What is Matter?

Objectives

Explain the relationship between matter, atoms, and elements

Distinguish between elements and compounds Describe molecules, and explain how they are

formed Interpret and write some common chemical

formulas Categorize materials as pure substances or

mixtures

What is chemistry and matter?

Chemistry: the scientific study of the composition, structure, and properties of matter and the changes that matter undergoes.

Matter: anything that has mass and takes up space.

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

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

Compound: a substance made of atoms of two or more different elements that are chemically combined.

Earth's elements % proportions

oxygen, 29.5, 30%

iron, 34.6, 34%

calcium, 1.1, 1%

silicon, 15.2, 15%

sulfur, 1.9, 2%

magnesium, 12.7, 13%

nickel, 2.4, 2%

all other elements , 2.6, 3%

Human body element % proportions

oxygen66%

sodium0%

calcium2%

potassium0%

hydrogen10%

phosphorus1%

carbon18%

sulfur0%

nitrogen2%

all other elements1%

Molecule: the smallest unit of a substance that keeps all of the physical and chemical properties of that substance.– A compound is made of two or more

different elements, but a molecule may be of the same elements or different elements.

Remember: some elements occur singly in nature– Ex) Neon

The atoms of other elements combine to form polyatomic molecules – Ex) O2 H2 P4

Molecules can be represented by:– Formula– Physical models

Chemical formula- a combination of chemical symbols and numbers to represent a substance

C16 H10 N2 O2 Indigo

C8 H10 N4 O2 Caffeine

Mixture- a combination of two or more substances that are not chemically combined

Pure substance- a sample of matter, either a single element or a single compound, that has definite chemical and physical properties

*Elements and compounds are pure substances, but mixtures are not

Mixtures can be separated into their components

Heterogeneous mixture- substances aren’t mixed uniformly and are not evenly distributed– Ex) flour in water – a suspension

Homogeneous mixture- components are evenly distributed, mixture is same throughout– Ex) sugar in water

Solids can mix with liquids

Gasoline is a liquid mixture of ~ 100 liquids

Comprised of miscible liquids Miscibility- only miscible liquids that are

combined (ex. Ethylene glycol and water) can dissolve in each other.

They form a solution (a homogeneous liquid mixture)

Liquids can mix with liquids

Immiscible- liquids such as oil and water or toluene and water that are practically insoluable

Instead, they form two layers, with the denser liquid on the bottom.

Gases can mix with liquids

Ex) Lava– The molten rock in some types of volcanoes

contains large quantities of gas. Pumice, a solid foam that occurs naturally on Earth, is a volcanic rock formed by the violent separation of these extremely hot gases from lava.

– As the exploding lava cools, it traps the bas bubbles.

– Some pumice is so soft that it is spongy, and has such a low density that it floats on water

2.2

Objectives– Distinguish between the physical and

chemical properties of matter, and give examples of each

– Perform calculations involving density– Explain how materials are suited for different

uses based on their physical and chemical properties

– Describe characteristic properties

Physical properties

Physical properties identify things by describing matter

Examples: – Color– Shape– Height– Mass – Volume– density

More examples of physical properties:– Melting point (temperature and pressure at

which a solid becomes a liquid)– Boiling point (temperature and pressure at

which a solid becomes a liquid)– Strength– Hardness– Ability to conduct electricity– Magnetism – Heat

A characteristic of any pure substance is that its boiling point and melting point are constant if the pressure remains the same

.substance Melting point

º Celsius

Boling point

º Celsius

C 3550 4827

Au 1063 2970

Fe 1535 2750

Hg -39 357

N -209 -196

O -218 -183

NaCl 801 1413

H2O 0 100

Density= Mass

VolumeDensity depends on the arrangement of

atoms within that sample of matter

Density determines whether an object will float or sink

Densities of some substancesSubstance Chemical

formulaDensity in g/cm3

Air, dry Mixture 0.00129

Brick Mixture 1.9

Gasoline Mixture 0.7

Helium He 0.00018

Ice H20 0.92

Iron Fe 7.86

Lead Pb 11.3

Nitrogen N2 0.00125

Steel Mixture 7.8

Water H20 1.00

The density of a liquid or a solid is affected only slightly by a change in temperature or pressure.

In a gas however, an increase in temperature or a decrease in pressure significantly reduces the density of a gas

Chemical Properties

Chemical property- describes how a substance changes into a new substance either by combining with other elements or by breaking apart into new substances.– Examples:

• Reactivity of element with other compounds (oxygen, acid, water, other)

• Oxidation of Fe creates rust• Flammability (ability to burn)

Changes of matter

Objectives:– Explain physical change, give examples– Explain chemical change, give examples– Compare and contrast physical and

chemical changes– Describe how to detect whether a chemical

change has occurred

A physical change affects one or more physical properties of a substance without changing its identity

Ex) breaking chalk – Getting a hair cut– Dissolving sugar– Melting ice– Sanding wood– Crushing a can– Mixing oil and vinegar

Mixtures can be physically separated because the components are not chemically combined.

Distillation device- can separate components of mixtures that have different boiling points. When heated, the component that boils and evaporates first, separates from the mixture and collects in the receiving tank

Magnets can be used to separate mixtures that have components containing iron.

•Centrifuge- tool used to separate mixtures. It spins a sample of a mixture rapidly until the components of the mixture separate

Changes in the state of matter are physical because they do not change the identity of the substance!!!

Chemical changes

A change that occurs when a substance changes composition by forming one or more new substances.

Ex) soured milk (produces odor)– Effervescent tablets (produce CO2)– (copper pennycopper carbonate)– Oxidation- (iron rust)– Fruits ripening– Food being digested

Chemical changes form new substances that have different properties

Ex) baking a cake

Chemical changes can be detected Clues suggesting that a chemical

change occurred:– Change in odor or color– Fizzing– Foaming– Production of: sound, heat, light, odor

Chemical changes cannot be reversed by physical changes– Ex) you can not unbake a cake

However, some chemical changes can be reversed under the right conditions by other chemical changes.