 # DENSITY. DEFNITION DENSITY: The mass of a substance per unit of volume In simple terms…How much “stuff” is in a certain amount of space Weight/amt of.

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DENSITY

DEFNITION DENSITY: The mass of a substance per unit of volume In simple terms…How much “stuff” is in a certain amount of space Weight/amt of space taken up

Only way to change density is by changing the temperature or pressure

A.Heating an object causes the density to decrease -- atoms expand and become more spread out (less tightly packed) B.Opposite is true for cooling because atoms contract

Pressure A.As pressure increases, the volume decreases-- atoms become more tightly packed causing density to increase B.The opposite is true for decreasing pressure because the atoms are more loosely packed

SUMMARY INCREASE TEMPERATURE, DECREASE DENSITY DECREASE TEMPERATURE, INCREASE DENSITY INCREASE PRESSURE, INCREASE DENSITY DECREASE PRESSURE, DECREASE DENSITY

WATER Water is the standard used to compare the density of objects

Density of water: The density of water when it is most dense is:

Density of water: Water is most dense at _______° C. This is because water _______________ above and below this temperature 4°C 4 expands

THE DENSITY EXCEPTION Usually, solids are the most dense and gases are the least dense (think of Earth layers) When water freezes into ice, the atoms expand become less packed As a result, ice is less dense than water

THIS IS WHY ICE CUBES FLOAT IN WATER!

Density of water: Any material with a density greater than water will Any material with a density less than water will

DENSITY FORMULA On the front page of the ESRT (Earth Science Reference Tables) Density= mass/volume Use a scale for mass Use lxwxh for regular solids Use cylinder and displacement method for irregular solids Units: g/cm 3 for reg. solids; g/mL for irreg. objects

If substance is cut into pieces or more is added to it, nothing happens to the density- the atoms are still packed the same

Example 1: the density of a gallon of water is 1.0 g/mL. the density of a glass of water is also 1.0 g/mL Example 2: a wood block cut in half has the same density as the original wooden block

Phases of Matter & Density- REVIEW During which phase of matter (solid, liquid, or gas) are most materials:

A rock has a mass of 240g and a volume of 12cm³. Showing all formulas and calculations, determine the density of the rock.

The box below has a mass of 120g. Showing all formulas and calculations, determine the density of the box. 2.0 cm 10.0 cm 2.0 cm

Density of water example: If an object has a mass of 25g and a volume of 50mL, will it sink or float in liquid water?

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