Physical vs. Chemical Changes - cf.edliostatic.comcf.edliostatic.com/t78DBWlHyYlcpQ4rqybqXCSJn1hoxY2x.pdf · a chemical or physical change? •Can changes happen outside of the science

Physical vs. Chemical Changes

Warm-up 6 March 2013

From the “Cooking with Chemistry” activity, describe how did you use phase change to complete the final task of separating the salt from the solution?

http://whatscookingamerica.net/Foto4/BoilingWater.bmp

-L

3/6/2013 Review of Previous Knowledge

______ 1. Aluminum can be flattened into sheets of foil. ______ 2. Water is frozen into ice. ______ 3. Copper can be pulled into thin wires. ______ 4. Your hand grows warm from holding a cup of

hot liquid. ______ 5. Flavored drink mix dissolves in water. ______ 6. An onion gives off a very distinctive smell. ______ 7. A golf ball has more mass than a table tennis

ball.

State solubility thermal conductivity

Malleability odor ductility

density

Physical Property: Chemical Property:

Example: Example:

Physical Change:

Chemical Change:

Example:

Example:

Signs of a physical change: Signs of a chemical change:

What’s the Difference?

Matter can change

Examples: Freeze, cut, burn, etc.

2 types of changes

1. Physical changes

2. Chemical changes

Physical Property

Characteristic of matter

that does not change the

substance (using senses)

Physical Changes

Matter changes form WITHOUT becoming something new – You start and end with same thing (see below)

Examples: cutting, freezing, melting, etc.

Molecules in Physical Changes

Chemical Property

Describes matter on its ability to change into new matter

– Flammability: ability of substance to burn

– Reactivity: ability of substance to change into new substance

Chemical Changes

Matter changes, becomes NEW substance

– Start and end with different things

Usually irreversible (can’t change back)

Examples: burning, rusting, milk going sour

Signs of Change

Physical

– Size

– Shape

– Texture

Chemical

– Temperature

– Color

– Bubbles/fizzing

– Smoke

– Smell

Reactants:

Products:

Chemical Change = _________________ In chemical changes, atoms and molecules re-arrange to form new substances.

Molecules in Chemical Changes

The atoms

arrange to make

a new substance

Chemical Change = Reaction

Products: the resulting

solutions in a reaction

Reactants: starting


______________

• Liquid • • •

____________

• Powder/dry • • •

I noticed the ……

Mixing Things Up: Chemical Change Demos Observations of Reactants:

•Observations during the demonstration:




Reactants: starting


Question Answer

A chemical reaction between two materials occurs if the properties of the products (what you make) are different from the reactants (what you mix). Was what you observed today a chemical reaction? Explain!




Reactants: starting


Chemical reactions have formulas just like molecules and compounds. As a class, we will write the chemical equation below and label the reactants and the products.

Reactants:

Products:

Reactants:

Products:

Chemical Formula

In words

Chemical Reaction Demo

NaHCO3 NaOOCCH3

+ HOOCCH3 + H2O + CO2

Sodium Acetate,

water, and carbon

dioxide

Sodium

Bicarbonate and

Acetic Acid




Reactants: starting


Summary:

• How can you tell if a chemical reaction happened?

• What are evidences to support that chemical reaction happened?

• After a chemical reaction will it be possible to bring back the reactants to their original form (state and properties)?

• How is chemical reaction related to chemical change?

Signs of Chemical Change

Fizzing/gas formation

Flash/light smoke

Change in temperature

Smell/odor Change in color


Give an example of a physical change and a chemical change, and then describe how they are different from the other. Explain your answer in 2-3 sentences.


Why is cooking/baking similar to science? Explain your answer.

-L

3/6/2013 Review of Previous Knowledge

Match the following description with the list of terms below. ______ 1. Thermal energy is given off. ______ 2. Precipitate forms. ______ 3. Nitrogen dioxide forms. ______ 4. Bleach spots form.

color change

energy change

solid formation

gas formation

Physical Change v. Chemical Change

Make a Venn Diagram to compare the 2 types

of changes

Physical

• Does not

change to new

substance

• Size, shape

and texture

(physical

properties)

• Cutting, phase

change

Chemical

• Molecules

rearrange to

form new

substance

• Signs; color,

temperature,

smoke, etc.

• Burning,

rusting

changes

Physical Change vs. Chemical Change

Objective To correctly identify and differentiate physical change from chemical change.

Question Are changes (physical and chemical) only present inside the laboratory? How are physical change different from chemical change?

Hypothesis If physical change does not produce a new product, then I can ….




Reactants: starting


Steps Physical or Chemical

Observations:




Reactants: starting



Breaking graham crackers

Observations:




Reactants: starting




Breaking chocolate bar

Observations:




Reactants: starting





Cooking Marshmallow

Observations:




Reactants: starting





Cooking Marshmallow

Stacking cracker, chocolate,

and marshmallow

Observations:




Reactants: starting





Cooking Marshmallow


and marshmallow

Chocolate melting

Observations:




Reactants: starting





Cooking Marshmallow


and marshmallow

Chocolate melting

Eating smore!

Observations:




Reactants: starting


Discussion/Summary:

• How will you know if an object underwent a chemical or physical change?

• Can changes happen outside of the science classroom or laboratory?

Physical Change v. Chemical Change

Make a Venn Diagram to compare the 2 types

of changes

Is it a chemical or physical change?

Sugar dissolving in

tea

•Chemical Change

•Physical Change

OOPS!

Did it change size, color, shape (Physical Change)?

or

Did it become different matter (Chemical Change)?

Correct!


Logs burning

•Chemical Change

•Physical Change

OOPS!


or


Correct!


Breaking water up by

separating it into hydrogen

and oxygen

•Chemical Change

•Physical Change

OOPS!


or


Correct!


Cutting paper

•Chemical Change

•Physical Change

OOPS!


or


Correct!


Crushing an

aspirin

•Chemical Change

•Physical Change

OOPS!


or


Correct!


Metal rusting

•Chemical Change

•Physical Change

OOPS!


or


Correct!


An egg rotting

•Chemical Change

•Physical Change

OOPS!


or


Correct!


An egg breaking

•Chemical Change

•Physical Change

OOPS!


or


Correct!

Standards 8.5.c.

I know chemical reactions

usually liberate or

absorbs heat.

Endothermic and Exothermic Reactions

When chemical reactions occur, the

connections between atoms must be

broken and rearranged. In order to do

this, ________________ is involved in

all chemical reactions.

Heat

There are 2 Types of Reactions Involving Heat

Endothermic Exothermic

• Within-Heating • Endo = Enter • Therm/ic = Heat

• Outside-Heating • Exo = Exit • Therm/ic = Heat

There are 2 Types of Reactions Involving Heat (cont.)


• Reactions in which the system absorbs heat from the surrounding.

• Reactions in which the system releases heat to the surrounding.



It feels: It feels:

Cold Hot



Examples: Examples:

• Cooking an egg • Baking a bread

• Candle flame • Rusting Iron

Frayer Model

Exothermic

Reaction

Frayer Model

Endothermic

Reaction




Reactants: starting


Weekly Reflection/Exit Slip

• Name 4 items you learned in this week’s lesson.

• If Mr. Rivera will teach the lesson again, will you want it done differently?

• If you want it done differently, why and how would you want it?

• If you want it done the same, why?

Documents

Physical vs. Chemical Changes - cf.edliostatic.comcf.edliostatic.com/t78DBWlHyYlcpQ4rqybqXCSJn1hoxY2x.pdf · a chemical or physical change? •Can changes happen outside of the science