Factors Affecting Chemical Reactions

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Good morning,


I apologize for not being here! I am at a conference in Vancouver called Crosscurrents.  I have to go to school every once in a while too!


Super congrats to all of you that took the last test.  The average was higher than a C+ so I do owe you a party. Unfortunately it will have to wait until after spring break. 

Back to science!


So you remember that chemical reaction you did with hydrogen peroxide and yeast?? The one that foamed like crazy?  Well we are going to learn about why that happened today.  This section starts on page 113 of your workbooks. Open it now. Do it!


So a reaction can happen slowly or quickly. How fast this happens is called the Rate of Reaction.  A rate explains how slow or fast a change occurs.


There are some things that can change the RATE, or how fast or slow something happens.


1.Temperature.  

Just like when you are sloth like in the early, cold morning, atoms and molecules move around slowly when cold.  This means that they take more time to bump into each other and it takes longer for reactions to occur.  On the other hand, when molecules are HOT, they race around, bumping into each quickly, making reactions happen FAST!  Watch this:




Pretty cool eh!? I tried to find some glow sticks but couldn't so this will have to do.  

In short, reactions happen fast when hot, slow when cold. REMEMBER THIS!!

2. Concentration

You know when you make orange juice from the frozen containers and how delicious it is all depends on how much water you put in?  If you are like me then you put very little water in so it does not taste bland.  The amount of orange juice you put in for a set amount of water is called: CONCENTRATION.


Reactions happen faster with higher concentration (less water and more orange juice!) Check this out:




Hey, you remember doing the first part of that experiment?? Unfortunately we don't have 30% hydrogen peroxide to make the cool stuff.  We are going to order some this summer so if you want to see the demo next year I will let you know when it happens.  

So remember this: The higher the concentration, the faster the reaction. Got it? Good.

3. Surface Area
 This is a measure of how much area is exposed on an object.  Let's take a sugar for example.  A sugar cube has a much smaller surface area than the same amount of loose sugar grains.  Check out this cheezy video.




4. Catalysts

Remember adding yeast to the hydrogen peroxide to make it bubble? A bunch of you asked what the yeast was for.  Well, here is your answer. The yeast was a CATALYST.  This is a substance that speeds up the rate of a reaction.  It is not actually used up in the reaction.  Another example of a catalyst would be enzymes in our bodies.

Now for the fun stuff.  You should already be working on Workbook pages:  105-111. Now in addition, I want you to work up to Page 119.  

Workbook pages 105-119.  I am going to really focus on pages 111 and 119.

Have a great spring break and be safe!!!