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.