Introduction to Density What is density? Density is a specific property of matter that is related to the mass divided by the volume What is the formula for density? D = _Mass_ Volume D=M V D = Density M = Mass V = Volume M D V Why does a penny sink in water? Pennies are more dense than water, therefore they sink Why does ice float in water? Ice cubes are less dense than water, therefore they float How will an egg float in water? Egg in fresh water – The egg will sink because it is more dense than the fresh water How will an egg float in water? Egg in salt water – The egg will float because it is less dense than the salt water How will an egg float in water? Egg in fresh and salt water – The egg will be suspended in the middle because it is the same density as the water mixture Calculating Density 1 Frank has a paper clip. It has a mass of 9g and a volume of 3cm3. What is its density? 2. Frank also has an eraser. It has a mass of 3g, and a volume of 1cm3. What is its density? 3. Jack has a rock. The rock has a mass of 6g and a volume of 3cm3. What is the density of the rock? 4. Jill has a gel pen. The gel pen has a mass of 8g and a volume of 2cm3. What is the density of the rock? How Do We Calculate Density in 3 Easy Steps? Step 1 – Calculate the mass of your object using the triple-beam balance How Do We Calculate Density in 3 Easy Steps? Step 2 – Calculating the volume of a regular solid Measure the length, width and height and use the volume formula (V= L x W x H) How Do We Calculate Density in 3 Easy Steps? Step 2 – Calculating the volume of an irregular solid Use the graduated cylinder for the water displacement method How Do We Calculate Density in 3 Easy Steps? Step 3 – Use the density formula D = _Mass_ Volume Water Displacement Method Meniscus: The meniscus is the curve in the upper surface of a liquid close to the surface of the container or another object, caused by surface tension Measure here! Water Displacement Method Examine the graduated cylinders. What must the volume of the rock be? Measuring Mass on a TBB What are the two triple beam balances reading? Place these items in order of density from least to greatest E C E C A D B A D B Summary 1. 2. 3. 4. 5. What is density? Is Ice more or less dense than water? Why? Name an item that is more dense than water. Why does an egg float in salt water? How can we calculate the density of common items?