Chapter 1The Science of Chemistry

Section 1: What is Chemistry?

Section 2: Describing Matter

Section 3: How is Matter Classified?

Section 1.1 – What is Chemistry?

OBJECTIVES:Describe ways in which chemistry is part of your daily life.

Describe the characteristics of three common states of matter.

Describe the reactants and products in a chemical reaction.

Identify the reactants and products in a chemical reaction.

Differentiate between Chemical and Physical changes.

List four observations that suggest a chemical change has occurred.

Working with the Properties and Changes of Matter

• A chemical is any substance that has a definite composition.

• A chemical reaction is the process by which one or more substances change to produce one or more new substances.

Rank Name Formula Uses1 sulfuric acid H2SO4 Production of fertilizer, metal processing,

petroleum refining2 Ethane C2H4 Production of plastics, ripening of fruits3 Propylene C3H6 Production of plastics4 Ammonia NH3 Production of fertilizer, refrigeration5 Chlorine Cl2 Bleaching fabrics, purifying water, disinfectant6 Phosphoric acid

(anhydrous)P2O5 Production of fertilizer, flavoring agent;

rustproofing metals7 Sodium hydroxide NaOH Petroleum refining, production of plastics8 1,2-dichloroethene C2H2Cl2 Solvent, particularly for rubber

Top Eight Chemicals Made in the United States (by Weight)

Physical States of Matter

The states of matter are the physical forms of matter which are solid, liquid, gas, and plasma.

Macroscopic refers to what you can see with the unaided eye.

Microscopic refers to what you would see if you could see individual atoms.

Properties of the Physical States

Solids have a fixed volume and shape that result from the way their particles are arranged.

Liquids have a fixed volume but not a fixed shape.

Gases have neither fixed volume nor shape.

State Volume Shape Bond Particle Motion

Solid Fixed Fixed Strong Slight vibration

Liquid Fixed Takes the shape of the container Moderate Move past one another

Gas Varies Takes the shape of the container Weak Move apart at high

speeds

Changes of Matter

Physical changes are changes in which the identity of a substance doesn’t change.

Changes of state are physical changes.

Chemical changes occur when the identities of substances change and new substances form.

Chemical Changes

mercury(II) oxide mercury + oxygen

Reactants are the substances are the left-hand side of the arrow.

They are used up in the reaction.

Products are the substances are the right-hand side of the arrow.

They are made in the reaction.

Evidence of a Chemical ChangeEvidence that a chemical change may be happening generally

falls into one of the following categories.

the evolution of a gas the formation of a precipitate the release or absorption of energy a color change in the reaction system

Section 1.2 – Describing Matter

OBJECTIVES:Distinguish between different characteristics of matter, including

mass, volume, and weight.Identify and use SI units in measurements and calculations.

Set up conversion factors, and use them in calculations.

Identify and describe physical properties, including density.

Identify chemical properties.

Matter Has Mass and Volume

Matter is anything that has mass and volume.

Volume is the space an object occupies.

Mass is the quantity of matter in an object.

Devices used for measuring mass in a laboratory are called balances.Weight is the force produced by gravity acting on a mass.

Units of Measurement

• When working with numbers, be careful to distinguish between a quantity and its unit.

• Quantity describes something that has magnitude, size, or amount.

• Unit is a quantity adopted as a standard of measurement

Scientist Express Measurements in SI Units

Base units can be too large or too small for some measurements, so the base units may be modified by attaching prefixes.

SI Prefixes

Converting One Unit to Another

A conversion factor is a simple ratio that relates two units that express a measurement of the same quantity

example: You can construct conversion factors between kilograms and grams as follows:

Sample Problem A

Convert 0.851 L to milliliters.

The equality that links the two units is 1000 mL = 1 L. (The prefix milli- represents 1/1000 of a base unit.)

The conversion factor needed must cancel liters and leave milliliters. Thus, liters must be on the bottom of the fraction and milliliters must be on the top.

Derived Units

Many quantities you can measure need units other than the seven basic SI units.

These units are derived by multiplying or dividing the base units.

Speed is distance divided by time.The derived unit of speed is meters per second (m/s).

A rectangle’s area is found by multiplying its length (in meters) by its width (also in meters).

Its unit is square meters (m2).

Volume is another commonly used derived unit.

The volume of a book can be found by multiplying its length, width, and height.

The unit of volume is the cubic meter (m3).

This unit is too large and inconvenient in most labs. Chemists usually use the liter (L).

1L = 1000 mL = 1000 cm3

Worksheet – 1.2A

Convert the following (SHOW ALL WORK)

1. 253 mL L

2. 1256 cm m

3. 15 g kg

4. 1254 kilocalories calories

5. 5.25 hr seconds

6. 200° C °F

7. 189° F C°

Properties of MatterPhysical Properties

• A physical property of a substance is a characteristic that does not involve a chemical change.

• Physical properties of a substance can be determined without changing the nature of a substance.

• Physical properties include texture, state, melting point, and boiling point.

Density is the Ratio of Mass to Volume

• The density of an object is the mass of the object divided by volume of the object.

• Densities are expressed in derived units such as g/cm3 or g/mL.

• Density is calculated as follows:

The density of a substance is the same no matter what the size of the sample is.

Density Can Be Used to Identify Substances:

Because the density of a substance is the same for all samples, you can use this property to help identify substances

Densities of Various SubstancesHydrogen H2 .0000824

Water H2O .997Aluminum Al 2.699

Iron Fe 7.86Copper Cu 8.94Silver Ag 10.5Gold Au 19.3

Chemical Properties

A chemical property is a property of matter that describes a substance’s ability to participate in chemical reactions.

A chemical property can only be identified by trying to cause a chemical change.

A chemical property of many substances is that they react with oxygen.

example: rusting

Some substances break down into new substances when heated.

Section 1.3 – How Is Matter Classified?

OBJECTIVES:Distinguish between elements and compounds.

Distinguish between pure substances and mixtures.

Classify mixtures as homogeneous or heterogeneous.

Explain the difference between mixtures and compounds.

Atom: The smallest unit of an element that maintains the properties of that element.

Pure Substance:

A sample of matter, either a single element or a single compound, that has definite chemical and physical properties.

There are two(2) types of pure substances: elements, compounds

Element: A substance that cannot be separated or broken down into simpler substances by chemical means.

All atoms of an element have the same atomic number.

Elements are pure substances that contain only one kind of atom.

Ex. Copper and Bromine are elementsEach has its own unique set of physical and chemical properties and is represented by a distinct chemical symbol

Some elements exist as single atoms while some exist as molecules.Monatomic: Elements that exist as single atoms

Molecules: 2 or more atoms combined in a definite ratio.If an element consists of molecules, those molecules contain just one type of atom.

Element name Chemical symbol

Origin of symbol

Hydrogen H First letter of element name

Helium He First two letters of element name

Magnesium Mg First and third letters of element name

Tin Sn From stannum, latin word meaning “tin”

Gold Au From aurum, the latin word meaning “gold”

Tungston W From Wolfrum, the german word for “tungsten”

Ex. Nitrogen is an example of a molecular element because it exists as two(2) nitrogen atoms joined together.

Diatomic: Elements that exist as double atomsNitrogen is a diatomic element. Other diatomic elements are:Nirtogen (N2)Oxygen (O2)Hydrogen (H2)Flourine (F2)Chlorine (Cl2)Bromine (Br2)Iodine (I2)

Some elements exist in more than one formEx. Oxygen gas O2

A molecule where 2 oxygen atoms bond together

Ozone gas O3

A molecule where 3 oxygen atoms bond together

Compound: A substance made up of atoms of two or more different elements joined by chemical bonds.Compounds can be broken down into its individual elements although it can sometimes be a difficult task.

• Compounds can be represented by an abbreviation or formula. • A formula has subscripts which represent the ratio of different atoms in the

compound.• example: H2O has 2 hydrogen atoms and one

oxygen atom • Chemical formulas give information only about what makes up a compound.

• example: the chemical formula for aspirin is

C9H8O4

A structural formula shows how the atoms are connected

This two-dimensional model does not show the molecule’s true shape.

A ball-and-stick model shows the distances between atoms and the angles between them in three dimensions.

A space-filling model attempts to represent the actual sizes of the atoms and not just their relative positions.

A hand-held model can provide more information than models shown on the flat surface of the page.

Mixtures: A combination of two or more substances that are not chemically combined.Ex. Air is a mixture

Air consists mostly of oxygen and hydrogen whose proportions can varyWater is NOT a mixture

Water consists of oxygen and hydrogen whose proportions are exactly the same in every sample of water.In addition, the hydrogen and the oxygen are chemically combined not physically.

• The proportion of the materials in a mixture can change. • The properties of the mixture may vary.• An alloy is a solid mixture.

• example: An alloy of gold and other metal atoms is stronger than pure gold.• 18-karat gold contains 18 grams of gold per

24 grams of alloy.• 14-karat gold contains 14 grams of gold per

24 grams of alloy.

Homogeneous Mixture: The pure substances are distributed uniformly throughout the mixture.

Heterogeneous Mixture: The substances are not evenly mixed.

• Any two samples of a heterogeneous mixture will have the different proportions of ingredients.

• Heterogeneous mixtures have different properties throughout.

Examples of MixturesHomogeneous Iced Tea Uniform distribution of components; components cannot

be filtered out and components will not settle out upon

standing.Stainless steel Uniform distribution of components

Maple Syrup Uniform distribution of components; components cannot be filtered out and will not settle out upon standing.

Heterogeneous

Orange Juice Uneven distribution of components; settles out upon standing

Chocolate chip pecan cookie Uneven distribution of components

Granite Uneven distribution of components

Salad Uneven distribution of components and can be easily separated by physical means

Compound vs. Mixture

Compound MixtureChemically joined Physically mixed

Properties may be very different form elements

that makes it up

Properties of mixture reflects properties of substances it contains

Definite proportionComponents can be present in varying

proportions

Classifying Matter

Chapter 1 Assignments

Section 1.1 Pg 9 # 3- 12QUIZ – 1.1

Section 1.2 Worksheet 1.2ASection 1.2 Pg 19 # 1-13

QUIZ – 1.1 -1.2Section 1.3 Pg 28 # 1-8

Chapter Review Pg 31-33 # 1-31TEST – Chapter 1