Chapter One: Introduction to Chemistry

Introduction to Chemistry What is a physical quantity? It is a property that can be measured or quantified. Some examples include: Mass Temperature What is a SI unit? It is a standard unit of measurement defined by the International System of Units in the modern-day form of the metric system. SI unit: International System of Units Measurement of Time SI unit of time: Seconds Written as: s Other units people use to take time are: minutes, hours Equipment used to take time: Digital stopwatch with the accuracy of 0.01s Analog stopwatch with the accuracy of 0.1s Measurement of Temperature SI unit: Kelvin Written as: K Other units that is used to take temperature: degrees Celsius (°C), Fahrenheit (°F) Equipment used to take temperature: Digital thermometer Alcohol thermometer Data logger Infrared thermometer with the range about -50°C to 1100°C Measurement of length SI unit of length: metre Written as: m Other units people use to measure length: millimeter (mm), centimeter (cm), decimeter (dm), kilometer (km) Equipment used to measure length: * Measuring tape with an accuracy of ± 0.1 cm since it comes in different forms and lengths * Meter rule with an accuracy of ± 0.1 cm Measurement of mass SI unit of mass: kilogram Written as: kg Other units people use to weigh mass: gram (g), milligram (mg), tonne (t), kilotonne (kt) Equipment used to weigh mass: Electronic balance with an accuracy of ± 0.01 g Measurement of volume SI unit of volume: cubic metre Written as: m³ Equipment used to measure volume: * Volumetric flask that measures accurate, fixed volumes like 100 cm³ or 250 cm³ * Pipette that measures accurate, fixed volumes that are larger like 100 cm³ or 250 cm³ * Measuring cylinder that measures a range of volumes to the nearest 0.5 cm³ like 31.5 cm³ and 23.0 cm³ * Burette that measures a range of volumes to the nearest 0.05 cm³ like 41.55 cm³ and 23.00 cm³ Reading the volume of liquid When reading the volume of a liquid, the eyes are positioned at the meniscus which is the curve formed in the surface of a liquid in a container. This is done to avoid parallax error. Types of meniscus There is an upward (concave) which is marked A and downward (convex), which is marked B. Measuring the Volume of Gas Equipment used: Gas syringe gas syringe Methods of Gas Collection These methods collect large volumes. 1) Water Displacement Conditions: The gas has to be insoluble or slightly insoluble in water. Examples of gases: Hydrogen (H₂), Oxygen (O₂), Carbon dioxide (CO₂) water displacement method for gas collection 2) Downward Delivery Conditions: The gas has to be soluble or insoluble and denser than air. Examples of gases: Chlorine (Cl₂), Hydrogen chloride (HCl), Sulfur dioxide (SO₂) downward delivery method for gas collection 3) Upward Delivery Conditions: Gas can be soluble or insoluble and is less dense than air. Examples of gases: Ammonia (NH₃) upward delivery method for gas collection Part Three: Separating Mixtures Separating Mixtures: Magnet Using magnetic attraction. It can be used to separate a magnetic material from a mixture that consists of a magnetic and a non-magnetic material in the mixture. It is separated by using a magnet. Sieving It is used to separate the big lumps and the small lumps of a solid. Only the small lumps go through. A sieve is used to separate the different particle sizes. sieve separating different sized particles