Unit 1- Matter and Measurement Chapter 1 in text book Day 1

Qualitative and Quantitative Data Qualitative- information that describes Qualitative Quality 5 senses Ex- color, texture, smell, taste, sound, etc. Quantitative- numerical information Quantitative Quantity Measured Ex- mass, speed, height, length, etc.

Accuracy and Precision Accuracy – How close a number is to the correct answer or value On a test, you need to be accurate to get the question correct. Precision – Having data values that are close to each other If you mass a block three times and your values are 5.67g, 5.66g, and 5.69g; your data is precise.

For each dart board, do the darts have high or low accuracy and precision?

Lets look at some example data! You measure the length of a piece of wood three times and record the following data: 76.48cm, 76.47cm, and 76.59cm. 1.Is your data precise? 2.If the label on the wood says it is 76.49cm long, are your measurements accurate?

Student AStudent BStudent C Trial g1.40 g1.70g Trial 21.60g1.68g1.69g Trial 31.57g1.45g1.71 g Average1.57g1.51g1.70g

Uncertain Digit All measurements are uncertain to some degree – Basis for significant figures The uncertain digit is the guessed digit

Significant Figures (sig figs) Meaningful digits in a MEASUREMENT – The certain numbers and the first uncertain digit. Exact numbers are counted, have unlimited significant figures If the number is measured or estimated, it has sig figs.

Rules for SIG FIGS 1.All non-zero numbers are significant. – Example – has 4 sig figs 2.All zeros between non-zero numbers are significant. – 405 – has 3 sig figs 3.All zeros to the left of the number are not significant. – – has 2 sig figs 4.Zeros on the right of the number are only significant if there is a decimal point. – 1590 – has 3 sig figs – – has 4 sig figs – – has 3 sig figs

Examples

Doing the math Multiplication and division, same number of sig figs in answer as the least in the problem Addition and subtraction, same number of decimal places in answer as least in problem. Example- – Calculate the density of an object that has a mass of g and a volume of 50.0 mL. – Add the following measurements and report them to the appropriate significant figures: 28.0 cm, cm, and cm

Dimensional Analysis Use conversion factors to change the units Conversion factors = 1 1 foot = 12 inches (equivalence statement) 12 in = 1 = 1 ft. 1 ft. 12 in 2 conversion factors multiply by the one that will give you the correct units in your answer.

Temperature A measure of the average kinetic energy Different temperature scales, all are talking about the same height of mercury. Derive a equation for converting ºF toºC

Temperature Conversions

Density Ratio of mass to volume D = m/V Useful for identifying a compound Useful for predicting weight An intrinsic property- does not depend on how much of the material there is

Density Problem An empty container weighs g. Filled with carbon tetrachloride (density 1.53 g/cm 3 ) the container weighs g. What is the volume of the container?

Day 2: Matter

What is matter? Anything that has mass and takes up space. – (Has mass and volume)

Element vs. Compound Element is composed of only atoms from one element – One individual part is an atom Compound is two or more atoms bonded together – Water- H 2 0 – Oxygen Gas- O 2 – One individual part is a molecule

Pure Substance Matter that doesn’t change and is uniform Usually an element or compound – Water – Salt – Carbon Not a pure substance – Salt water – Hot chocolate – Trail mix

Mixtures Homogeneous – Appears the same throughout – A.k.a. a solution Example- lemonade, salt water Heterogeneous – the different parts can be seen Example- Chocolate chip cookie, salad

Mixtures Mixture - combo. of 2 or more pure substances in which each retains its individual chemical props; ex: water & sand. 2 Types: – 1. Heterogeneous - doesn't blend uniformly (water & sand); individual substances remain distinct. – 2. Homogeneous - aka Solutions (soln) - constant composition throughout & always has a single phase. Ex: salt & water : will contain the same relative amounts of salt & water in every drop.

Separating Mixtures Distillation - based on different boiling pts (bpts); mixture is heated until the subst. w/lowest bpt boils to a vapor which can be condensed into a liquid & collected. Crystallization - when a soln has as much solute it can hold, one more pinch will cause the solute to come out of soln & collect as crystals. (Rock candy)

Separation Techniques Filtration- solid part is trapped by filter paper and the liquid part runs through the paper Vaporization- where the liquid portion is evaporated off to leave solid

Separation Techniques Decanting- when liquid is poured off after solid has settled to bottom Centrifuge- machine that spins a sample very quickly so that components with different densities will separate

Separation Techniques Paper Chromatography- used to separate mixtures because different parts move quicker on paper than other