Have you ever wondered how a vending machine "knows" that you have put in the correct amount of change to purchase a snack or a drink? These machines use coin detectors that determine the mass and the size of the coins deposited. In other words, they analyze the density of the coins. United States coinage is minted within very narrow specifications, so the density of each type of coin is always the same. The coin detectors compare the coins inserted to the preset standards to determine if the correct combination of coins has been deposited. In this lesson, you too will determine the density of various coins. OBJECTIVES Recognize the characteristics of density. Design and carry out a scientific investigation. Present your findings in a scientific report. Online Lab This animation will allow you to find the density of a penny, a nickel, and a quarter. Make a hypothesis in which you suggest which coin will have the highest density and which will have the lowest density. A model hypothesis might be: "If the (fill in the name of a coin) has a greater density than the and , then it will have a greater mass to volume ratio. If the (fill in the name of a coin) has a lower density than the and , then it will have a lower mass to volume ratio. Remember to record your data and observations in the data sheet so that you can use them to present your findings. SHOW TRANSCRIPT Present Your Findings Write a one or two summary paragraph discussing this experiment and the results. Use the following questions and topics to help guide the content of your paragraph. According to your data, was your hypothesis correct? (Be sure to refer to your data when answering this question.) Summarize any difficulties or problems you had in performing the experiment that might have affected the results. Describe how you might change the procedure to avoid these problems. List at least two real world examples that apply the findings of this experiment. (Hint: An example of this type was given in the introduction to this project.) What would you like to do next?