All About
measuring matters mass volume density
Volume is the amount of space an object takes up. volume The base unit of volume in the metric system in the liter and is represented by L or l. Metric Units 1 liter (L) = 1000 milliliters (ml) 1 milliliter (ml) = 1 cm 3 (or cc) = 1 gram* Which is larger? A. 1 liter or 1500 milliliters B. 200 milliliters or 1.2 liters C. 12 cm 3 or 1.2 milliliters*
Measuring Volume We will be using graduated cylinders to find the volume of liquids and other objects. Read the measurement based on the bottom of the meniscus or curve. When using a real cylinder, make sure you are eye-level with the level of the water. What is the volume of water in the cylinder? ml What causes the meniscus? A concave meniscus occurs when the molecules of the liquid attract those of the container. The glass attracts the water on the sides.
Images created at http://www.standards.dfes.gov.uk/primaryframework/downloads/swf/measuring_cylinder.swf Measuring Liquid Volume What is the volume of water in each cylinder? Pay attention to the scales for each cylinder.
10 cm Measuring Solid Volume 8 cm 9 cm We can measure the volume of irregular object using water displacement. Amount of H 2 O with object = 260 ml About of H 2 O without object = 200 ml We can measure the volume of regular object using the formula length x width x height. Difference = Volume = 60 ml 10 cm X 8 cm X 9 cm = 720 cm 3
Mass refers to the amount of matter in an object. The base unit of mass in the metric system in the kilogram and is represented by kg. Metric Units 1 Kilogram (km) = 1000 Grams (g) 1 Gram (g) = 1000 Milligrams (mg) Which is larger? A. 1 kilogram or 1500 grams B. 1200 milligrams or 1 gram C. 12 milligrams or 12 kilograms D. 4 kilograms or 4500 grams
Measuring Mass We will be using triple-beam balances to find mass. Once you have balanced the scale, you add up the amounts on each beam to find the total mass. What would be the mass of the object measured in the picture? 300g + 70g + 3.32g = 373.32g
PRECISION & ACCURACY
Accuracy We talk about accuracy when the question we ask is: How close is the experimentally measured value to the accepted value?
Precision We talk about precision when the question we ask is: How close is the experimentally measured value to the other experimentally measured values?
Why is this confusing? Precise, is often used non-scientifically to mean exact (which sounds a lot like accurate!)
Matt John Dan Pete Assuming the center bull's-eye is our accepted value: Who is the most accurate at throwing darts? Who is the least precise? Describe John s precision and accuracy to the other dart throwers. example: Pete s darts are less accurate and less precise than Matt s, less accurate and more precise than John s, and more accurate and more precise than Dan s.
example: Three students weigh a sample of known weight (4.50 g), four times each Donovan: 4.56 g, 4.55 g, 4.76 g, 4.58 g» Average = 4.6125 g» Range 0.21 Mike: 4.55 g, 4.56 g, 4.66 g, 4.53 g» Average = 4.575 g» Range 0.13 Kevin: 4.77 g, 4.78 g, 4.76 g, 4.79 g» Average = 4.775 g» Range 0.03 Who is the most accurate? Mike is 0.08 g off, Donovan is 0.11 off, and Kevin is off by 0.28 g Mike is the most accurate because he is the closest to the true value Who is the least precise? Donovan has the highest standard deviation and the largest range, therefore he is the least precise.
How Precise are your Measurements?
A distinguishing property DENSITY
Density is a measure of how mass and volume are related in an object. An object s density is the amount of matter it has in a given space. To find density: first measure mass (m) and volume (v) then use this formula
Density is an important physical property of an object. mythbusters sulfer hexofluoride sulfur hex2 1. The density of a substance is always the same (at a given T and p)
2. The density of one substance is always different than the density of another substance.
Density math challenge mass: 96.6 g volume: 5.0 cm 3 You went panning for gold and found a nice nugget. How do you know if it s real or just fool s gold? Remember D = m/v Density of gold 19.32 g/cm 3 Density of fools gold (iron pyrite) 5.02 g/cm 3
Let s Try a few Calculations Fun with math in science!
1. A brick of salt with a mass of 433 g measures 10 cm x 10 cm x 2 cm. What is its density? 2.16 g/cm 3 D = m/v m = 433 g v = 10 cm x 10 cm x 2 cm = 200 cm 3 D = 433/200 = 2.16 g/cm 3
5. An ice cube has a density of 0.917 g/ml and measures 5.8 cm x 5.8 cm x 5.8 cm. What is its mass? 178.9 g D = m/v m = Dv v = 5.8 cm x 5.8 cm x 5.8 cm = 195.11 cm 3 m = (0.917 g/ml)(195.11 cm 3 = 178.9 g
6. Gasoline will float on water. 450 g of gasoline is spilled into a puddle of water. If the density of gasoline is 0.665 g/ml, what volume of gas was spilled? 676.7 ml D = m/v v = m/d v = 450 g 0.665 g/ml = 676.7 ml
last one 13. Rocks are sometimes used along coasts to prevent erosion. If a rock needs to weigh 2,000 kg (about 2 tons) in order not to be shifted by waves, how big (volume) does it need to be? You are using basalt which has a typical density of 3200 kg/m 3. v = m/d = 2,000 kg 3,200 kg/m 3 0.625 m 3
DENSITY MINI LAB
Floating and Sinking A study of Density
What Makes something Float or Sink in water? What s the Difference? Using what you know of density and the information that the density of water is 1 g/ ml (or 1 kg/l) provide an explanation about how you could predict if an object will float or sink in water. Floating and sinking
Exploring density: PHET floating and sinking PHET Lab
Atoms, elements, compounds and mixtures A CLOSER LOOK AT MATTER
Which of these is matter? air light water darkness smoke jello heat human cloud cold sound diamond
What is matter? Matter is anything that has mass and takes up space. Matter can be classified by extensive or intensive properties. Extensive properties depend on the amount of matter in the sample. Intensive properties do not depend on the amount but the type of matter in the sample.
Matter is made up of elements Pure substances that cannot be broken down by chemical changes. Each element has unique properties.
Property of almost all elements the ability to combine with other elements and form compounds Combine in fixed ratios. Hydrogen peroxide Glucose C 6 H 12 O 6
Matter is made up of compounds elements combine to form larger particles called compounds.
mixtures compounds CLASSIFICATION OF MATTER
Classification model
Pure Substances A pure substance always has the same composition and the same characteristics/properties (density, color, taste, smell, boiling point) compounds Can be broken down into simpler substances using chemical methods elements Can t be broken down any further. Contain only one type of atom. Approx. 109 elements
mixtures Made up of two or more substances that are not combined chemically so do not create a new substance. They can be separated by mechanical means. Most things in nature are mixtures
Mixtures Mixtures are physical blends of two or more components. Mixtures are classified into two groups: Heterogeneous mixtures are not uniform. Their components are not evenly distributed. Homogeneous mixtures are uniform and their components are evenly distributed.
What kind of mixture is it? heterogeneous Homogeneous Heterogeneous Homogeneous Homogeneous heterogeneous
Classification model
Element, Compound, or Mixture? Rocks
Element, Compound, or Mixture? Copper
Element, Compound, or Mixture? Jelly Beans
Element, Compound, or Mixture? Table Sugar
Element, Compound, or Mixture? Diamond
Element, Compound, or Mixture? Tea
Element, Compound, or Mixture? Salt
Element, Compound, or Mixture? Neon Gas
Element, Compound, or Mixture? Pure Water
Element, Compound, or Mixture? Aluminum
Element, Compound, or Mixture? Lemonade
Element, Compound, or Mixture? Silver
Element, Compound, or Mixture? Sand
Is a Glow Stick Compound or Mixture? Glow sticks give off light when two solutions are mixed. The sticks consist of a small, brittle containers within a flexible outer container. Each container holds a unique solution. When the outer container is flexed, the inner container breaks, allowing the solutions to mix, causing the necessary chemical reaction. After breaking, the tube is shaken to thoroughly mix the two compounds.
Separating mixtures Chromatography of inks
Why use chromatography? remember: chromatography is used to physically separate components in a mixture by passing it in solution across a medium (the paper) in which the different components move at different rates. chromatography can purify basically any soluble or volatile substance if the right adsorbent material, carrier fluid, and operating conditions are employed.
Calculating R f (retention factor) It's a measurement of how the compound is interacting with both the solvent (liquid) and the solid support (paper). basically it is the distance traveled by the compound divided by the distance traveled by the solvent The Rf value tells you how well the solute dissolves in the solvent. The higher it rises on the paper, the better it dissolves in the solvent.
Separating a complex mixture Another engineering challenge!