Student ObjectiveIdentify the indicators that a chemical change/reaction

has occurred.

Warm Up

WHAT DO YOU THINK????• How do you know if a chemical reaction has taken

place??

Add to Physical vs Chemical Notes

4.A PHYSICAL change affects only the _____________________ of the material, but does not make a _______ _________________.

5.A CHEMICAL change forms _______ or more __________ substances.

Matter can undergo two kinds of changes…. PHYSICAL changes and CHEMICAL changes.

Physical Change a change that affects only the appearance of a material, but does not make a newsubstance.

Differences between chemical and physical changes…

Chemical Change a change that forms one or more new substances.

Add this to your worksheet & to your vocab. section!!

Add 2 examples to 3rd box on vocab. paper from next two slides

Examples of Physical Changes….Why?

tearing paper

chopping wood

molding clay

melting ice

                                      

raw egg becomes cooked

egg

                                    

         

                      

cake mix

becomes cake

         

                             

              

                        

paper becomes

ash

                                     

 

                                            

 

steel becomes

rust

                                       

      

EXAMPLES OF CHEMICAL CHANGES….Think about why each of these is a “chemical change”.

How do you know if a chemical reaction has taken place and a

new substance is made?

Use the following slides to find out as you complete your “Indicators of a Chemical Change or Reaction” worksheet

Indicators of a Chemical Reaction Occurring:

•Sometimes a gas is produced, which you might see as bubbles in a liquid.

•Other times, a solid may appear when two solutions are mixed. A solid that forms from mixing two solutions during a chemical reaction is called a precipitate.

Indicators of a Chemical Reaction Occurring:

Still other times, a color change or a change in other properties may tell you that a new substance has formed.

Indicators of a Chemical Reaction Occurring:

Sometimes heat and/or light are produced when a new substance is formed.

Indicators of a Chemical Reaction Occurring:

All of these indicators are evidence of a chemical reaction. But they do not always mean that a chemical reaction has taken place. Sometimes, physical changes give similar results! Take for example boiling water. Don’t you observe bubbles indicating a gas has been made, but is it a new substance? In this case, the liquid water has turned into gas water……it’s still water! Just a change in state has occurred, not the creation of a new substance!

The key characteristic of a chemical reaction is the production of new substances that are chemically

different from the starting substances!

REVIEW: INDICATORS OF A CHEMICAL REACTION

Color Change:

PrecipitateGas Produced

Temperature change

Light produced

(List these at the bottom of your worksheet)

Touching Cactus Gives Little Pricklies.

Virtual Lab: Reversible & Irreversible changes. http://www.bbc.co.uk/bitesize/ks2/science/materials/change

s_materials/play/ Click yellow “Fullscreen” button Sound off, subtitles on When you have completed the mission click yellow “Close”

button & then scroll down to find QUIZ.

Fill-in-the-Blanks

*Reading Comprehension - Properties and Changes

Try these sites to see if you and your partner really know about physical and chemical changes.

•http://www.edinformatics.com/math_science/a_p_chem.htm

•http://www.quia.com/quiz/303980.html

Conclusions:

Where’s the Evidence of a Chemical Reaction?

Look at the reactions on the next chart. Fill in the last two columns by putting your answers on your worksheet.

Where’s the Evidence? ActivityReaction Observations

Before Reaction

1. Sodium carbonate (powder) + hydrochloric acid

       

2. sugar + heat     

     

3. Copper sulfate + sodium carbonate solutions

 

     

Observations

After Reaction

Describe the change that occurred

Was there a chemical reaction?

Indicators?

Where’s the Evidence? ActivityReaction Observations

Before Reaction

1. Sodium carbonate (powder) + hydrochloric acid

       

2. sugar + heat     

     

3. Copper sulfate + sodium carbonate solutions

 

     

Observations

After Reaction

Describe the change that occurred

Was there a chemical reaction?

Indicators?

• turned white

• bubbles formed

• turned brown

• looks liquidy

• thick stuff formed in the clear liquid• 2 clear liquids turned blue

YES

• color change

• gas produced

YES• color change

YES

• color change

• precipitate formed