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

Physical Change In a physical change, you do not get anything new. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

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

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 1/3 way with water.

I will pour the cup of water into the cup of colored 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

Add a piece of Alka-Seltzer to your cup of water Add a piece of Alka-Seltzer to your cup of water. Quickly place hand on side of cup for 3 seconds. 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.

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