Download Study Guide for Composition of Matter Test - seys

Science 8
Study Guide for Composition of Matter Test (11/18/08)
Marina Chan
11/15/08
Matter and Energy 1.3 - Matter combines to form different substance
Matter can be pure or mixed:
- matter can be
- pure: has only one type of component, such as a single type of atom or a single combination of
atoms that are bonded together
- atom
- molecule
- element: contain a single type of atom:
- pure silver = silver atoms
- pure gold = gold atoms
- compound: single combination of atoms bonded together
- pure water = contains only water molecules
- water molecule = hydrogen and oxygen atoms bonded together as molecules
- mixed: 2 or more substances mixed together physically and can only be separated physically
- air
- drinking water
- most substances you see are mixed
- often the difference between pure and mixed substances is apparent only on the atomic or molecular
level
Atoms, molecules, elements, compounds, mixtures:
pure matter:
- atom: the smallest basic unit of matter
- the smallest unit of an element considered to be that element
- molecule: a particle made when two or more atoms bond together chemically, or combine
- a molecule can be a molecule of an element (two or more of the same atoms)
- the smallest unit of an element considered to be that element
- (all compounds are molecules, but not all molecules are compounds)
- a molecule can be a molecule of a compound (two or more different atoms)
(- the smallest unit of a compound considered to be that compound)
- element (a type of pure substance): a substance that contains only a single type of atom / it can’t
be broken down
- the smallest unit of an element is an atom
- many of the same type of atom
- the number of atoms are not important as long as atoms are the same type
- an element cannot be separated into other substances
- there are as many elements as there are types of atoms = more than 100
- eg.
- silver
- oxygen
- hydrogen
- helium
- aluminum
- compound: a substance that consists of two or more different types of atoms bonded together
chemically
- the smallest unit of a compound is a molecule
- some types of compounds are made of molecules:
- water
- carbon dioxide (dry ice)
- some types of compounds are made of atoms that are bonded together in a different way
- table salt
- compounds can have very different properties from the individual element that make up
the compound
- pure table salt = made up of sodium and chlorine
- table salt is safe to eat
- sodium and chlorine are poisonous
mixed matter:
- mixture: a combination of different substances that remain the same individual
substances and can be separated by physical means
- mixtures do not always contain the same amount of the various substances
- examples:
- seawater
- blood
- plasma
- fruit salad
- heterogeneous mixture (below)
- homogenous mixture (below)
Comparing compounds and mixtures:
1 difference:
- compounds are new substances formed by atoms that bond together (compounds have very
different properties than the elements it is made of)
- the substances in mixtures remain the same substances (mixtures contain several substances
which keep their properties)
2 difference:
- compounds can be separated only by breaking the bonds between atoms
- mixtures can be separated by physical means
3 difference:
- the proportion of different substances in a compound are fixed because the type and number of
atoms that make up a basic unit of the compound are always the same
- the proportion of the different substances in a mixture can vary throughout the mixture or from
mixture to mixture
Parts of mixtures can be the same or different throughout (hetero/homogeneous):
- heterogeneous mixture: a mixture that has different properties in different areas of the mixture
- vegetable soup
- soil
- homogeneous mixture: a mixture whose substances are evenly spread throughout (where one
part of a mixture cannot be told from the other part)
- tea
- homogenized milk
Chemical Interactions 1.1 - Atoms are the smallest form of elements.
Models of atoms: (Dalton) orbits & clouds:
- John Dalton: an early British scientist in the 1800s
proposed:
- each element is made of tiny particles called atoms (but now, it is known that atoms are
make up of smaller particles)
- all of the atoms of a particular atom are identical but are different from atoms of all other
elements
- one of the several people who changed the model of the atom
- electrons in the electron cloud
- move about the nucleus very quickly
- not possible to determine their exact position exactly
- therefore we picture the electrons as a cloud around the nucleus = electron cloud
- remain associated with nucleus
- because attracted to the positively charged protons
- because electrical charges that are alike repel each other = electrons remain
spread out in the electron cloud
Atomic particle: names, location, charge, mass:
- atoms contain charged particles
- charge can either be positive or negative
- particle with same type of charge: repel each other / are pushed apart
- particle with different type of charge = attack each other / are drawn toward each other
- atoms are neutral = have no overall electrical charges because they have an equal number of
protons and electrons
- atoms are composed of three parts:
- protons = a positively charged particle
- grouped with protons in the nucleus of the atom (nucleus = because it contains
protons, the nucleus has a positive charge)
- protons define the element
- neutrons = an uncharged particle (neutral)
- grouped with electrons in the nucleus of the atom
- electrons = a negatively charged particle
- move around outside the nucleus in the electron cloud
- the electron cloud has a negative charge
- Particles changes and mass
Particle
Electron
Proton
Neutron
Relative Mass
Relative Charge
1
-1
2000
+1
2000
0
- mass
- atoms = very small – about 10-10 in diameter
- protons and neutrons
- have about the same mass
- electron cloud = about 10,000 times the diameter of the diameter of the atom
- electrons
- much smaller than protons or neutrons = about 2000 times smaller
Atomic numbers and atomic mass numbers:
-
atomic number: the number of protons in the nucleus of an atom
- the identity of an atom is determined by the number of protons in an atom’s nucleus
- every hydrogen atom = 1 proton in nucleus = atomic number is 1
- every gold atom = 79 protons in nucleus = atomic number is 79
- every atom of a given element has the same atomic number (because the same number of
protons)
- atomic mass number: the total number of protons and neutrons in an atom’s nucleus
- atoms of a certain element
- always have the same number of protons
- may not always have the same number of neutrons = not all atoms of an element
have the same atomic mass number
- chlorine atoms
- 17 atoms
- some have 18 neutrons, some have 20 neutrons
- chlorine atoms with 18 and 20 neutrons = chlorine isotopes
- the atomic mass number between every atom of a given element varies because the
number depends on the number of neutrons (isotopes)
Isotopes: definition, examples, charges:
isotopes = atoms of the same element that have a different number of neutrons
- some elements have many isotopes while some elements have just a few
- chlorine isotopes
- chlorine - 35
- atomic mass number= 35
- 17 protons
- 18 neutrons
- 17 electrons
- chlorine – 37
- atomic mass number = 37
- 17 protons
- 20 neutrons
- 17 electrons
- a particular isotope is designated by the name of the element and the total number of its
protons and neutrons = atomic mass number – atomic number = number of neutrons
- the charge of the whole atom is still neutral because is does not matter how many neutrons
there are in an atom because neutrons have no electrical charge.
Ions: definitions, examples, charges:
ion: formed when an atom loses or gains one or more electrons
- when the number of electrons is different from the number of protons = ions have an overall
electrical charge (as opposed to regular atoms that have no electrical charge because it has an equal
number of electrons and protons)
- formation of positive ions:
- atoms lose one electron (one more proton than electrons) = a positive ion
- smaller than the neutral atom = because since there are fewer electrons, there is less of a
repulsion among the remaining electrons
- sodium atom (Na) becomes a positive ion
- Sodium atom (Na): 11 electrons (11-)
- Sodium ion (Na+): 10 electrons (10-)
- symbol
- represented by symbol for element + raised plus sign (to indicate positive charge)
- Na+
- some atoms form positive ions by losing more than one electron
- symbol:
- calcium loses 2 electrons = Ca2+
- aluminum loses 3 electrons = Al3+
- formation of negative ions:
- atoms gain one electron (one more electron than protons) = negative charge
- larger than the neutral atom = because the extra electron increases the repulsion within
the cloud, causing it to expand
- chlorine atom (Cl) becomes a negative atom
- Chlorine Atom (Cl): 17 electrons (17-)
- Chlorine ion (Cl-): 18 electrons (18-)
- symbol
- represented by a minus sign
- Cl- if gained more than one electron, the number of added electrons is written in front of the minus
sign
- O2- (oxygen gains 2 electrons when it forms an ion)
Other:
- about 100 basic substances or elements that account for everything we see and touch are known today
- Earth’s crust: oxygen is the most common element
- Human body: oxygen is the most common element
- animals, plants and bacteria contain at least 25 types of atoms
- names and symbols of elements:
- first letter of name (capitalized)
- first letter and one other letter in name (first letter is capitalized, second letter is lower case)
- less obvious – come from Latin names
SEPUP Chapters
12: Evaluating Materials: Which is the best material for making a drink container?
- material: is a type of solid matter used to make things
- Each material has particular characteristics, or properties, that make it useful for holding
drinks. Each material is made from specific resources and has a set of effects on the environment when it
is discarded or recycled.
- materials scientist and materials engineer study materials and design new ones
- when they design these materials, some of the things they think about are:
- How will they be used?
- What resources are needed to make them?
- What will happen to them when they are no longer useful?
- evidence: when deciding what material was best to use to make a container, we needed evidence
of the good properties the material had and the bad properties that the other two materials had to show
why we made the decision we made
- material: aluminum, plastic and glass
- properties: the properties of the three different materials were on the cards. We needed to
consider all of the properties of each material when deciding what material to use
- raw materials
- production of waste and pollutants
- recycling ability
- how many containers a ton makes
- (% recycled)
- (the % of the solid waste in the US that they make up)
- (the cost to produce a 12-ounce container)
- trade-offs: when deciding what material would be best to use, we had to make a lot of trade-offs
- trading off lower percentages of solid waste the material makes in the US by weight for
the recycleability of glass, which is better for the environment and saves energy.
- bar graph: bar graphs were used to more easily compare the statistical data of the physical
properties etc. of each material
13: Product Life Cycle: How can a life-cycle diagram be used to make a decision about a product?
- life cycle: all of the stages that a container goes through
- what is needed to make the container, how it will be made, and what will happen to it when it is
no longer being used
- life-cycle diagram: one way of illustrating each stage in the cycle
- show how the inputs and outputs from one stage relate to the inputs and outputs of other stages
- can be used to make decisions that reduce the harm that manufacturing and disposing of a product
might cause to the environment
- raw material: Raw materials come from the earth. They are substances that are used to manufacture a
product. It takes energy of both humans and machinery to gather or mine raw materials for products.
- manufacturing: In the manufacturing stage a product or material is created. Raw materials and energy
are inputs.
- useful life: starts when bottles are filled, labeled and packaged and shipped to stores – and consumer
drinks out of it
- end of life:
- examples:
- reuse to hold things
- put into landfill
- recycled
- Green chemistry (guidelines): guidelines to reduce the negative environmental impact of the products
- It is better to prevent waste than to clean it up after it has been created
- New products should be designed to use inputs and create outputs that are not toxic and
hazardous
- Energy use should be minimized
- Manufacturers should use raw materials that are renewable instead of resources that
cannot be replaced
- Materials should be designed so that after being used, they break down or can be reused
and do not end up in landfills
- the guidelines were used to help us think of ways to reduce the negative environmental impact of
the product
Graphs
- write x and y axis
- x axis = horizontal
- y axis = vertical
- put unit in parentheses after title of each axis
- eg. (kg)
- make space to write materials on x axis
- numbers line up with lines
Vocabulary List
- element: a substance that contains only a single type of atom / it can’t be broken down
- compound: a substance that consists of two or more different types of atoms bonded together /
combined chemically and can only be separated chemically
- mixture: a combination of different substances that remain the same individual substances and can be
separated by physical means
- heterogeneous mixture: a mixture that has different properties in different areas of the mixture
- homogeneous mixture: a mixture whose substances are evenly spread throughout (where one part of a
mixture cannot be told from the other part)
- molecule: a particle made when two or more atoms bond together chemically, or combine
-
proton: a positively charged particle located in the nucleus of the atom (protons define the element)
neutron: an uncharged particle with no electrical charge (neutral) located in the nucleus of the atom
nucleus: the central region of an atom where most of the atom’s mass is found in protons and neutrons
electrons: negatively charged particles that orbit in a cloud outside the nucleus
atomic number: the number of protons in an atom’s nucleus
atomic mass number: the total number of protons and neutrons in an atom’s nucleus
isotopes: atoms of the same element that have a different number of neutrons
negative ion: atoms gain one electron
positive ion: atoms lose one electron
charge: a plus or minus electrical charge that something might have
- evidence: something that serves to prove or disprove a belief or conclusion
- material: is a type of solid matter used to make things
- materials scientist: study materials and design new ones
- materials engineer: study materials and design new ones and use life-cycle diagrams when making
decisions about a product. These diagrams show how the inputs and outputs from
- properties: characteristic qualities or distinctive features of something each material has particular
characteristics, or properties that make it useful for holding drinks
- trade-offs: When you make a decision, it is something that you give up for something that you think is
better
- bar graph: a graph consisting of a series of vertical or horizontal bars representing statistical data
- life cycle: all of the stages that a container goes through together are called the life cycle of a product
- life-cycle diagram: one way of illustrating each stage in the cycle
- raw material: Raw materials come from the earth. They are substances that are used to manufacture a
product. It takes energy of both humans and machinery to gather or mine raw materials for products.
- manufacturing: In the manufacturing stage a product or material is created. Raw materials and energy
are inputs.
- useful life: During its useful life, the product is used for its intended purpose, or, perhaps, an unintended
purpose. (Products that are designed from more durable materials will have a longer useful life, reducing
the overall energy and resources needed to replace them.)
- end of life: When a product is no longer useful, it is in its end-of-life stage. This is when it is thrown
away. There can be several end-of-life options for a product.
- Green chemistry (guidelines): guidelines to reduce the negative environmental impact of the products
(above)