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Properties of Matter. Chapter 2.2. Learning targets for today…. Discuss the differences between physical and chemical properties Calculate densities using the density equation, and see how density applies to things we see everyday Practice using density !
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Properties of Matter Chapter 2.2
Learning targets for today… • Discuss the differences between physical and chemical properties • Calculate densities using the density equation, and see how density applies to things we see everyday • Practice using density! • See a few demos and try to explain what you see!
Physical Properties • White, fluffy, soft, squishy, smelly(?), small, hairy… • These are all physical properties!...ways you can identify something on the surface level • What else could a physical property be? • Let’s jump back to H2O • Describe the physical properties of water • Hint:
So…let’s make a list! • Physical Properties include… • Color • Shape • Mass • Volume • Melting Point (temperature and pressure at which at solid becomes a liquid) • Boiling Point (temperature at which a liquid becomes a gas) • Density!
What is density? • Density = Mass / Volume • Density is the ratio of the mass of a substance to the volume of a substance • What are the units of density?? • Units of mass = ….? • Units of volume = ….? • Volume = length x width x height • Volume = cm x cm x cm = cm³ 1 cm³ = 1mL grams cm³ or mL
Units of Density • Units of mass = ….? grams • Units of volume = ….? cm³ or mL • So, what are the units for density? • Density = Mass/Volume • Units of density = grams/cm³ or grams/mL • How can we manipulate this equation? • If we want to solve for mass, Mass = Density x Volume • If we want to solve for volume, Volume = Mass / Density
A little trick… • Cover up the variable you are solving for… • With the remaining two variables, • Multiply them if they are side by side • Divide them if one is above the other
Let’s practice density • A sample of water has a volume of 10 cm³ and weighs 10 grams. What is its density? • Answer: 1 g/cm³ = density of water • (KNOW THIS!—This will be a test question • Also, it will help you determine what will float and what will sink in water!
Density • How will density relate to what will float and what will sink in water? • Will a blown up balloon float or sink in water? • Float! Why? Because it is less dense than water.
General Rule • Substances that are less dense will rise above substances that are more dense. • If a substance has a density greater than the substance it’s in, it will sink… • Which has a greater density? Oil or water? Less dense—”floats” More dense—”sinks”
Density in the office… • Michael Scott wants to discover the density of his coffee mug. The volume of his coffee mug is 24 cm³ and when he put it on the digital scale, it showed a mass of 48 grams. What is the density of his coffee mug? • Answer: 2 g/cm³ • Will his mug float or sink in water? • Sink!
Let’s look at another… • Pumice is a rock made from cooled lava where gas was dissolved into liquid to form a bubbly material in the solidified state. A piece of pumice is 10 grams and 40 cm³ in volume. What is its density? • Answer: 0.25 g/cm³ • Will this float or sink in water? • Float!
Soda vs. Diet Soda demo…Are all sodas created equal…? • Density Assignment Part 1: On a piece of paper… • Make a hypothesis about what will happen when I put a regular soda and diet soda in a container of water. Will they float or sink?? • Which has a greater density?
Arrange your desks into a circle of 6 desks or so…Density Assignment Part 2: • Your mission, if you choose to accept it, is to decide if an egg will float… • Answer the following and record your data…
Part 2: Egg Floating Experiment • Do you think an egg will float in water? • Based on your prediction before testing, do you think the density of an egg is greater than or less than 1 g/mL? • Actual results: • What could you do to alter the results? • What essentially have you done/manipulated from changing the original floating or sinking conditions?
