Changes in Matter : Changes in Matter Adapted from Chemical Interactions
Discover Activity : Discover Activity Obtain a small piece of chalk. Observe it and record its properties in your notebook.
Place the chalk on a piece of paper and crush it with the back of a spoon. Record the changes that occurred in your notebook
Discover Activity (Cont.) : Discover Activity (Cont.) Place some of the crushed chalk into the bowl of the spoon. Add about 8 drops of vinegar. Record what happens in your notebook.
Explanation : Explanation Chalk is mostly a single substance, calcium carbonate. Do you think a new substance was formed when the chalk was crushed?
Do you think a new substance was formed when vinegar was added? Provide evidence for your answers.
Chemistry : Chemistry The study of matter and it’s changes.
Physical Changes : Physical Changes Changes that alter the form or appearance of matter.
Does not change the substances in the matter into new substances.
Examples of Physical Changes… : Examples of Physical Changes… Changes in State
When matter changes from a solid to a liquid or a liquid to a gas.
Ice/water vapor/liquid water
Dissolving
Bending, crushing, breaking, chopping
Check for understanding : Check for understanding Why is the melting of an ice cube called a physical change?
The substance is still water, just the form has changed.
Chemical Change : Chemical Change Occurs when a substance is transformed into a different substance.
The newly formed substances have different properties than the original substances.
Examples of Chemical Changes… : Examples of Chemical Changes… Combustion
Electrolysis
http://jchemed.chem.wisc.edu/JCEsoft/CCA/CCA3/MAIN/ELECH20/PAGE1.HTM
http://video.google.com/videoplay?docid=-4806079481951573184&q=electrolysis+of+water&hl=en
Oxidation
Tarnishing
Evidence for Chemical Reactions… : Evidence for Chemical Reactions… Color Change
Precipitation
Gas production
Temperature changes
Changes in properties
Conservation of Mass : Conservation of Mass What happens to a candle as it burns?
LAW of conservation of mass states that MATTER IS NOT CREATED OR DESTROYED IN ANY CHEMICAL OR PHYSICAL CHANGE.
Matter and Thermal Energy : Matter and Thermal Energy ENERGY is the ability to do work or cause change.
Every chemical or physical change in matter includes a change in energy.
Thermal Energy Changes in matter : Thermal Energy Changes in matter When matter changes, the most common form of energy released or absorbed is thermal energy.
ENDOTHERMIC changes
absorb energy
EXOTHERMIC changes
give off energy
Review : Review Identify three different kinds of physical changes that could happen to a crayon.
2. Which of the following is not a physical change:
Drying wet clothes
Cutting snowflakes out of paper
Light a match
Review : Review 3. What evidence would you look for to determine whether a chemical change had occurred?
4. Why is the electrolysis of water classified as a chemical change but the freezing of water is not?
Review : Review 6. What is thermal energy?
7. How can you tell whether one glass of water has more thermal energy than another, identical glass of water?
8. Explain why a change in temperature does not always mean a chemical change has occurred.
Credits : Credits Chemical Interactions, Pearson Prentice Hall, 2005, Boston, MA