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 Changes changing 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 Changes change of shape Matter can change shape cutting tearing grinding crumpling bending

Physical Changes dissolving 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 change

More signs of a chemical change Takes 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 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. 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) 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 SrCO 3. Sr 2+ (aq) + CO 3 2- (aq) SrCO 3 (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

Is the change reversible? Folding paper? Tearing your shirt? Cutting your hair? Eating an apple? Burning some wood? Cooking chicken?

Chemical Changes Iron + oxygen and water = rust silver + oxygen and water = tarnish

Chemical Changes Burned wood Cooked food

Chemical Changes Leaves turning in fall Spoiled food

Chemical Changes Lightning bug Antacid tablet

Physical or Chemical Copper jewelry Statue of Liberty orangeOrange juiceOrange cake copper Physical Chemical PhysicalChemical

Law of Conservation of Mass The 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 Mass The 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

Activity Lets 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)