Discussion: What’s New? Physical or chemical change? What is true about the kinds of matter present before and after a physical change? How is matter different? What is true about the types of matter present before and after the matter undergoes a chemical change What substances were formed when the paper burned? Would it be possible to change these types of matter back into a sheet of paper?

Matter is described by its properties and may undergo changes Big Idea: Matter is described by its properties and may undergo changes Unit 1 Lesson 3 Physical and Chemical Changes Essential Question: What are physical and chemical changes of matter? Copyright © Houghton Mifflin Harcourt Publishing Company

P36-39 What are physical and Chemical Changes of Matter? Physical Changes Chemical Changes

Change of Appearance Physical Changes P36 - 38 Unit 1 Lesson 3 Physical and Chemical Changes Change of Appearance Physical Changes A physical change is a change that affects one or more physical properties of a substance. The appearance, shape, or size of a substance may be altered during a physical change. Physical changes, such as changes in state, do not change the chemical identity of a substance. 5) Physical properties of the substance are changed. 7) Yarn was twisted, dyed, and knit to form sweater – it’s still wool.

Change of Appearance P38-39 Chemical Changes Unit 1 Lesson 3 Physical and Chemical Changes Change of Appearance Chemical Changes A chemical change is the process when one or more substances change into entirely new substances with different properties. A substance’s identity changes because the chemical makeup changes. Bonds get rearranged and/or new bonds form. Influenced by temperature: At higher temperatures, chemical reactions happen more quickly

P38-39 8) Flames wood Ashes Smart Activity 9) Raising temp causes particles in matter to move more quickly. Increased motion causes particles to bump into each other which increases the rate of the chemical reaction 8) Burning wood is an example of a chemical change in which wood is transformed into new substances, such as ash and smoke

Change into entirely new substances with different properties No change in Identity Occur in matter PROCESS Bonds broken or new bonds form Affects Physical Properties Changes appearance Physical Changes Chemical Changes LAW OF CONSERVATION Chemical Makeup changes Change in appearance, shape or size

Law of Conservation of Mass . Law of Conservation of Mass P42-43

Conservation Is the Law P42 - 43 Unit 1 Lesson 3 Physical and Chemical Changes Conservation Is the Law What is the law of conservation of mass? French chemist Antoine Lavoisier studied chemical changes in which substances appeared to gain or lose mass. The law of conservation of mass states that in ordinary chemical and physical changes, mass is not created or destroyed. It is only transformed into different substances.

What is the law of conservation of mass? P42 - 43 Unit 1 Lesson 3 Physical and Chemical Changes What is the law of conservation of mass? Most physical changes are reversible and follow the law of conservation of mass. Mass is conserved during chemical changes. The mass of the starting materials is the same as the mass of the end products. Chemical Change

Law of Conservation of Mass . Law of Conservation of Mass Antoine Lavoisier chemical and physical changes mass is not created or destroyed. Mass is conserved during chemical changes Physical changes can be reversible The mass of the starting materials is the same as the mass of the end products.

Look for the Signs How can you tell a chemical change has happened? Unit 1 Lesson 3 Physical and Chemical Changes Look for the Signs How can you tell a chemical change has happened? There are several signs that a chemical reaction has occurred. Observing two or more of these signs during a change means you are likely observing a chemical change.

P40-41 How do you know a chemical change has happened? if you observe two or more signs… you likely are observing a chemical change P40-41

Careful! How can you tell a chemical change has happened? p40 - 41 Unit 1 Lesson 3 Physical and Chemical Changes How can you tell a chemical change has happened? Odors can be produced during a chemical change. Fizzing and foaming may mean gases are being produced. The production of gas is often evidence of a chemical change. Boiling also can produce gas bubbles, but boiling is a physical change. Careful!

How can you tell a chemical change has happened? Unit 1 Lesson 3 Physical and Chemical Changes How can you tell a chemical change has happened? A precipitate is a solid formed from liquids. The formation of a precipitate can indicate a chemical change. Energy that changes from one form to another can be evidence of a chemical change. Changes in temperature and color can be signs of a chemical change.

Change Signs/Observations Type of Change Boiling Water Bubbles formed No new substance formed physical Baking a Cake Odor, change in energy, color change chemical Burning Wood Change in energy, color change, wood  ash Painting a door Color change No new substance is formed

How do you know a chemical change has happened? if you observe two or more signs… you likely are observing a chemical change Production of a Gas Production of an Odor Change in Color Change in Energy Precipitate Forms Energy changes form/ Temperature change Rotting egg = sulfur smell Fizzing or Foaming 2 liquids combine to form a solid Gray iron forms brown rust Antacid tablet in water produces carbon dioxide Sour milk – bacteria formed a new substance Chemical energy converts to light and heat

Physical or Chemical Change? Part B Read each scenario. Decide whether a physical or chemical change has occurred and give evidence for your decision. The first one has been done for you to use as an example.   Scenario Physical or Chemical Change? Evidence… 1. Yumm! A student removes a loaf of bread hot from the oven. The student cuts a slice off the loaf and spreads butter on it. Physical No change in substances. No unexpected color change, temperature change or gas given off. 2. Your friend decides to toast a piece of bread, but leaves it in the toaster too long. The bread is black and the kitchen if full of smoke. 3. You forgot to dry the bread knife when you washed it and reddish brown spots appeared on it. The bread is burned- Color change to black and smoke released- odor change Chemical The knife changed colors- rust Chemical

Physical or Chemical Change?   Scenario Physical or Chemical Change? Evidence… 4. You blow dry your wet hair. 5. In baking biscuits and other quick breads, the baking powder reacts to release carbon dioxide bubbles. The carbon dioxide bubbles cause the dough to rise. 6. You take out your best silver spoons and notice that they are very dull and have some black spots. Did not change your hair- evaporated the water Physical Releasing of gases and changing to another substance batter to bread Chemical The silver is tarnished- similar to rusting (reacted with oxygen) changed colors Chemical

Physical or Chemical Change?   Scenario Physical or Chemical Change? Evidence… 7. A straight piece of wire is coiled to form a spring. 8. Food color is dropped into water to give it color. 9. Chewing food to break it down into smaller particles represents a _________ change, but the changing of starch into sugars by enzymes in the digestive system represents a ___________change. 10. In a fireworks show, the fireworks explode giving off heat and light. Its still the same piece of wire- changed appearance Physical Its still water- just tinted a different color Physical Breaking up food to smaller pieces Physical Changing the food to something else Chemical Heat and light are released –changing energy Chemical