Topic 5 - Density And review of Topic 4 – Flow Rate and Viscosity

Flow Rate and Viscosity  Viscosity – the property that describes a liquid’s thinness or thickness  A thick liquid is more viscous (not vicious) e.g. molasses, oil, paint, shampoo  A thinner liquid is less viscous e.g. water, pop, alcohol

 Flow rate is the measurement of how long it takes for a fluid to flow a certain distance  Many products require precise measurement of viscosity and flow rate for product formation and application e.g. paints, varnishes, cosmetics, lubricants

Effects of Temperature Liquids  Temperature increase= viscosity decrease  Temperature decrease= viscosity increase Gases  Temperature increase= viscosity increase  Temperature decrease=viscosity decrease

Density  Density can be described as: the “crowdedness” of the particles that make up matter  In scientific terms, density is the mass per unit volume of a substance  So, who cares and what does this mean?

 The particle model tells us that different substances have different-sized particles  The size of the particles determines how many particles can fit into a given space  Therefore, each substance has its own unique density

 Imagine one container with liquid water and another container with water vapour  Both liquid water and water vapour have the particles of the same size  But the particle model tells us that gas particles have more space between them than do liquid particles  Therefore, water vapour will have fewer particles than the liquid water  So water vapour is less dense!!!!!!!

Questions to ponder….  What if gases were more dense than solids or liquids?  What if water was more dense than you?  Can you think of any liquids that may be more dense than solids?

How are mass and volume related?  Mass = the amount of matter in a substance  Volume = the amount of space occupied be a substance How can you measure the volume of a solid, liquid and gas?

IMPORTANT! CRUCIAL! IMPERATIVE! IMPORTANT! CRUCIAL! IMPERATIVE!  Mass is NOT the same thing as Weight  Weight is the force of gravity exerted on an object  A force is a push or a pull or anything that causes a change in the motion of an object (always measured in Newtons (N))  Gravity is the natural force that causes an object to move towards the centre of the Earth (9.8N per kilogram of mass)

The Formula for Density  The density of an object is determined by calculating the mass to volume ratio Density (D) = Mass (m)/Volume (V) OrD=m/V

 The density of solids is usually given in g/cm 3  The density of liquids and gases is usually given in g/L or g/mL e.g. density of Mercury equals g/mL Important to know: 1 gram/cubic centimetre (g/cm 3 ) Equals 1 gram/millilitre (g/mL)