OBJECTIVES: By the end of class, students will be able to

Transcription

1 7 th Grade Science Unit: Matter and Periodic Table Lesson: Matter 11 Law of Conservation of Mass Review Name: Date: Monday, December 12, 2016 Homeroom: OBJECTIVES: By the end of class, students will be able to SWBAT review of the Law of Conservation of mass and earn an 80% or higher on their unit test. DO NOW Directions: Answer the questions using complete sentences. 1. What happened when the baking soda was mixed with vinegar in the last part of the lab demonstration? 2. Why didn t the mass change after the chemical reaction? 3. If three atoms of Substance A and four atoms of Substance B are mixed together to form Substance C and nothing else, how many total atoms will be found in Substance C? 4. If fourteen atoms of Substance A and six atoms of Substance B are mixed together to form Substance C and nothing else, how many total atoms will be found in Substance C 1

2 Class Notes: Vocabulary Review Matter Volume Mass Molecules Atom Law of Conservation of Mass 1. Jason was outside mowing grass, he said he destroyed matter. In your Answer Document, use the Law of conservation of mass to describe to Jason how he could not have destroyed matter. In your answer make sure to compare the mass of the mowed and the unmowed grass. 2

3 Physical Properties Chemical Properties Physical Properties Examples: Chemical Properties Examples: 3

4 Guided Practice: We Do Part 1 Erica was inspired by the class demonstration and wanted to observe some physical and chemical changes on her own. Yay! She took about 6g of fruit-punch Kool-Aid powder and observed some of its properties. Some of them that she observed were: looked more pink that red, tasted mostly sour, was organized as a fine crystalline powder, and reacted vigorously with a base, it must be some sort of acid!). Erica then massed a cup at 10g and poured 12g of water into it. 1A) Erica expects a physical change to occur when she mixes the Kool-Aid powder and water. What process will occur and what is happening to the particles? 1B) What will be the total mass of the cup, and mixture of water and Kool-Aid powder? How do you know? 1C) Name one physical property and one chemical property of both the water and the Kool-Aid and put your answer in the chart below: Physical Properties Chemical Properties Water 4

5 Kool-Aid Part 2 Erica mixed her materials and found support for the law of conservation of mass! But her friend Allan was confused about why it was a physical change and not a chemical one. Use your knowledge of physical and chemical properties to help him understand. 2A) Allan first is confused about whether or not physical changes can change the physical properties of the final matter. Erica is ready to explain: The Kool-Aid powder was a light pink and the water was clear. The mixture is red, however. Think of another example of physical changes creating new physical properties of matter. It can be about this scenario, or of another (like heating metal to very high temperatures to melt it OR filling a balloon with air to decrease its density). 2B) Allan also believes that Kool-Aid powder is mostly sugar with some flavoring. Erica looks up some information about sugar and finds this: when sugar is dissolved in water, it cannot react with either an acid or base because it, like water, is neutral. Use the concept of physical or chemical properties to help Erica use this evidence to explain that the Kool-Aid cannot be sugar. 5

6 Independent Practice 1. The law of conservation of mass says, A. Matter can be created but cannot destroyed. B. Mass is anything with matter and volume. C. Mass can only change forms. D. Mass cannot be created or destroyed, it can only change forms. 2. You are a freshman at Cristo Rey. In your chemistry class your teacher asks you to combine a mass of 50 grams of Sodium with an unknown mass of chlorine. You measure your mixture and its mass is 126 grams. Using the law of conservations of mass, what was the mass of the Chlorine your teacher gave you? A. a mass of 302 grams B. a mass of 113 grams C. a mass of 76 grams D. a mass of 63 grams 3. A tightly sealed glass box has a mass of 20,000 grams and contains a 5-gram cube of ice, making the total mass 20,005g. The box with the ice is placed in direct sunlight and left to melt. Which statement best describes the mass of the sealed box after sitting in the sun. A. The mass decreased because the ice melted into a liquid. B. The mass remains the same as the ice melts. C. The mass increases as the gases inside the box absorb energy and expand. D. The mass increases as the water melts into small droplets. 6

7 4. The scientist observes the rust on the sample of iron filings and dries the sample thoroughly. The scientist weighs the entire sample and finds that it has more mass than the original 118 grams. What explains this increase in mass? A. The sample gained mass during drying. B. The sample gained mass during a physical change. C. The sample gained mass during a chemical change. D. The sample gained mass during a change of state. 5. Explain the law of conservation of mass and describe what matter can do. 7