Bellringer

1. What are some physical properties of the beaker of rubbing alcohol in front of you? What makes these physical properties?

2. Watch the demonstration at the front of the class. What are some chemical prop.s of rubbing alcohol? Why is this a chemical property?

Mystery Liquid Activity

Take out your mystery liquid activity from yesterday. We will now finish trading observations and drawing conclusions.

The 3 liquids were Sodium Bicarbonate (baking soda), acetic acid (vinegar), and potassium aluminum sulfate (alum powder)

Density

Which floats, Coke or diet Coke?

Take one minute in your notes to write your prediction and reasoning

Definition of Density

Density: the amount of matter per unit of volume of an object

But what does that really mean?

Compare Thing 1 and Thing 2

Thing 1 Thing 2

Which of these has more matter? Which has more space?So which one is the most dense?

Compare Thing 1 and Thing 2

Thing 1 Thing 2

Matter/

Matter/ Space SpaceLess

dense

More dense

Definition of Density

Density: the amount of matter per unit of space of an object

But what does that really mean?

How compact or packed together the matter is in the space of an object.

Compare Thing 3 and Thing 4

Thing 3 Thing 4

Which of these has more matter? Which has more space?So which one is the most dense?

More dense

Less dense

Liquid Layers – Check it out!

Which liquid has the highest density?

Which liquid has the lowest density?

Which liquid has the middle density?

Can you tell the density of something by looking at it?

Definition of Density

Density: the amount of matter per unit of space of an object

Matter: per: Space:

Mass Volume

Formula for Density

D = m = mass

V volumeUnits: g/mL (liquids) or g/cm3 (solids)

Important conversion! 1 mL = 1 cm3 So 1 g/mL = 1 g/cm3

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Example 1

Osmium is a very dense metal. What is its

density if 50.00 g of the metal occupies

a volume of 2.2 cm3?

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Solution

D = mass = 50.00 g = volume2.2 cm3

= 22.727272 g/cm3 = 22.7 g/cm3

Bellringer 8/31/111. Ms. Phalen found unknown sample of

a solid had a mass of 17.19 g, and a volume of 3 cm3. What is the density of the solid?

2. Ms. Phalen, who is secretly a top secret agent, suspected someone put arsenic, a deadly chemical, in her salad during lunch. Ms. Phalen knew the density of arsenic was 5.73 g/mL. Based on your data from #1, were Ms. Phalen’s suspicions correct? Why?

Which floats, Coke diet Coke or both?

Take one minute to write down your prediction and reasoning beneath your bellringer

Apply it to real life:

More sugar Less sugar

What makes Coke different from diet Coke?

So what can we conclude about density?

More dense = sink Less dense = float

Revisit your prediction and explain (using density) why you were correct or incorrect

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Example 2

What is the density of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL?

33 mL

25 mL

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Solution

Volume (mL) of water displaced = 33 mL - 25 mL = 8 mL

D = mass = 48 g = volume 8 mL

= 6 g/mL

Density Equation

The density equation can be changed using algebra to solve for mass and volume.

m = d x vV = m/d

Whiteboards

Work only with your partnerKeep discussion science basedDon’t let other groups see your answer!

1. If the mass of a metal is 125 grams and its volume is 5 cm3, what is the density of the metal?

Answer: 25 g/cm3

2. Based on the picture, rank the liquids in order of increasing density (leastmost)

(dark is syrup, yellow is oil,

clear is water)

Answer:

(least) Oil, water, syrup (most)

3. If the mass of a liquid is 5.2 grams and its volume is 10.4 mL, what is the density of the liquid?

Answer: 0.5 g/mL

4. The mass of a piece of wood is 14.0 grams, and its volume is 17.5 cm3. What is the density of this piece of wood?

Will the wood sink or float in water? (density of water = 1.0 g/mL)

D = 0.8 g/cm3, the wood will float in water.

5. A rectangular sample of aluminum has a mass of 9.45 grams. It has a length of 2 cm, a width of 1.75 cm, and a height of 1 cm. (remember volume = l x w x h). What is the density of aluminum?

5. 2.7 g/cm3

6. The density of iron is 7.86 g/cm3. We have an iron sample with a volume of 3 cm3. What is its mass?

6. 23.6 grams

7. If the density of aluminum is 2.7 g/cm3 and we have an aluminum sample with a mass of 16.2 grams. Find the volume of the sample

V = 16.2g/2.7 g/cm3 = 6 cm3