Density and Relative Density

Density and Relative Density CXC

Observation

• Two identical flask are shown one filled with water and the other with kerosene. When measured with an electronic balance the flask filled with water is found heavier than that filled with kerosene. Why?

• The answer is in finding the

  mass per unit volume of 

  kerosene and water 

  in respective flasks.

Density; ρ = m/v

Density is referred to as the mass per unit volume. It is a measure of how tightly packed and how heavy the molecules are in an object.

Density depends on

• mass (usually expressed in grams)

• volume (usually expressed in cm³ or liters)

• 1000cm³ = 1L => 1cm³= 1mL

How to find the density

• Find the mass of object ; m

• Find the volume of object; v

• Divide Density;ρ= m/v

Guided Practice: 1

A block of ice with volume 5.5m³ has a mass of 5060kg.

Find the density of ice.

• Volume of block=5.5m³

  Mass of block= 5060 kg

• Density = mass /volume

                = 5060 kg/5.5m³.

                 = 920 kg/m³.

  The density of ice is 920 kg/m³.

Why does ice floats on water?

Pure water has its highest density 1000 kg/m³_.

_{This explains why ice floats on water.}

Guided Practice:2

A silver cylindrical rod has a length of 0.5m and radius of 0.4m. Find the density of the rod if its mass is 2640kg.

• Mass of cylinder =2640 kg

  Volume of cylinder = πr²h

                                  = 3.14 x 0.4 ² x 0.5

                                  = 0.2512m³

• Density = mass/volume

           = 2640 kg/0.2512m³

               =10509 kg/m³.

Guided Practice:3

A stone has a mass of 112.5g.When the stone is totally immersed in a measuring cylinder containing water the displaced water moves from 50cm³ to 95cm³.Find the density of the stone.

• Mass of the stone =112.5g

  Volume of stone = 95cm³-50cm³=45cm³

• Density = mass/volume

               = 112.5g/45cm³

               = 2.5g/cm³.

Guided Practice:4

Beaker contain 262.5cm³ of a certain liquid weigh 410g,if the mass of an empty dry beaker is 200g. Find the density of the liquid.

• Mass of liquid=410g-200g=210g

  Volume of liquid=262.5cm³.

• Density=mass/volume

              =210g/262.5cm³

              =0.8g/cm³.

Relative Density

• the density of a substance compared to that of water

• density of substance/density of water

• mass of any volume of a substance/ mass of equal volume of water

• it is a dimensionless quantity

• it can never be zero.

Multiple Choice

What is mass?

• A property of matter that is measured in cm³.

• A property of matter that is the amount of atoms and molecules in an object.

• A property of matter that describes how tightly packed an object's atoms are.

• A property of matter that describes how much space something takes up.

Multiple Choice

The tool used to measure the mass of a substance or object is a ______________.

• balance
• graduated cylinder
• ruler
• thermometer

Multiple Choice

What is the first thing you should do when using a triple beam balance?

• Clean the object before placing it on the pan.

• Place the object on the pan and make sure the pointer and zero are align.

• Move the 1's rider to the right.

• Zero out the balance using the adjustment knob.

Multiple Choice

An empty beaker has a mass of 60 grams.  When mercury is added to the beaker, it has a mass of 200 grams. What is the mass of the mercury?

• 140 grams
• 200 grams
• 140 mL
• 260 g

Multiple Choice

A graduated cylinder measures ______________.

• mass

• matter

• water

• volume

Multiple Choice

Which units of measurement are used for volume?

• grams
• centimeters
• grams/milliliter
• milliliter

Multiple Choice

Find the volume of the given figure.

• 308.9 cm³
• 308.2 cm³
• 312.8 cm³
• 302.9 cm³

Multiple Choice

Density _______________

• A property of matter which describes if an object sinks or floats.

• A property of matter which is measured on a triple beam balance.

• A property of matter which describes how tightly packed an object's molecules are.

• A property of matter which is measured with a ruler.

Multiple Choice

What is the formula for density?

• density = mass x volume
• density = mass / volume
• density = mass + volume
• density = mass - volume

Multiple Choice

SI unit of density is

• kgm-⁴

• kgm^-3

• kgm^-2

• kgm

Multiple Choice

True or False:  The density of a specific type of material never changes.  

• True
• False

Multiple Choice

An irregularly shaped piece of gold was lowered into a graduated cylinder holding a volume of water equal to 17 ml. The height of the water rose to 20 ml. If the mass of the gold was 27 g, what was its density?

• 9 g/mL
• 10.5 g/mL
• 6.5 g/mL
• 8 g/mL

Multiple Choice

Calculate the density of the cube.

• 2 g/cm³
• 4 g/cm³
• 6 g/cm³
• 8 g/cm³

Multiple Choice

Find the volume if a substance has a density of 19.3g/cm³ and a mass of 10g.

• .52cm³

• 193cm³

• 1.93cm³

• 29.3cm³

Multiple Choice

A material with a density of 5g/cm³ and a volume of 20cm³ has a mass of

• 25g

• 4g

• 50g

• 100g

Multiple Choice

A material with a density of 5g/cm³ and a volume of 20cm³ has a mass of

• 25g

• 4g

• 50g

• 100g

Multiple Choice

What two types of measurements make up DENSITY? 

• Mass and Volume
• Temperature and Mass
• Grams and Centimeters
• Volume and Weight

Multiple Choice

Jack has a rock. The rock has a mass of 14g and a volume of 2cm³. What is the density of the rock?

• 7 mL
• 7 g/cm³
• 28 g/cm³
• 1/7 g/cm³

Multiple Choice

Which object has the greatest density?

• Box with blue particles

• Box with red particles

• The density of both boxes are equal

Multiple Choice

What is the unit for Density?

• Grams (g)

• Milliliters (mL)

• Grams/Milliliter (g/mL)

Multiple Choice

The physical property relating the amount of matter in a substance to the volume of the substance.

• classify

• density

• volume

• mass

Multiple Choice

The comparison of the density of one material as it relates to another; frequently the comparison is to the density of water.

• relative density

• density

• physical property

• substance

Multiple Choice

A liquid has a density of 626 kg/m³. Work out its relative density.

• 0.844

• 0.721

• 0.586

• 0.626

Relative Density

• the density of a substance compared to that of water

• density of substance/density of water

Relative Density

​

• mass of any volume of a substance/ mass of equal volume of water

Relative Density

• it is a dimensionless quantity

• it can never be zero.

Multiple Choice

If you poured 3 liquids that do not mix how could you tell which one is the most dense?

• The liquid on top
• The liquid in the middle
• The liquid at the bottom

Relative Density

• the density of a substance compared to that of water

• density of substance/density of water

• mass of any volume of a substance/ mass of equal volume of water

• it is a dimensionless quantity

• it can never be zero.