Unit 1- Matter and Measurement

Chapter 1 in text bookDay 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 A Student B Student C

Trial 1 1.54 g 1.40 g 1.70g

Trial 2 1.60g 1.68g 1.69g

Trial 3 1.57g 1.45g 1.71 g

Average 1.57g 1.51g 1.70g

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- 5952 – 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.– 0.0028 – 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– 8260. – has 4 sig figs– 0.0837 – has 3 sig figs

Examples

1. 2801.02. 6933. 9504. 0.3695. 0.05706. 48020.7. 62.01400

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

102.4 g and a volume of 50.0 mL.– Add the following measurements and report them

to the appropriate significant figures: 28.0 cm, 23.538 cm, and 25.68 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

329

5 C F

325

9F C

273.15CK

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 121.3 g. Filled with

carbon tetrachloride (density 1.53 g/cm3 ) the container weighs 283.2 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- H20– Oxygen Gas- O2

– 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