PHYSICAL AND CHEMICAL CHANGES Third Year Level Preciosa V. Cabrera Ismael 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 Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09

Chemical Changes 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 Preciosa V. Cabrera Ismael Mathay Sr. High School 10/16/09

Production of heat or light 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 papertest tubes styrofoamwatch glass acetonepair of scissors vinegardropper NaHCO 3 match milkmodeling 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 SystemObservationPhysical 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 NaHCO 3 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 clouds 2. burning of plastic 3. corrosion of iron 4. sublimation of iodine crystals 5. 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