Float or Sink Density Demonstration

Transcription

1 SPI Density Tennessee SPI Objective: Apply an equation to determine the density of an object based on its mass and volume. Check for Understanding Calculate the density of various objects. Essential Question(s) 1) What is density? 2) What is mass, and how do I measure it? 3) What is volume, and how do I measure it? 4) How do I calculate density? 5) How do I multiply and divide with decimals without a calculator?

2 Float or Sink Density Demonstration Which sodas will sink, and which will swim? Why did the regular soda sink and the diet soda float? Which of these other sodas will sink or float? We determined that diet soda will float and regular will sink, but why did some of the regular sodas float this time? Carbonic Acid (the CO 2 mixture in soda that causes the bubbles) is the reason

3 What is density? Density is the amount of matter (mass) you have crammed in a given space (volume) Reminder: mass is how much matter is in an object Reminder: volume is how much space it takes up (size) The density of an object refers to how compact it is. Particles in an object can be very far apart, or very close together. Particles close together (compact) = dense Unit for mass is grams (mg or g or kg) Unit for solid volume is cubic meters (cm 3 or m 3 or km 3 ) Unit for liquid volume is liters (ml or L or kl) Beads in a Container - Ask yourself: How do the beads in the different containers relate to density? Density is increased by putting in more beads

4 Density Example: Here are two objects that are the same size. (1) Bowling Ball and (2) Soccer Ball One of these objects contains more matter (mass). With two same-sized objects like this (volume), the object with more mass has greater density than the other object. More Dense Less Dense

5 Density in Liquids Lower density liquids will float on top Higher density liquids with sink downward Example: Oil floats on top of water Designation Substance Density Liquid 01 Water 1.0 g/ml Liquid 02 Liquid Mercury 13.6 g/ml Liquid 03 Turpentine 0.8 g/ml Use the table to identify which liquids would occupy levels A, B, and C according to their density. Level A Turpentine (0.8 g/ml) Level B Level C Water (1.0 g/ml) Mercury (13.6 g/ml)

6 Mass The amount of matter (atoms) in an object Measurement Tool: triple-beam or electronic balance Measured in milligrams, grams, kilograms.

7 Volume The size, or amount of space, that an object occupies. Measured in: cubic centimeters (cm 3 ) cubic meters(m 3 ) Milliliters, liters, kiloliters (ml, L, kl) 1cm 3 = 1 ml

8 Volume Calculating the volume of a regular object. Volume = l x w x h

9 Density In Liquids Lower density liquids float on top of liquids with higher density Higher density liquids will sink below lower density liquids

10 Calculating density- divide the mass by the volume of the object Density Formula M D = V Density = mass divided by volume Density = volume mass Easy way to remember which one you are dividing is The mouse goes in the house (mass is the mouse!) Math Vocab: Dividend is the number being divided. In this case it will be the number for mass. Divisor is a number that divides into another number In this case it will be the number for volume.

11 Units: Write it like this: mass/volume MASS Ex: g/cm 3 or g/ml VOLUME

12 Solve the Density Problem Shown Below Go ahead and use a calculator (for now) Round to the tenths place Calculate the density of an object with a mass of 25g and a volume of 10cm 3 What is the formula? Units g/cm 3 D = M V 25 g 10 cm 3 = 2.5 g/cm 3 Don't Forget Your Units! Example: grams/centimeter cubed Written like this g/cm 3

13 Solve with your table: Which cube below has the GREATEST density? Again go ahead and use a calculator (for now). Round to the tenths place. (A) Mass: 12g Volume: 3cm 3 (B) Mass: 19g Volume: 7cm 3 4 g/cm g/cm 3 (C) Mass: 11g Volume: 3cm 3 (D) Mass: 23g Volume: 5cm g/cm g/cm 3

14 Note: The density formula can be rearranged to find the mass or volume. D = M V Mass = Volume x Density (M = V x D) Volume = Density divides Mass Memory Trick: DMV to MVD to VDM V= A) Start with D=MV for density B) Move the first letter (D) to the end C) Now you have M=VD for mass (think M for multiply!) D) Move the first letter (M) to the end E) Now you have V=DM for volume or M D

15 How do you find the density of an irregular shaped object? The formula is still the same M D = V 1. You need to find the mass of the object. How would you do this? The same way that you would find the mass of a regular shaped object (place it on a triple beam balance or an electronic balance) 2. Now you need to find the volume. How are you going to do this? Use the water displacement method. (What is this and how do you do it) 3. Now, solve it. The formula is the same for as regular solids D = M V

16 How do you find the density of a liquid? First, you will need to find the mass of the liquid. How would you do this? 1. What do you do first? Measure the EMPTY container 2. What comes next? Add the liquid to the container and then measure the mass of both the liquid and the container. 3. What should you do now? Subtract the mass of only the container from the total mass (Liquid + Container) (total mass mass of the container ) Next, you need to find the volume of the liquid. How would you do this? Measure the liquid in a graduated cylinder, etc. Now, solve it. The formula is the same for liquids and solids D = M V