1 – Matter, Measurements, and Calculations

Matter and Mass

Matter – anything that has mass and occupies space

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Mass – measurement of the amount of matter in an object; independent of the location of an object

Weight

– Measurement of the gravitational force acting on an object

– Depends on the location of an object

Physical properties

– Properties of matter that can be observed or measured without attempting to change the composition of the matter being observed

Chemical Properties

– Properties that matter demonstrates when attempts are made to change the matter into new substances

Classify each of the following changes as physical or chemical:

a. A match is burned

b. Iron is melted

c. Limestone is crushed

d. Limestone is heated, producing lime and carbon dioxide

e. An antacid seltzer tablet is dissolved in water

f. A rubber band is stretched

Changes b, c, and f are physical changes because no composition changes occurred and no new substances were formed

Others are chemical changes because new substances were formed

* Match is burned—combustion gases are given off, and matchstick wood is converted to ashes


* Limestone is heated—lime and carbon dioxide are the new substances
* Seltzer tablet is dissolved in water—the fizzing that results is evidence that at least one new

material (a gas) is produced

Molecules and Atoms

Molecule – smallest particle of a pure substance that has the properties of that substance and is capable of a stable independent existence \n • Limit of physical subdivision for a pure substance

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Atoms – limit of chemical subdivision for matter

Dalton's Atomic Theory

– All matter is made up of tiny particles called atoms

– Substances called elements are made up of identical atoms

– Substances called compounds are combinations of atoms of two or more elements

– Every molecule of a specific compound always contains the same number of atoms of each kind of element found in the compound

– In chemical reactions, atoms are rearranged, separated, or combined, but are never created nor destroyed

Classification of Molecules

– Diatomic molecules: Contain two atoms

– Triatomic molecules: Contain three atoms

– Polyatomic molecules: Contain more than three atoms

– Homoatomic molecules: Contain only one kind of atom

– Heteroatomic molecules: Contain two or more kinds of atoms

Mixture and Pure substance

Mixture – proportions of components may vary; properties vary with composition; can be physically separated into two or more pure substances

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Pure substance – constant composition; fixed set of properties; cannot be physically separated into simpler substances

Homogeneous Matter

– Matter that has the same properties throughout the sample

– Solutions: Homogeneous mixtures of two or more pure substances

– Samples taken from any part of a mixture made up of one spoon of sugar mixed with a glass of water will have the same properties, such as the same taste

Heterogeneous Matter

– Matter with properties that are not the same throughout the sample

– Properties of a sample depend on the location from which the sample was taken

– Example - Skin, juice, seeds, and pulp of a tomato are different

Elements

– Pure substances that are made up of homoatomic molecules or individual atoms of the same kind

– Example - Oxygen gas made up of homoatomic molecules and copper metal made up of individual copper atoms

Compounds

– Pure substances that are made up of heteroatomic molecules or individual atoms of two or more different kinds

– Examples - Pure water is made up of heteroatomic molecules, and table salt is made up of sodium atoms (ions) and chlorine atoms (ions)

When sulfur, an element, is heated in air, it combines with oxygen to form sulfur dioxide. Classify sulfur dioxide as an element or a compound

Because sulfur and oxygen are both elements and they combine to form sulfur dioxide, the molecules of sulfur dioxide must contain atoms of both sulfur and oxygen

• Sulfur dioxide is a compound because its molecules are heteroatomic

Measurements Units

– Consist of a number and an identifying unit

– Examples - Gallons, Celsius, and Fahrenheit

– Based on units agreed on by those making and using the measurements

Metric System

– Decimal system in which larger and smaller units are related by factors of 10

– Basic unit of measurement: Specific unit from which other units for the same quantity are obtained by multiplication or division

– Derived unit of measurement: Unit obtained by multiplication or division of one or more basic units

Calculate the area of a rectangle that has sides of 1.5 and 2.0 m

* Express the answer in units of square meters and square centimeters

Area = (length)(length) \n In terms of meters, area = (1.5 m)(2.0 m) = 3.0 m2

• Note that m2 represents meter squared, or square meters \n In terms of centimeters, area = (150 cm)(200 cm) = 30,000 cm2

• The lengths expressed in centimeters were obtained by remembering that 1 m = 100 cm

A circular petri dish with vertical sides has a radius of 7.50 cm

You want to fill the dish with a liquid medium to a depth of 2.50 cm

• What volume of medium in milliliters and liters will be required?

* Volume of medium required will equal the area of the circular dish (in square centimeters, cm2) multiplied by the liquid depth (in centimeters, cm)
* Note that the unit of this product will be cubic centimeters (cm3)
* Area of a circle is equal to r2 where  = 3.14
* Liquid volume will be:

• V = (3.14)(7.50 cm)2(2.50 cm) = 442 cm3