
• Characteristics that you can only observe by changing the substance into something new.– You can’t always tell chemical properties just by
looking
Chemical Properties
• List as many chemical properties as you can
Will it burn
Will it explode
Can it react with other things
Physical and Chemical Changes
Matter around us can undergo changes.
Physical Changes
Chemical Changes
Physical Change
• A change in which the form or appearance of matter changes but not its composition– Change of state– Change of shape– Dissolving
Physical Changeschanging state
melting – solid to liquid condensation – gas to liquid
freezing – liquid to solid sublimation – solid to gas
vaporization – liquid to gas deposition – gas to solid
Changes in States
Physical Changeschange of shape
Matter can change shape
cutting
tearing
grinding
crumpling
bending
Physical Changesdissolving
When you mix or dissolve one thing into another, it is a physical change
Chemical Change
• A change in which the composition of matter changes and new substances are formed– It cannot easily be turned back into the original
substance
Chemical Change
• Signs that a chemical change may have taken place– Color change– Absorption or release of energy– Odor– Formation of gases or solids– Can’t be reversed
Signs of chemical changes• The best sign of a chemical change is that at
the end-you have a new substance!• Other common signs:
Color changeColor change
More signs of a chemical changeTakes energy or releases energy (cooking,
burning, produced light, electricity, fireworks)Before- mixing all of the ingredients, I could get all of the pieces back, so stirring together is a physical change
Before- mixing all of the ingredients, I could get all of the pieces back, so stirring together is a physical change
After I put the batter in the oven, the energy changes the make-up of the matter, I can not get batter back!
After I put the batter in the oven, the energy changes the make-up of the matter, I can not get batter back!
Releasing energy
Before: nothing in the sky (this was difficult to make. Before: nothing in the sky (this was difficult to make.
And after- fireworks!!!! Release energy as heat and light
And after- fireworks!!!! Release energy as heat and light
More signs of a Chemical Change
Change in smell or odor
Yummy milk- fresh from the cow (or super market)Yummy milk- fresh from the cow (or super market)
Rotten milk- I hope you never smell this!Rotten milk- I hope you never smell this!
Last sign of a chemical change• Making a gas or a solid without the use
of energy
Ammonium carbonate precipitates white SrCO3. Sr2+
(aq) + CO32-(aq) <==> SrCO3(s)
Ammonium carbonate precipitates white SrCO3. Sr2+
(aq) + CO32-(aq) <==> SrCO3(s)
Reversible
Q:What does it mean for a change to be reversible?
A:It can be put back - From Mirriam-Webster dictionary: capable of
going through a series of actions (as changes) either backward or forward <a reversible chemical reaction>
Is the change reversible?
• Folding paper?• Tearing your shirt? • Cutting your hair?• Eating an apple? • Burning some wood? • Cooking chicken?
Chemical ChangesIron + oxygen and water = rust
silver + oxygen and water = tarnish
Chemical Changes
Burned wood
Cooked food
Chemical ChangesLeaves turning in fall
Spoiled food
Chemical ChangesLightning bug
Antacid tablet
Physical or Chemical
Copper jewelry
Statue of Liberty
orange Orange juice Orange cake
copper
Physical Chemical
Physical Chemical
Law of Conservation of MassThe total mass of matter before and after
a physical or chemical change is the same.
Matter cannot be created or destroyed
The particles inside the matter rearrange to form new substances
Law of Conservation of Mass
Even though it appears that part of the candle disappears, it is just turned into a gas.– proven by Antoine Lavoisier
The Law of Conservation of MassThe law states that the total mass of the
matter is the same before as after any physical or chemical change.
Does that surprise you?That means everything that is here now- all of the matter- has always been here . This is all of the matter we have- in our universe
Does that surprise you?That means everything that is here now- all of the matter- has always been here . This is all of the matter we have- in our universe
ActivityLets practice using these words:
Procedure
1.Draw and label the physical properties of your piece of matter
2.Label any of the parts of your matter that have a chemical property
3.Make the matter change (wait for us)
4.Describe all physical and chemical changes (draw the after and label)