3.28 instructions chemical physical changes

7/29/2019 3.28 Instructions Chemical Physical Changes

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1. Read and answer the questions on this

ppt.

2. Go to Brainpop

http://www.brainpop.com/science/mattera

ndchemistry/propertychanges/

Watch the video Property Changes. Then,

take the quiz.3.Read and answer the question on the ppt

Chemical and Physical Properties.


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Chemical changes are changes that involve

the creation of new substances. What newsubstances are created here?

Chemical changes also involve the

formation of new chemical bonds.


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Chemical changes cannot be undone

without a chemical reaction. For example,you cannot unburn paper or unexplode

fireworks or sodium. You cannot unrust

iron.

Common chemical changes: rusting (also

called oxidation or corrosion), explosions,

burning, leaves changing color, an appleturning brown.


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1. Color change (not always, though)2. The beaker or container feels hot or cold

(always)

3. Explosion (always: make sure it is a true

explosion)

4. Bubbles (almost always)

5. Rotting (always), growth (always),

cooking (always) or digestion (always)6. A precipitate is formed (always)

These are also signs of a chemical reaction!


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You are observing a chemical change,because a chemical reaction is happening:

A new substance is being made.

Lead Iodide reaction:

Pb(NO3)2(aq) + 2KI(aq) PbI2(s) +

2KNO3(aq)

Why is this a chemical change?

New molecules are being made. One ofthem is the yellow precipitate, PbI2(s).


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In a physical change, no new substance or

molecule is created. There is no chemical

reaction, meaning that no chemical bonds

are broken or made.

A physical change, unlike a chemical

change, CAN be undone.


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1. Substance A dissolving into Substance B (ex:salt dissolving into water). The salt molecules

are just spreading out among the water

molecules: phet simulation

2. A substance is broken, torn up, cut, sliced, etc.You are breaking the substance, NOT the

chemical bonds between the molecules of the

substance.

3. Food coloring in water.

4. Phase changes: Melting, Boiling, Freezing,

Condensing: phet simulation


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Practice:

Determine whether the following are chemical or

physical changes: 1. Sodium hydroxide dissolves in water.

Chemical Change


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2. Hydrochloric acid (HCl) reacts with

potassium hydroxide (KOH) to produce asalt (NaCl), water (H2O), and heat.


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3. A pellet of sodium is sliced in two.


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4. Water is heated and changed to steam.


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5. Potassium chlorate (KClO3)decomposes to potassium chloride (KCl)

and oxygen gas (O2).


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6. Iron rusts


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Complete the worksheet. As you are

completing the worksheet, in your ISN,

draw what is happening to the molecules

for each question and explain why your

pictures shows that it is a physical or

chemical change.

3.28 instructions chemical physical changes

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