Chemical and Physical Changes

Grade 5 

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Be Prepared the be EMAZED

Science Standard 1

Students will understand that chemical and physical changes occur in matter.

Objective 2

Evaluate evidence that indicates a physical change has occurred.

Identify the physical properties of matter (e.g. solid, liquid, gas). 

1. Compare changes in substances that indicate a physical change has occurred. 
2. Describe the appearance of a substance before and after a physical change. 

Objective 3 

Investigate evidence for changes in matter that occur during a chemical reaction.

Identify observable evidence of a chemical reaction (e.g., color change, heat or light given off, heat absorbed, gas given off).  Explain why the measured weight of a remaining product is less than its reactants when a gas is produced.  Cite examples of chemical reactions in daily life.  Compare a physical change to a chemical change.  Hypothesize how changing one of the materials in a chemical reaction will change the results.  Ed Tech Standards: Standard 8  Use technology resources (e.g., calculators, data collection probes, videos, educational software) for problem-solving, self-directed learning, and extended learning activities.  This topic to be discussed over three to five weeks.  I used eMaze to create a slide show for my students.  I will have my students watch the slide show before the start of class or they can watch it at home as many times as they want.  I loved using eMaze.  It was easy to use and quick to put together.  I will be using this again.

Activity #1 At the start of class I will ask students how I can change the appearance of a sheet of paper.  I will do what they say i.e. rip paper, draw on paper, tear paper, burn paper.  Then show the class what happened.  And discuss what change occurred.  I will write on the board: 

• A physical change is when a material keeps it identity.  
• A chemical change is one substance or kind of matter changes completely into another substance or matter.

Go over safety while doing experiments.  No tasting, touching with fingers, safety goggles, etc.  I will perform the following experiments and discuss with the class the changes and what they are:

• Balloon popping-Physical change
• Polyurethane-chemical change

The students will perform experiments in groups and discuss what changes they see and record their findings: 
Worksheet #1      Worksheet #2

• Steal wool  
• Fake snow
• Baking soda and calcium chloride- chemical change

steel wool and vinegar experiment

Activity #2
Experiments Root beer Floats 

Take one glass and put a generous scoop of ice cream in it. In the another glass, fill it half full of root beer.  Ask students about their predictions about what the differences will be when you finish off these floats. 

• Will they look the same, and if not, what will be the differences?  

When the ice cream is added to the soda it doesn't create as many bubbles as when the soda was added to the ice cream.  In either case, when the ice cream and the root beer meet, the gas trapped in the root beer is released into a lovely bubble foam.  A lovely physical change.  

You are knocking the carbon dioxide in the soda out of solution. Bubbles of carbon dioxide do something called nucleation shortly after the pressure is released from a container of carbonated liquid. Nucleation is a reaction which occurs when components in a solution start to precipitate out, forming nuclei which attract more precipitate. Nucleation often occurs more easily at a pre-existing interface (a point of interaction between two systems) such as the ice cream.  Some ingredients in the ice cream lower the surface tension of the soda so the gas bubbles can expand, while other ingredients trap the bubbles in much the same way as small amounts of protein in seawater trap air to form seafoam.

So, when the ice cream is added to the soda, the soda had time to release most of the carbon dioxide into the air before the ice cream was added, but when the soda was added to the ice cream, the ice cream provides nucleation sites around which the carbon dioxide bubbles could form and grow.

Here are more experiments for in class.

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