Grade 8 Science Notes - Chapter 7 PDF

Grade 8 Science Notes – Chapter 7 Fluid  Anything that flows; a liquid or a gas. Ex: Water, syrup, compressed air in tires. Reviewing States of Matter Solids Liquids Gases Shape Definite...

Grade 8 Science Notes – Chapter 7 Fluid  Anything that flows; a liquid or a gas. Ex: Water, syrup, compressed air in tires. Reviewing States of Matter Solids Liquids Gases Shape Definite Shape Indefinite Shape Indefinite Shape Volume Definite Volume Definite Volume Indefinite Volume Particle Particles Close Particles Close Particles Distant Arrangement Particle Movement Particles Vibrate in Particles Free Particles Move Place Flowing Randomly Change of State Pyramid Gas Solidification Liquid Solid Melting Evaporation  The change from a liquid to a gas Condensation  The change from a gas to a liquid Melting  The change from a solid to a liquid Solidification  The change from a liquid to a solid Sublimation  The change from a solid to a gas Deposition  The change from a gas to a solid The Particle Theory of Matter: 1. All matter is made up of very small particles. 2. All particles in a pure substance are the same. Different substances are made of different particles. 3. There is space between the particles. 4. The particles are always moving. As the particles gain energy, they move faster. 5. The particles in a substance area attracted to one another. The strength of the attractive force depends on the type of particle. Changes of State and the Particle Theory of Matter:  All matter is made of tiny particles (1)  Since there is space between the particles (3) there is room for particles to move.  As the particles gain energy they move faster (4) therefore if we apply heat to particles they will gain energy and move faster. Applying Heat – Causes particles to move faster and change from a solid to a liquid or from a liquid to a gas. Removing Heat – Causes particles to slow down and change from a gas to a liquid or from a liquid to a solid. Viscosity Viscosity  A measure of a liquids resistance to flow. Describes a liquids “thickness” or “thinness”. - The greater the friction between the particles of a substance, the greater the viscosity. Flow Rate  The time it takes for a fluid to flow from one point to another. The formula for calculating flow rate is distance divided by time. FR = D T Viscosity and Flow Rate Viscosity Flow Rate Description High Slow Thick Low Fast Runny Examples of when viscosity is important: 1. Motor Oil  must have a low viscosity in order to lubricate the motor. 2. Paint  must have a higher viscosity in order to cover the surface. 3. Pancake batter  if the batter is too viscous, it will not spread, if it is not viscous enough you will have thin, large pancakes. 4. Food  some foods when kept in the fridge are too viscous (ex: peanut butter) Viscosity and the Particle Theory of Matter Factors affecting Viscosity 1. Temperature  Particles are constantly in motion. As they acquire more energy, they move faster. As liquids are heated the particles move faster and farther apart (4). o As a result, the space between the particles increases and thus the viscosity decreases because there is less friction and the attractive force between the particles is reduced. o Ex: Honey kept in a fridge vs honey heated. 2. Concentration  There is empty space between the particles (3). o Concentration is the amount of substance dissolved in a given volume. If a liquid is concentrated, it means that in general there are more particles in a given space. o Ex: Skim milk, 1% milk, 2% milk, whole milk 3. Strength of attraction between the particles.  There is an attractive force between the particles (5) o The particles of a fluid are attracted to one another but they are also attracted to the object they are flowing over. o Ex: Raindrops on a clothes line. The drops stay together but also stick to the clothes line.