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# Lecture: Density (Mikey’s Lecture)

Lecture: Density (Mikey’s Lecture). 1,2,3 A,B,C Don’t You Know it’s:. DENSITY!!! How do you isolate the circled value?: 1+2=3 : 1+2 -2 =3 -2 1=3-2  1 =1 1+2=3 : 1 -1 +2=3 -1 : 2=3-1 : 2 = 2. A+B=C : A+B -B =C -B : A=C-B A+B=C : A -A +B=C -A

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## Lecture: Density (Mikey’s Lecture)

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1. Lecture: Density(Mikey’s Lecture)

2. 1,2,3 A,B,C Don’t You Know it’s: DENSITY!!! How do you isolate the circled value?: 1+2=3 : 1+2-2=3-2 1=3-2  1 =1 1+2=3 : 1-1+2=3-1 : 2=3-1 : 2 = 2

3. A+B=C : A+B-B=C-B : A=C-B A+B=C : A-A+B=C-A : B=C-A

4. A=C : B : A x B=C x B B11 : A=C x B A=C x B : : 1 x A=C x B x 1 C C : A = B C

5. D=M : V : D x V=M x V 1 V 1 : D x V=M Key point: what you do to one side of the equal sign, you must do to the other side too (that’s what equal means!!)

6. Density is mass per unit volume: per = divide therefore it is a fraction ie: price per pound: \$/lb : miles per gallon: mi/gal So: density is a measure of two variables of the same substance: how much matter there is for the volume of the same stuff

7. Example: Tear a piece of paper in half. Each piece has half the volume and half the mass, but it is still paper with the same density no matter the size: it’s called a characteristic property, like finger prints or DNA sequences

8. 2. Formula for density Density = mass divided by volume D = M V density is a broken heart or density is mountains over valleys: M V or: M D x V

9. 3. Density of pure water (H20) = 1.000g/ml 4. Density is a characteristic property: solids, gasses? 5. unit for density = g/cm3 (key: two units! for same stuff) mass: amount of matter present, its heft: gram is the unit (must be dry, why?) volume is space occupied by matter: solid: cm3is the unit, measured LxWxH; or with water displacement for irregular objects liquid: use a graduated cylinder: mL is the unit remember: 1cm3 = 1mL

10. Greater than 1g/mL H2O (1g/mL) Mass (g) Less than 1g/mL Volume (mL) • Why are the axis labeled this way (hint: formula for slope)? • Where is the line for the Titanic before-after it hits the iceberg? • For the same substance, the density will be the same, no matter how much you have: straight line. • Also, the density will be different for different substances because it is a characteristic property: soda cans, density columns • What is the approximate density: of all gases? :almost all solids? :submarines/hot air balloons?

11. Required format for solving word problems: 4 steps: • K: Know: state what you know: what is the given info • K? unknown: state what you are trying to solve for: the unknown • F: state the formula (s) which are needed for the solution, two types: -base formula -working formula • Show work: apply working formula, show work, cancel units, k-b-c-m, circle answer

12. Examples of word problems: What is the density of a substance with a mass of 15.2g and a volume of 2.7 ml? What is the volume of an unknown rock which has a density of 3.44 g/cm3 and a mass of 0.0039 kg?

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