9-18-14 Aim: What is Density?

Do Now: What is the difference between mass, weight, and volume?

HW – R&H pp.5-6, A&E #10-18

Definitions

• Mass- the amount of matter or the # of molecules in an object, cannot change, must be weighed to measure (grams).

• Weight- the gravitational pull on an object, can change depending on where you are

• Volume- the amount of space an object occupies. As temp. increases volume increases and as pressure increases volume decreases. Measure by water displacement (graduated cylinder), or lxwxh.

• Density- the concentration of matter in an object or how many molecules are squeezed into how much space.

Density = Mass/Volume grams/cm3

The density of a substance will always stay the same no matter the size or shape of the substance

The only way to change the density of a substance is by applying heat or pressure. However, if you change the density of a substance you have also changed what that substance is.

How to affect Density

• Heat- if a substance is heated it makes the molecules move faster causing the substance to expand, therefore, decreasing its density.

• Pressure- if pressure is put on a substance the molecules will be forced closer together, therefore increasing its density.

• *If you do change the density with heat or pressure than you have also changed what the substance is.

Phases of Matter and Density

• Most substances are densest when they are their coolest and in their solid form.

• Water is the one exception. It is actually densest as a liquid of 4 deg. Celsius.

• All substances will layer out by density with the most dense always going to the bottom and the least dense to the top.

Density and Floatation

• Water has a density of 1 g/cm3 at 4 deg.c.• If an object has a density greater than 1 it will

sink.• If an object has a density less than 1 it will

float.• If an object has a density = 1 it will suspend in

the middle of the water.

9/19/14Aim: How do we calculate Density?

• Do Now:1. A thumb tack is more dense than the human

body, how is this possible?2. How can you change mass, volume, density?3. Calculate the density of a 3cm cube that

weighs 50 grams.

HW: Track storms, Finish Lab

9/22/14Aim: What is a pollutant?

• Do Now- R&H pp. 11-12.• 1. What is a natural resource?• 2. What is an environmental pollutant?

• HW- Finish lab, A&E p.12, #29-39, Study all of Topic 1 for Quiz tomorrow.

Resources

• Renewable Resource- a resource that will regenerate itself in the span of a human life.

• Reusable Resource- a resource that can be used multiple times without having to discard it.

• Recyclable Resource- a resource that can be reformed for a different use.