Physical and Chemical Changes
Qualitative Observations- Observed using our 5 senses Qualitative Observations- Observed using our 5 senses. Quantitative Observations- Observations using numbers (counting, measuring)
Physical changes Indicators of a Chemical change (p.22)
Physical Change (p.21) In a physical change, you do not get anything new. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings
Physical changes- Indicators of a Chemical change (p.22) Change in matter, but you do NOT get a new substance
What is a Physical Change? A physical change is a change in which no new substance is formed, but properties may be changed.
What is a Chemical Change? A chemical change is a change in which a new ________ with new _________is formed. substance properties
Physical changes Indicators of a Chemical change (p.22) Change in matter and a NEW substance is formed
Take your paper and crumple it. Do you have something new? No, it is still paper although it looks somewhat different.
If shape changes, then you’re observing a _______ change… physical
Physical changes Indicators of a Chemical changes Change of shape
Take your paper and rip it into 2 pieces. Do you have anything new? No, it is still paper although it looks somewhat different.
If you observe a change in size, then you’re observing a _______ change… physical Wet sponge Dry sponge
Physical changes Indicators of a Chemical changes Change of shape Change in size
Looking at the ice…..it has melted. Do I have anything new? No! It is still water. It has just changed its state from a solid to a liquid.
If you observe a change in state, then you’re observing a ________ change… physical
Physical changes Indicators of a Chemical changes Change of shape Change in size Change in state of matter
Measure out a ½ teaspoon of baking soda and put it into a cup. Add 3 pipettes of vinegar. Was something new produced? YES! Bubbles were produced. That indicates a gas was made. The gas is a new substance.
If you observe bubbling (not due to boiling or shaking), then a _______change is occurring… chemical
chemical If you observe fizzing, then you will know that a _________ change is occurring (unless you shook the substance)…
Physical changes Indicators of a Chemical changes Bubbles/fizzing are produced Change of shape Change is size Change in state of matter
Rinse out cup and refill 1/2 way with water. Add one drop of food coloring to the water.
Was the colored changed? Did you get anything new? Adding a certain color to a substance and it changing that color is only a physical change. That is what you expected and wanted to occur.
Take a glass of clear water from near the sink. Pour the cup of colored water into the cup of clear water. Was the colored changed? Did you get anything new? No, you just made the colored water not as dark. You diluted it.
Physical changes Indicators of a Chemical changes Bubbles/fizzing are produced Change of shape Change is size Change in state of matter Diluting
Rinse out small cup and refill 1/4 way with water Rinse out small cup and refill 1/4 way with water. (Just leave large cup on counter)
Add a piece of Alka-Seltzer to your cup of water Add a piece of Alka-Seltzer to your cup of water. Quickly place a finger into the cup. Did you get anything new? Did you feel any temperature change?
Physical changes Indicators of a Chemical changes Bubbles/fizzing are produced Change of shape Change is size Change in temperature Change in state of matter Diluting
When we burn something….. Is a new substance produced? Yes, soot is produced or ashes.
If you smell burning, then you know that a change is _________ occurring… chemical
If you SEE burning, then a _________ change is occurring… chemical
Physical changes Indicators of a Chemical changes Bubbles/fizzing are produced Change of shape Change is size Change in temperature Change in state of matter Burning or cooking Diluting
Is melting a chemical or physical change?
If I add salt to water, can I separate them back into water and salt? YES! It is a mixture. So physical or chemical change?
Why? When a substance is not changed into a new substance, the change is only physical.
Physical changes Indicators of a Chemical changes Bubbles/fizzing are produced Change of shape Change is size Change in temperature Change in state of matter Burning or cooking Diluting Dissolving
Rusting? In a chemical reaction, old bonds are broken and new bonds are formed. A NEW SUBSTANCE IS FORMED. Fe and O2 form rust (Fe2O3).
Dirty silver?
Physical changes Indicators of a Chemical changes Bubbles/fizzing are produced Change of shape Change is size Change in temperature Change in state of matter Burning or cooking Rusting/ tarnishing Diluting Dissolving
If you observe that matter is__________, then a __________change is occurring… decaying chemical
Physical changes Indicators of a Chemical changes Bubbles/fizzing are produced Change of shape Change is size Change in temperature Change in state of matter Burning or cooking Rusting/ tarnishing Diluting Odor produced/ decay Dissolving
Mixing chemicals…. Glow stick What was observed? Pour 15–20 mL of copper II sulfate solution into a test tube so it is about ½ full. Add about 10–20 drops of ammonia. Add about 10–20 drops of hydrogen peroxide.
We said that adding a certain color to a substance and it changing that color is only a physical change. That is what you expected and wanted to occur. But….
Physical changes Indicators of a Chemical changes Bubbles/fizzing are produced Change of shape Change is size Change in temperature Change in state of matter Burning or cooking Rusting/ tarnishing Diluting Odor produced/ decay Dissolving Change of color/ light produced
Physical changes Indicators of a Chemical changes Bubbles/fizzing are produced Change of shape Change is size Change in temperature Change in state of matter Burning or cooking Rusting/ tarnishing Diluting Odor produced/ decay Dissolving Change of color Precipitate formed
What was formed was a precipitate What was formed was a precipitate. Precipitate - a solid formed by mixing two or more liquids.
If you observe explosions because of burning, then a ________ change is occurring… chemical
If you observe cooking, then a _______change is occurring… chemical
If you observe bending (of metal, for example), then a __________change is occurring… physical Pulling metal into wires is called _________ ductile
If you observe reshaping (into a tube, for example), then a _______change is occurring… physical
If you observe pounding metal into sheets, then a _________change is occurring… physical This is called ______________. malleable
If you observe cutting, then a __________change is occurring… physical
If you observe melting, then a _______change is occurring… physical
If you observe rusting, then a ______change is occurring… chemical Note: Rusting occurs when some metals react with the element Oxygen, which is in the air. For this reason, rusting is also called oxidation.
If you observe cooling because refrigeration was added, then a _______change is occurring… physical
If you observe warming without the use of fire or a heater, then a ________change is occurring… chemical
If you observe warming with the use of fire or a heater, then a _______change is occurring… physical
If you observe new matter being made, then a _________change is occurring… chemical
Indicators of chemical reactions: Production of a gas Change in color New substance produced Change in the chemical formulas Heat is produced or absorbed Odor is produced
Some Examples of Chemical and Physical Changes
Learning Check 2 1 2 1 2 Classify each of the following as a 1) physical change or 2) chemical change. A. ____Burning a candle. B. ____Ice melting on the street. C. ____Toasting a marshmallow. D. ____Cutting a pizza. E. ____Polishing a silver bowl. 2 1 2 1 2
Properties of Matter observations/ changes observations/ changes Physical Chemical State of matter solid, gas, etc Melting Point Gas produced Decaying Density Taste Precipitate formed Flammability Burning Hardness Diluting Color change Tarnishing Breaking/ ripped Odor Temperature change