an introduction to chemistry, lab skills, and measurement unit 1

An Introduction to Chemistry, Lab Skills, and Measurement

Unit 1

The Scientific Method is loosely defined as the way in which a scientist goes about solving a problem.

Define a Problem

Evaluate the Problem

Devise a Testable Hypothesis

Collect Observations about the Problem

Create an Experiment to test the Hypothesis

Make Observations during the Experiment

Draw conclusions that reflect back to the hypothesis

Form a theory to explain the problem

Share this theory with the Scientific Community through Peer Review Peers

repeatedly test your theory

If they do not agree

If they do agree

A law is a concise statement of a relationship between phenomena that is always the same under the same conditions.

A hypothesis is a tentative explanation for a set of observations

tested modified

1. Matter is anything that occupies space and has mass.

2. A substance is a form of matter that has a definite composition and distinct properties.

Chemistry is the study of matter and the changes it undergoes, as well as the study of chemical energy and its transfer

water, ammonia, sucrose, gold, oxygen

A mixture is a combination of two or more substances in which the substances retain their distinct identities.

1. Homogenous mixture – composition of the mixture is the same throughout.

2. Heterogeneous mixture – composition is not uniform throughout.

soft drink, milk, solder

cement, iron filings in sand

Physical means can be used to separate a mixture into its pure components.

magnetdistillation

An element is a substance that cannot be separated into simpler substances by chemical means.

• 116 elements have been identified

• 82 elements occur naturally on Earth

gold, aluminum, lead, oxygen, carbon

• 34 elements have been created by scientists

technetium, americium, seaborgium

A compound is a substance composed of atoms of two or more elements chemically united in fixed proportions.

Compounds can only be separated into their pure components (elements) by chemical means.

Water (H2O) Glucose (C6H12O6)

Ammonia (NH3)

• If homogeneous matter can be separated by physical means, then the matter is a mixture.

Separating Homogenous Mixtures

Separation of Mixtures

Separating Homogenous Mixtures

• If homogeneous matter cannot be separated by physical means, then the matter is a pure substance.

• A pure substance can sometimes be decomposed into something else, the substance is then a compound.

Kinetic Nature of MatterKinetic Nature of MatterKinetic Nature of MatterKinetic Nature of Matter

Matter consists of atoms Matter consists of atoms and molecules in motion.and molecules in motion.

v

Solid Liquid Gas

OTHER STATES OF MATTEROTHER STATES OF MATTEROTHER STATES OF MATTEROTHER STATES OF MATTER

• PLASMAPLASMA — an electrically charged gas; — an electrically charged gas; Example: the sun or any other starExample: the sun or any other star

• BOSE-EINSTEIN CONDENSATEBOSE-EINSTEIN CONDENSATE — a — a condensate that forms near absolute zero condensate that forms near absolute zero that has superconductive properties; that has superconductive properties; Example: supercooled Rb gasExample: supercooled Rb gas

Physical or Chemical?

A physical change does not alter the composition or identity of a substance.

A chemical change alters the composition or identity of the substance(s) involved.

ice meltingsugar dissolving

in water

hydrogen burns in air to form water

An extensive property of a material depends upon how much matter is is being considered.

An intensive property of a material does not depend upon how much matter is is being considered.

• mass

• length

• volume

• density

• temperature

• color

Extensive and Intensive Properties

Matter - anything that occupies space and has mass.

mass – measure of the quantity of matter

SI unit of mass is the kilogram (kg)

1 kg = 1000 g = 1 x 103 g

weight – force that gravity exerts on an object

weight = g x mass

on earth, c = 9.8 m/s2

on moon, c ~ 1.6 m/s2

A 1 kg bar will weigh

9.8 N on earth

1.6 N on the moon

• Powers of ten are used for convenience with smaller or larger units in the SI system.

Units of MeasurementUnits of Measurement

SI Units

Units of MeasurementUnits of Measurement

Volume – SI derived unit for volume is cubic meter (m3)

1 cm3 = (1 x 10-2 m)3 = 1 x 10-6 m3

1 dm3 = (1 x 10-1 m)3 = 1 x 10-3 m3

1 L = 1000 mL = 1000 cm3 = 1 dm3

1 mL = 1 cm3

Density – SI derived unit for density is kg/m3

1 g/cm3 = 1 g/mL = 1000 kg/m3

density = mass

volume d = mV

A piece of platinum metal with a density of 22.0 g/cm3 has a volume of 4.40 cm3. What is its mass?

K = 0C + 273.15

(°F - 32) * 5/9 = (°F - 32) * 5/9 = °C°C