UNIT: Chemistry and Measurement TOPIC: Units and Unit Conversions Objectives: Lesson 3 of 4 You will understand the relationship that exists between mass and volume You will learn which units we use to measure mass, volume, and length You will learn what the Metric System is and the common prefixes used in measurement You will learn how to convert between two units of temperature; degrees Celsius and Kelvin

Quickwrite In 1-2 sentences answer one of the questions below: What are some units of measurement you’re familiar with? In football, the field is measured in yards, is the yard part of the metric system or the English (standards) system??? Analyze gold blocks A and B below, which block do you think has more mass (more atoms)? Which block do you think has a greater volume (takes up more space)? B A = Gold Atom

Mass and Volume Relationship Because Block B contains more atoms or “stuff” it therefore has a greater mass We could verify this by putting both blocks on a scale The block with more mass, Block B contains more atoms and will consequently weigh more Notice, mass is measured in grams Mass is how much stuff or matter an object is made of Think of mass as how many atoms or molecules make up an object For example, consider two gold blocks, Block A and Block B, both of which are naturally made up of gold atoms Which block has more mass, Block A or Block B? A 50 grams = Gold Atom B 90 grams

Mass and Volume Relationship If an object has Mass, it takes up space Volume measures how much space an object takes up It is measured in either milliliters (mL) or centimeters cubed (cm3) Once again, consider our two gold blocks, Blocks A and B Which Block has more Volume? In other words, which block takes up more space? Because Block B has more Mass, it will have a greater volume We could verify this by submerging both Blocks in equal amounts of water Notice, Block B displaced more water, therefore Block B has a greater volume A B = Gold Atom

What is the relationship between Mass and Volume? Mass is a measure of how much stuff or matter an object is made of Mass is measured in grams (g) If an object has Mass, it has Volume Volume is a measure of how space an object takes up Volume is measured in Liters (L) or milliliters (mL)

Metric System 1 meter also contains 100 centimeters (1 meter = 100 centimeters) 1 meter also contains 1000 tiny millimeters (1 meter = 1000 millimeters In science, we use the metric system The metric system is a measurement system based on mulitples or powers of ten Consider a meter stick, which we use to measure length 1 meter contains 10 decimeters (1 meter = 10 decimeters) 1000 millimeters 1 meter 100 centimeters 1 meter 10 decimeters 1 meter 1 meter = 10 decimeters = 100 centimeters = 1000 millimeters

1 meter = 10 decimeters = 100 centimeters = 1000 millimeters Metric System Notice, as each UNIT became 10 times smaller a different prefix (deci-, centi-, or milli-) was put in front of the base unit METER The same is true if Units become larger Each prefix tells us how large or small a Unit is Meter

Metric System A Gram In the metric system, we use the meter(m) to measure length, the gram (g) to measure mass and the liter(L) to measure volume These are the base UNITS of the metric system Prefixes are placed in front of each base unit to indicate the size and scale of each unit (10 times bigger or 10 times smaller) Liter Meter

What is the Metric System? Measurement system based on multiples of 10 The meter(m) is used to measure length, the gram (g) to measure mass and the liter(L) or milliliter (mL) is used to measure volume Each prefix is either tens time larger or ten times smaller than the next Please write down the table for your notes: Prefix Number Kilo- 1000 Hecto- 100 Decka- 10 Base Unit: Meter, Gram, Liter 1 Deci- 0.1 Centi- 0.01 Milli- 0.001

Unit Conversions and Dimensional Analysis Have you calculated your height in Inches or your age in minutes? If so, you have performed unit conversions A unit conversion is a method of changing a measurement from one unit to another Unit conversions are done using dimensional analysis In chemistry, many of the calculations will involve unit conversions and dimensional analysis Dimensional analysis  is a mathematical system using conversion factors to move from one unit of measurement to a different unit of measurement

Steps for Solving Dimensional Analysis Problems Suppose you have a guitar that is 1 meter in length and you want to know the guitars length in millimeters. Through a series of steps, we can solve this problem: 3. Set up the calculation so the units cancel 1. Start with what the problem gives you 1 meter = ??? millimeters 4. Solve the problem 2. What are the conversion factors? 1 meter = 1000 millimeters 1 meter 1000 millimeters

Steps for Solving Dimensional Analysis Problems A year is 365 days long. How many minutes are in 1 year? Through a series of steps, we can solve this problem: 3. Set up the calculation so the units cancel 1. Start with what the problem gives you 4. Solve the problem 2. What are the conversion factors? 365 days = 525,600 minutes 1 day 1 hour 24 hours 60 minutes

What is Dimensional Analysis? A mathematical system using conversion factors to move from one unit of measurement to a different unit of measurement Steps to solve: Start with what you are given What are the conversion factors? Set up the problem so units cancel Solve the problem

Practice: You walked 5 kilometers to school today. How many meters did you walk? 3. Set up the calculation so the units cancel 1. Start with what the problem gives you 4. Solve the problem 2. What are the conversion factors? 5 kilometers = 5000 meters 1000 meters 1 kilometer

Units of Temperature Celsius -273o 0o 273 100o 373 Kelvin When measuring temperature, two units of temperature you will need to become familiar with is the Kelvin and degrees Celsius Scale On the Celsius scale water boils at 100oC and on the Kelvin scale water boils at 373 K As temperature cools, water freezes at 0oC and 273 K The lowest possible temperature, where all molecular motion stops occurs at -273oC and 0 K

Units of Temperature Celsius -273o 0o 273 100o 373 Kelvin To convert bewteen the Units of temperature we will use the following equation: oC + 273 = K For example, lets say we want to 100oC into Kelvin Substituting our value into the equation we get: oC + 273 = K We could verify this by checking our thermometers to the right, notice 100oC matches up and agrees with 373K 100oC 373 K

Practice: Convert 293 K into degrees Celsius using the equation: 293 K oC + 273 = K oC = 293 K - 273 oC = 10oC 293 K Kelvin 293 K ??? oC 10oC

Summary (you can always write your own summary) Explain the relationship between mass and volume in your own words: What do we use to measure mass, volume and length? What do the following metric prefixes represent: centi-, milli-, and kilo- If you are 60 inches tall, how many centimeters tall are you? Conversion factor: Convert 310 Kelvin into degrees Celsius: 2.54 centimeters 1 inch