PHYSICAL AND CHEMICAL CHANGES
Third Year Level
Preciosa V. CabreraIsmael Mathay Sr. High School
Objectives:
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
At the end of the lesson, the students should be able to:
1. Differentiate physical change from chemical change.
2. Describe what happens to a substance that undergoes chemical change.
3. Identify the signs of chemical change in a reaction.
Properties of Matter
Physical properties: • do not change the chemical nature of matter.• examples: color, smell, freezing point, boiling
point, temperature, density, viscosity Chemical properties: • change the chemical nature of matter.• examples: heat of combustion, reactivity with
another substance, toxicity, flammability
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
•anything that has mass and volume
To understand changes in matter, you need to be able to describe and classify the sample• before the change and• after the change
Matter
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
• Physical change
• Chemical change
There are two changes in matter
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
• occur when a substance changes its appearance without changing its composition.
• phase change.
Physical Changes
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Phase changes in matter
http://www.clickandlearn.org/images/water_cycle.gif
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Chemical Changes
http://www.ric.edu/faculty/ptiskus/chemical/
Chemical changes are changes substances undergo when they become new or different substances. Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
The fireworks we see during New Year’s Eve are actually metals such as magnesium and copper that change chemically as they light up the night skies with their fantastic colors.
Fireworks
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Evidences of Chemical Change
• Change in intensive
properties such as
odor, color and taste
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Change in temperature
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Formation of a solid substance or precipitate
http://www.ric.edu/faculty/ptiskus/chemical/
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Production of heat or light
http://www.ric.edu/faculty/ptiskus/chemical/
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Production of mechanical energy
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
paper
Evolution of gas or formation of bubbles
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Production of electrical energy
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Activity
Materials: pieces of paper test tubes styrofoam watch glass acetone pair of scissors vinegar dropper NaHCO3 match milk modeling clay
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Procedure
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
2. Mold the modeling clay into different shapes. Observe.
3. Cut the styrofoam into pieces. Place the cut styrofoam in the watch glass and add a few drops of acetone. Observe what happens.
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
4. Put about 10 mL of vinegar in two test tubes. Add a pinch of sodium bicarbonate in one test tube and 5 mL of milk in another. Observe what happens in both test tubes.
5. Enter your observations in the table below.
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Data and Observation
System Observation Physical or Chemical change
Signs of Chemical change
1. Cutting paper
2. Burning paper
3. Molding clay
4. Cutting Styrofoam
5. Styrofoam and acetone
6. Vinegar and NaHCO3
7. Vinegar and milk
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
1. Can physical and chemical changes occur in a system at the same time?
2. What is the difference between a physical change chemical change?
3. What patterns of evidence do you note in your observations of physical change? of chemical change?
A. Guide questions
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
1. formation of clouds2. burning of plastic3. corrosion of iron 4. sublimation of iodine crystals5. decaying of food
B. Identify the type of change. Justify your answer.
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Summary of the lesson
Physical Change
There is only a change in phase
Change in the appearance of the substance
Chemical Change
Change in the
properties of the
substance. The substances
formed are different from the original substance.
Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09
Original substance can be recovered
The substances are the same before and after the change
Original substance can not be recovered
The substances are not the same before and after the change