Science

• Units of measurement

  • Grams
  • Kilograms
  • Newtons
• Kilograms

  A measure of mass
• Force of gravity

  What bathroom scales actually measure
• Equation linking mass with weight


  1. f = ma

  2. w = mg
• Weight is a force caused by gravity
• Mass is a measure of how much stuff is in something
• On Earth, the weight of a 1kg bag of sugar is 10 newtons
• On the Moon, the weight of the same 1kg bag of sugar is less due to lower gravity
• On Jupiter, the weight of the 1kg bag of sugar would be 25 newtons
• Object thrown away from the Earth

  Experiences a force towards the Earth due to gravity
• Acceleration due to gravity

  Denoted as little g, also known as gravitational field strength
• On Earth, acceleration due to gravity is 10 meters per second
• Gravitational field strength (g)

  Also known as the gravitational field strength, it is the force needed to stop an object from falling due to gravity
• Mass


  A measure of the amount of stuff in an object, indicating how difficult it is to get moving or to stop it
• Mass never changes; for example, mass on Earth remains the same on the Moon
• Acceleration due to gravity

  Measured in meters per second per second or in newtons per kilogram, as it is a force exerted on a unit mass
• Finding weight using an equation

  Weight = mass x gravity
• Weight is the force due to gravity and depends on the masses of the two objects attracted
• Weight on Earth is roughly mass times gravity, e.g., 56 kilograms times 10 equals 560 newtons
• On the Moon, gravitational acceleration is 1.6 meters per second per second, resulting in a weight of 89.6 newtons
• Gravitational field strength changes on the surface of different planets due to their sizes and masses
• An apple with a mass of 100 grams requires a force of about one newton to prevent it from falling to Earth
• Isaac Newton got the idea for gravity from observing a falling apple
• Mass always stays the same, but weight can change depending on the gravitational field strength
• Weight can be different on the Moon compared to Earth due to the Moon's lower gravitational field strength
• Common strong acids in the laboratory

  • Hydrochloric acid (HCl)
  • Sulfuric acid (H2SO4)
  • Nitric acid (HNO3)
• Hydrochloric acid


  The most common acid in a lab
• Sulfuric acid


  The most important acid in industry, used for production of agricultural fertilisers, detergents, dyes, paints, plastics, found in car batteries, and has many more uses
• Diluting strong acids in the laboratory

  1. Add acid slowly-slowly, bit by bit in lots of water, never the other way around

  2. Never add water to acid! The heating generated might boil the solution violently causing splattering of concentrated acid
• A good phrase to remember the rule of adding acid to water: "Do not spit in acid"
• Alkali


  A base that is soluble in water
• Alkalis

  • Have bitter taste and feel soapy to the touch
  • Many cleaning products contain alkalis, like bleach, household ammonia, and soap
• Alkalis can react corrosively with other materials and can burn your skin. In the lab, they must be handled carefully and always while wearing appropriate protective clothing, such as lab coats, gloves, and safety glasses
• Neutral substances


  Neither acidic nor alkaline
• We cannot tell if a substance is acidic, alkaline, or neutral just by looking at it. We use indicators to distinguish between the three classes of substances
• What is the force holding ionic compounds together?

  Electrostatic
• Electrostatic attraction between the oppositely charged ions holds them together.
• Ionic bonds are typically stronger than covalent bonds due to the electrostatic attraction between ions.
• What are the typical characteristics of metals?

  Malleable rigid, ductile, dense,
• Common compounds

  Water (H2O), hydrochloric acid (HCl), sulfuric acid (H2SO4), ammonia (NH3), carbon dioxide (CO2), nitric acid (HNO3), and phosphoric acid (H3PO4) are common compounds widely used in industrial and biological applications.