Grade 7 Science Study Guide by HC12091411943


									Grade 7 Science Study Guide
Unit 1 Interactions and Ecosystems
Topic 1- Interactions Within Ecosystems
There is a growing need to understand more about our environment and what impacts that
we have on it.
Ecology: the study of the relationship between living organisms and their environment.
        People who study these relationships are called ecologists.

What all living things need:
-food           -water
-habitat        -air (gas exchange)
Adaptation: Is an inherited characteristic or behavior that helps an organism survive and
reproduce in its environment. Ex. Birds bones are hollow which makes them able to fly.
Ecosystem: the complex set of interactions between living and non-living things in a
particular environment. Ex. A rotting log
Interactions Between Living Things in an Ecosystem
Symbiosis: occurs when two species live closely together in a relationship that lasts over
Three Types:
Mutualism: each partner benefits form the relationship. Ex remora and shark
Parasitism: one partner benefits and the other is harmed. The benefactor is known as the
parasite and the victim is known as the host. Ex tapeworm, mosquito, leech (or you and
your parents. Ha)
Commensalism: one partner benefits and the other appears to be unaffected. Ex. Orchid
plant and tree trunk.
Impacts on Ecosystems
As mentioned, relationships exist between the living and non-living. These can have a
major impact on an environment. Ex. Beaver – water. Beavers (living) build dams to
stop water (non-living) dramatically changing the environment around them.

Topic 2 – Human Impacts on Ecosystems
Human beings also belong to the animal kingdom and happen to have a more dramatic
effect on the Earth’s ecosystems than any other animal.
Natural Resources: The materials or products that are found in nature and are used to
meet our basic needs.
*Know Flow Chart on Gathering Food in Alberta (buffalo – small farm – feedlot)
Needs and Wants
Want: things that make our lives more enjoyable
Needs: The lack of something necessary.
Ex. Food is a need but having food from distant locations year round is a luxury (want).
It is primarily the wants of humans that causes the biggest ecological footprint.

Topic 3 – Environmental Choices
Ecological Footprint: is a calculation of the total area of land and water needed to supply
all of the materials and energy that you use as well as absorb all of the waste you
Sustainability: a term describing a system in which the resources of nature are being
renewed at least as quickly as they are used, and that all wastes are able to be completely
Ways to Help the Environment
The three R’s
Reduce: the amount of garbage you produce
Reuse: reuse products rather than throwing them away
Recycle: find other ways to make use of products if they cannot be reused.

Topic 4 – How Organism Interact
Biotic: living parts of the ecosystem. (plants, animals)
Abiotic: non-living parts of the ecosystem. (Rocks, wind, sun, water)
Niche: the role of an organism in its ecosystem
Producers: make food for themselves using photosynthesis. E.g. plants
Consumers: eat and consume things made by producers, or other consumers. E.g. humans
Herbivores: are animals that eat consumers and fill the plant-eating niche. E.g.. Cows,
Carnivores: are animals that eat other consumers and fill the meat-eating niche. E.g..
Wolves, coyotes, sharks
Predators: kill and eat other animals ( cougar, etc)
Prey: get killed and eaten by predators (mouse, feeder guppies)
Omnivores: Eat both producers and consumers (e.g. Raccoon, Skunk, and humans)
Food Chain is a model that shows how energy is stored in food passes from organism to
organism. (See figure 1.30 in text)
Food Webs are even more complex than food chains, they show all of the relationships
between predator and prey in an ecosystem (they are a combination of several food
Food Chains and Webs show how food energy moves throughout the system but not how
many organisms it involves. To solve this, scientists invented the pyramid of numbers,
which states how many organisms are involved at each level.
Biomass: the total mass of all the organisms in an ecosystem

Clean-Up Squads
Scavengers: are organisms that feed on dead or decaying plant and animal matter.
Decomposers: don’t actually eat dead material, instead they grow on or in dead material,
absorbing some nutrients into their own cells.
Topic 5 – Cycles in the Environment

Evaporation: is the process in which a liquid changes into water vapour. Liquid water
evaporates to form invisible water vapour.
Transpiration: is the process in which water that is taken in through a plants roots
evaporates from the plant’s leaves, stem, and flowers.
Condensation: is the process in which water vapour changes into a liquid.
Precipitation: is the process in which liquid water forms from condensation occurring
inside clouds and then falls as rain, sleet, snow, and hail.
Ground Water: is water in the soil. Plant roots can grow down to reach ground water.
People can reach ground water by digging wells.
Run-off: is water that runs off the ground into lakes, rivers, or streams.
Pollution: occurs when a substance is added to the environment at such a fast rate that it
cannot be broken down, stored, or recycled in the air, land, or water in a non-damaging
Acid rain: occurs when pollutants containing sulfur and nitrogen are found in high levels
in the air.
The Movement of pollution:
*Chemicals like DDT and PCB (polychlorinated biphenyl) take a very long time to
breakdown in the environment, this causes a great deal of damage plants and animals.
Bioaccumulation: When pollutants move from level to level in the food chain. (see figure

Topic 6 – Succession and Change in Ecosystem
Succession: the gradual process by which some species replace others in a ecosystem.
Primary Succession: is the gradual growth of organisms in an area that was bare, such as
rock. E.g.. Lichens produce acids that breakdown the rocks, then ferns and mosses begin
to grow.
Secondary Succession: The gradual growth of organisms in an area that previously had a
number of organisms. E.g.. A burnt forest area is an example of secondary succession.
Biological Control: controlling pests using their natural enemies.
Problems with Introduced Species
When exotic species (occur naturally in a different part of the world) are introduced to an
environment where they have no natural enemies they can often survive and reproduce
better than the native species and therefore take over. E.g.. Zebra mussel
Extinction: when a species no longer exists anywhere in the world.

Topic 7 – Environmental Monitoring
Ecosystem Monitoring: is a way to check the condition of an ecosystem by comparing the
results of investigations done at different times
Four Main Ways
-Physical Monitoring: uses satellites to track changes in landscape over time
-Environmental Monitoring: tracks changes in climate, temperature, and weather patterns.
-Chemical Monitoring: assesses air, soil and water quality
-Biological Monitoring: tracks changes in organisms and populations of organisms over
Indicator Species: a species that is sensitive to environmental change and is the first to be
affected; they help to monitor the overall health of our environment.
Baseline Data: a starting point of data that allows scientist to go back and see if changes
have occurred.
Permanent Plots: study areas that scientists always return to.
A report that outlines how an activity will affect the environment is called an
Environmental Impact assessment.

Unit 2 Plants for Food and Fibre – Study Guide
Topic 1 – People and Plants
Plants are used by humans for food and fibre
Fibre: is the tissue of plants from the stem, leaves, seeds, and roots

Plants have numerous uses, some examples include
- using carbon dioxide and giving off oxygen
- the base of most food webs
- shelter
- cleaning and filtering water
- prevention of soil erosion
Plants for food
75% of the world’s food supply is based on seven crops
- Wheat                - rice          -maize (corn)          - potatoes
-Barley         -cassava       -sorghum
Plants and final products
Cocoa tree – chocolate
Canola – vegetable oil
Seaweed – ice-cream, yogurt
Sugar beets – sugar
Plants for Fibre
Cotton – used for clothing, plastics, and papers
Hemp – the oldest cultivated plant in the world, the first bible was printed on hemp.
Early sails and ropes were made of hemp.
Advantages of Hemp
- Can be harvested in one year
- hemp paper can be recycled 7 times longer than wood paper
- not eaten by most insect pests
Flax – 2-3 times as strong as cotton
Used in varnishes and some types of linoleum
Plants for Medicine
More than 7000 medicines today are made from plants
White willow bark – aspirin – pain relief
Opium poppies – morphine – strong pain killer
Cinchona trees – quinine – used to prevent malaria

Plants for transportation and Construction
Rubber Trees – brought about tires, which has enabled cars, planes and spacecraft
Wood is used in construction around the world
Plants are also used for fuel – ethanol-blended gasoline, coal for furnaces and electricity.

Topic 2 – Structure and Adaptations
Plant roots – often the plant is the tip of the iceberg
Roots perform several important functions
- they absorb water and minerals
- they support and anchor the plant
- they store food for the plant
Taproot: main root, which can reach deep into the ground with numerous small roots,
coming out of it.
Root hairs: increase the surface area in which the plant can absorb water and nutrients.
Fibrous Roots: shallow system of similar sized roots that quickly soak up moisture.
Carrots, beets, turnips, radishes and parsnips are all edible roots
Diffusion and Osmosis
Two key functions that allow roots to absorb water and dissolved substances
Diffusion: a tendency of particles to move from an area of high concentration to an area
of low concentration. E.g.: air particles of perfume spread throughout the room.
Differentially Permeable Membrane: allows some materials to pass through, yet keep
other materials out. E.g. Marbles and sand in a mesh bag.
Osmosis: a type of diffusion in which water moves form a high concentration to a low

Functions of the Stem
- transport water and nutrients between the leaves and the roots
- provide support for the plant
- food storage

Leaves – the energy producers of the plants
Leaves contain chlorophyll the pigment that makes them green.
Photosynthesis takes place in the leaves.

CO2 + H2O + Sunlight + nutrients ----- sugar + O2

Gases like carbon dioxide and oxygen enter and leave the plant through little openings in
the leaves called stomata. Guard cells around the stoma (singular of stomata) regulate
how much comes and goes.

Respiration: process by which plants release CO2 and take in O2, this takes place at night
and is slower than photosynthesis (good thing)
Transpiration: the loss of water from a plant through evaporation, acts as a pump using
osmosis to move water up the stem of the plant.

Topic 3 – Plant reproduction and Breeding

Selective Breeding: people choose specific plants with specific characteristics and
encourage these plants to reproduce.

Canola- made by using selective breeding of rapeseed.
Genes: the part of the cell that controls plants characteristics.
Types of Reproduction
Sexual: involves the specialized seeds and fruits of two plants
Asexual/vegetative reproduction: occurs when a parent plant grows plants from its roots,
stems, or leaves.
         E.g. Grafting, taking the branch of one tree and attaching it to another.
Seed Plant Reproduction
Cones: the part of the tree that has a series of woody scales.
Female cones contain ovules (eggs); Pollen grains containing sperm develop on the
smaller male cone. When these two meet the sperm swims down the pollen tube and
fertilizes the egg
Pollination: The process of pollen travelling to the female cone.

A flowers main job is to attract insects that will spread the plant pollen to other plants.
Parts of a Flower
Stamen: male part of the flower
Pistil: female part of the flower
Petals: usually brightly coloured
Sepals: green parts found underneath the flower
The pistil has three main parts:
Stigma: sticky tip of the pistil that catches pollen
Style: the tube connecting the stigma and the ovary
Ovary: a tiny chamber that holds the ovule (eggs).
Each Stamen has two parts:
Filament: the stalk
Anther: tip, produces pollen

Pollination 3 steps
1) Pollen grain lands on the stigma
2) A pollen tube grows down the style into the ovary and enters an ovule
3) A sperms travels down the tube to fertilize the egg.

Seed to Fruit
Once a plant is pollinated a seed is formed, inside the seed is a tiny living plant called an
embryo which is surrounded by food to keep it alive.
Fruit: a growing ovary of a plant, which swells and protects the seeds until they are ripe.

How seeds are dispersed:
- carried by animals and insects
- carried by winds or water
- Humans use machines to efficiently plant crops
This can take place in many creative ways *see page 127 for more
Germination: is the development of a seed into a new plant.

Topic 4 – Meeting the Need for Food and Fibre

Canada is one of the leading exporters Food and Fibre in the World.
Sustainability: being able to grow food and fibre while keeping our natural systems
healthy for long term.
Crops in Alberta
Wheat: ground up for flour
Barley: Fed to livestock, Used for making Malt.
Oats: mostly fed to livestock some for breakfast cereals
Legumes: Such as Peas, Faba Beans and Lentils, all high in protein
Canola: used to make margarine, salad dressing etc.
Potatoes: french fries, potato chips
Alfalfa: feeds livestock, strong root system
Specialty Crops: ginseng, beans, safflower, and spices

Farming Practices
Irrigation: watering crops using a system of large pipes and sprinklers
Monoculture: growing only one type of plant in the field for greater efficiency
*Copy Chart pg. 141

Forestry is a major industry in Canada
Diversity: variety of plants and animals in an ecosystem
Common Alberta Trees
Lodgepole Pine: largely used in construction
White Spruce: used in plywood, pulp and paper
Black Spruce: lumber and strong paper
Aspen: good for furniture, pulp and paper
White Birch: Furniture and Firewood
Tamarack (Larch): has a fungus that resist decay, so it is used on fence posts and railway
*Check out pie charts and tree pictures on Pg. 145

Steps in Harvesting Trees
-Planning the cut (based on careful review of the site)
-Building a road into the area
-Felling and delimbing trees
-Dragging the logs to a central loading point
-Hauling the logs to sawmill
-Preparing the site for reforestation

Global Problems
Erosion: Soil that is blown away by wind and water
Desertification: as a result of drought desert takes over agricultural land

Topic 5 - Sustaining the Soil
Developing Soils – five main factors affect how soil develops:
1) parent material
2) vegetation
3) landscape
4) climate
5) time

Humus: a dark soil rich in nutrients holds water well
Healthy soil needs decomposers to break down dead organisms so plants can use the
nutrients. There are four key types, which work differently:
1) Bacteria – actively break down dead material
2) Fungi – make nutrients available to plants
3) Microscopic actinomycetes – special kind of bacteria that help to create humus
4) Earthworms –grind, digest and mix soil.

Healthy Plants require six nutrients
-Nitrogen      phosphorous           potassium
 Sulfur        calcium               magnesium

Challenges and Solutions
Salty Soil – caused by too little vegetation and two much water
Solution: replant areas so the water can’t dissolve the salt and leave it behind

Soil Erosion – caused by too much cultivating mixed with water and wind
Solution – leaving a root system in place to hold the dirt, zero tillage, shelter belts, crop

Hydroponic Technology
- Growing plants without dirt, high energy cost
Topic 6 – Pests and Pest Control
Pest: any organism that humans find annoying or harmful
Dandelions – the most successful plant pest, here’s why
1) Powerful roots
2) Broad leaves
3) Super seeds
4) Adaptable
5) Chemical weapons

Check Wanted Poster on Pg. 166
Introduced Species: species not common to an area (often with no natural enemies)
Pests were controlled by herbicides, insecticides, fungicides, and a bunch of other
“cides”. Problems are associated with all of these chemicals
E.g. bioaccumulation, and poisoning “innocent” species
On top of this, Some pests are becoming resistant to chemicals

Organic Food: food grown without the use of pesticides or chemical fertilizers.
The need for chemicals is reduced by:
-Sowing good quality seeds
-Removing weeds early
-Cutting weeds along property edges
-Cleaning equipment so that it doesn’t transfer weeds.
-Using biological controls

Unit 3 – Heat and Temperature
Topic 1 – Using Energy for Heat
Thermal energy: (heat) is the total energy of all of the particles in a material or object.
Throughout the ages people have invented a variety of devices to help create and capture
heat for use.
Topic 2 – Measuring Temperature
Thermometer: Mechanical or electrical devices for measuring temperature.
Early Thermometers were invented by Galileo.
Scale: A series of equally measured sections that are marked and numbered for use in
Celcius Scale: temperature system most commonly used in Canada and many other parts
of the world. Unit of temperature is called a degree.
Freezing Point: 0 degrees at sea level on the Celcius scale, the temperature at which water
Boiling Point: 100 degrees at sea level on the celcius scale, the temperature at which
water boils.
Kelvin Scale: a scale used for measuring temperatures in scientific experiments. On the
Kelvin scale, water freezes at 273 K and boils at 373K, the coldest possible temperature
(also known as absolute zero) is 0 K.

Most thermometers contain these components;
Sensor: a material which is affected by changes in some features of the environment,
such as temperature.
Signal: information about temperature, such as an electrical current
Responder: a pointer, light, or other mechanism that uses the signal in some way.

Thermocouple: wires made of two different metals are twisted together so that a small
electrical current is generated, the strength of the current depends on temperature. Used
to measure high temperatures.
Bimetallic Strip: two different metals joined together firmly. When heated, one metal
expands more than another does and the strip curls up. (commonly used in thermostats in
Recording Thermometer: bimetallic strip connected to a writing device and paper which
records temperature fluctuations over time.
Infrared Thermogram: records infrared radiation, (heat sensor) as different colors
according to their temperature.

Topic 3 – The Particle Model, Temperature, and Thermal Energy

The Particle Model:
- All substances are made of tiny particles too small to be seen
- Particles are always in motion
- Particles have spaces between them

The motion of particles increases as temperature increases and decreases as temperature
*Temperature indicates the average speed of particle motion in a substance.

Energy: is a measure of something’s ability to do work.
Two Principals apply whenever change occurs:
- changes happen when there is a difference in energy
-   Energy is always transferred from a high-energy source to something with a low
    energy source.

Law of Conservation of Energy (important)
Energy cannot be created or destroyed, only transformed from one type to another or
passed form one object to another.

Topic 4 – Expansion and Contraction
Contract: decrease in volume
Expand: Increase in volume
Temperature changes cause things to expand and contract
Heated – usually causes expansion
Cooled – usually causes contraction

Usually more drastic changes in gases, then liquids, then solids.
Topic 5 – The Particle Model and Changes of State
Heat Capacity: amount of thermal energy that warms or cools the object by one degree
Specific Heat Capacity: amount of thermal energy that warms or cools one gram of a
material by one degree Celcius.
*See Table 2 pg. 218

Changes of State


Sublimation                                           condensation

                       Melting (also called fusion)
       Solid                                                         Liquid
                       Freezing (also called solidification)

Melt: turn from a solid to a liquid
Freeze: turn from a liquid to a solid
Evaporate: turn from a liquid to a gas
Condense: Turn from a gas to a liquid
Sublimation: turn from a solid to a gas or a gas to a solid.

Evaporative cooling: a process in which the faster-moving particles on the surface of a
liquid evaporate and escape into the air, the slower ones are left behind creating a lower
average kinetic energy (cooling it).

Particles are less organized as the energy increases. This means the warmer the
substance, the more disorganized the particles.
Phase Changing
During a change from solid to liquid or liquid to gas the average temperature does not
change even though heat is being added, the name for the heat that is added is Latent heat

Topic 6 – Transferring Energy

There are three Main ways to transfer energy

Energy Source: an object or material that can transfer its energy to other objects.
Radiation: the transfer of energy without any movement of matter.
Radiant energy: (also known as electromagnetic radiation or EMR for short) Energy that
is transferred by radiation.

All of the forms of Radiant energy share several characteristics:
- They behave like waves
- They can be absorbed and reflected by objects
- They travel across empty space at the same very high speed 300000 km/s
Conducting Energy Through Solids
Thermal Conduction: the process of transferring thermal energy through direct collisions
between particles.
Heat Insulators: are very poor conductors
Fluid: Materials that can be poured or that flow from place to place.
Convection: A warm fluid, moves from place to place, carrying thermal energy with it.
Convection Current: a moving fluid.

* Know Energy Transfer Diagram (Figure 3.26 on pg. 232)

Topic 7 – Sources of Thermal Energy

Energy appears in many forms.
Potential energy: Stored energy
Two examples of this type are:- gravity (a rock sitting on a counter)
                                - elastic (pulled back and ready to be shot).
Kinetic energy: Energy of motion. (the energy present in a moving object)
Chemical energy: is the kind used by our body (complex sugars are broken down to
provide your muscles with energy). It can also be found in batteries (which also have
potential energy).

Different forms of energy can be converted into another form.
       e.g. a candle can convert chemical energy into heat and light (candles are energy
Energy Converters: Devices that convert or change energy from one form to another.
Mechanical Forces- is a source of thermal energy caused by friction (car engine)
Geothermal Energy: energy that can we harness from the Earth’s interior.
Electrical Converters- Generate electrical Energy
Dams: Gravitational potential energy of water held in reservoirs converted into electrical
Coal: Chemical energy is turned into thermal, which converts into electrical

Solar Energy – 2 types:
Passive Solar: using materials and in the structure to absorb, store and release solar
Active Solar: Convert light energy absorbed by solar collectors into electrical (much like
plants do)
Wind Energy: the energy of moving air which can be harnessed through the use of
Fossil Fuels: chemicals made from plants and animals that died and decomposed millions
of years ago and have preserved deep underground.

Problems with Fossil Fuels

Global Warming: when fossil fuels are burned and released into the air, the CO2
concentrations increase, which trap heat.
Thermal Pollution: accidentally warming up the environment.
Cogeneration: using waste heat to heat needed areas, generate electricity and do other
useful tasks.

Topic 8 – Conserving Our Fossil Fuel Resources

There are many things that we can do to conserve energy
-Insulate homes and water lines
-Reduce the amount of energy we use (take shorter showers etc.)
-Install a programmable thermostat
-Many other things

*See Figure 3.43 on page 252 to learn how a refrigerator works.

Unit 4 – Structures and Forces

Topic #1 – Types of Structures

Structures – things with a definite size and shape, which serve a definite function.
Natural Structures – are not made by people - e.g. feathers, sand dunes.
Manufactured Structures – things that are built by people – e.g. Calgary Tower, spoon.

Structures can be classified according to how they are built. Three kinds of designs for
structures exist. These are:
1. Mass Structures – are made by piling up or forming similar materials into a particular
shape – e.g. dams, brick walls, cakes, breads.
2. Frame Structures – the body of most buildings have a skeleton of very strong
materials, which support the weight of the roof and covering materials – e.g. house frame.
3. Shell Structures – these objects are strong and hollow. They keep their shape and
support loads without a frame or a solid mass inside – e.g. eggs, igloos, bottle, pipe.
(These objects have a thin outer layer that is carefully shaped to provide strength.)

Some manufactured structures are combinations of Frame and Shell structures – e.g.
football helmets, airplanes, the Calgary Golf Dome.

Topic 2 – Describing Structures

When designers or engineers plan new projects they must consider the structures:

1) Function – this is the job that the structure is designed to do e.g. a train bridge is
   designed to support the weight of the train.
2) Aesthetics – making a structure look good. The best designs not only serve their
   purpose but they are also “aesthetically pleasing” meaning they look good.
   (Aesthetics – the study of beauty in art and nature)
3) Safety – almost all structures are built with a large “margin of safety”. This means
   that structures are designed to withstand much more pressure than they would
   normally need to deal with e.g. a bridge can hold much more weight than it ever
   would have to.
4) Balancing Cost with Safety – it is difficult to design safe, well built projects that are
   not too expensive.
5) Materials – the properties of the material must match the purpose of the structure e.g.
   you would not build a bridge for cars out of rubber.

Composite materials – are made from more than one material e.g. concrete can be
reinforced using steel rods.
Layered materials – layers of different materials pressed or glued together often produce
useful products. These layers are called “laminations” e.g. layers of a juice box
container involve paper, plastic and aluminum foil, making it lightweight, waterproof,
and airtight.
Woven and Knit materials – weaving and knitting are effective ways to make flexible
materials. E.g. yarn in dishcloths is woven together to be flexible & strong

  When engineers choose what materials to use when building structures they must
1) Cost of the material          3) Environmental Impact
2) Appearance                    4) Energy Efficiency

Joints – this is where a structures parts are joined together.
Mobile Joints – joints that allow movement. These hold parts together while still
allowing movement e.g. elbows, door hinges
Rigid Joints – attach parts of a structure without allowing movement. These types of
joints fall into 5 categories:
- Fasteners – nails, bolts, screws
- Interlocking Shapes – Lego bricks, some pavement stones
- Ties – thread, string, rope
- Adhesives – glues (thermosetting – harden when cooled, solvent based – harden when
- Melting – welding or soldering materials together

Topic 3 – Mass and Forces

      The mass of an object is the measure of the amount in it.
      A balance is the most common type of measuring instrument for mass.
      Forces are stresses such as pushes or pulls.
      Standard unit of force is called Newton (N). Eg: 1N is a small force. Just enough
       to stretch a thin rubber band.
      Force Meter (spring scale) – a common laboratory instrument for measuring
       forces. However, this scale is not very accurate.
      To describe force, you need to determine both its direction and its size.
      Gravitational Force – the force exerted by gravity on an object; measured in
       Newtons (N). This is the scientific term for the everyday term “weight”.
      Force Diagram – a simple picture that uses arrow to show the strength and
       direction of one or more forces.

Topic 4 – Forces, Loads and Stresses

External Forces – are stresses that act on a structure from outside it Eg. Your kick when
striking a soccer ball. These forces produce:
 Internal forces - which are stresses, put on the materials that make up a structure.
Internal forces are the result of external forces.
Internal stresses can change the shape of a structure. This change of shape to a structure
is called Deformation.

External Forces
Dead load – a permanent force acting on a structure. Over time can cause the structure to
sag, tilt or pull apart.
Live load – a changing or non-permanent force acting on a structure Eg. snow, weight of
vehicles or people (Impact forces are a type of live load).

Internal Forces
Tension forces – stretch the material by pulling its ends apart.
    - Tensile strength – measures the largest tension force the material can stand before
Shear forces – bend or tear the material by pressing different parts in opposite directions
at the same time
     - Shear strength – measures the largest shear force the material can stand before
Compression forces – crush the material by squeezing it together.
     - Compressive strength - measures the largest compression forces the material can
        stand before losing its shape or breaking.
Torsion forces – twist the material by turning the ends in opposite directions
     - Torsion strength – measures the largest torsion force the material can stand and
        still regain its original shape.
Bending forces – are a combination of tension and compression forces.

The strength of a material is dependent on the forces between its particles.
Eg. Steel has high tensile strength while rubber has high torsion strength.

Topic 5 – How Structures Fail

   If a great enough force is applied to a structure, it will begin to fail.

Levers create large forces – a lever is a device that can change the amount of force
needed to move an object (e.g. with a crowbar, you can lift very heavy objects. Some
levers consist of a long arm that rests on a pivot or fulcrum)

Materials Fail: external forces can cause internal forces in the structure. These internal
forces can cause the following types of damage:

- Shear ( wieght of building causes soil to shear and the building to collapse)
    - Bend or Buckle ( a tin can will bend or fold up when it is compressed)
    - Torsion (twisting can lead structures to break apart or become tangled)

Materials that snap, break, bend, and shear can be put to good use in the following ways:
Buckle – car bumpers and sheet metal used in cars are designed to buckle in a collision.
Therefore the car becomes badly damaged but the people in the car may not be badly
injured because the metal crumpled and absorbed the energy of the collision.
Shear- in a boats outboard motor, the propeller is held to the engine with a shear pin.
This pin breaks if the propeller gets tangled in weeds. This is done to save the engine.
Twist – spinning cotton or wool fibres very tightly together can make very strong fabric.
Controlled twisting can turn string into ropes

Metal Fatigue – this is when metal weakens due stress. Is process often results in the
metal cracking and breaking.
Topic 6 – Designing with Forces

 Designers often rely on one of three key methods to help structures withstand forces:
1) Distribute the load throughout the structure so that no single part is carrying most of
    the load.
2) Direct the forces along angled components so that the forces hold pieces together
    instead of pulling them apart.
3) Shape the parts to withstand the specific type of force they are likely to experience.
(Examine 3 structural problems and their solutions on pgs. 321/322)
 Structures can be strengthened by using materials that are appropriate for their
    function ex. in a swing set – use a rope or chain that has high tensile strength to attach
    the seat to the frame.
Friction – a force that resists, or works against the movement of two surfaces rubbing
together ex. brick wall – each layer of bricks rests on the layer below. This “friction”
holds the bricks in place.
- frictional forces are greater between rough surfaces.
Topic 7 – Stable Structures
     A stable structure is one that is not likely to tip or fall over.
    Center of Gravity – the point at which all of the gravitational force of an object may
    be considered to act.

      It is important that home builders understand the properties of the ground they are
       building on. If they do not, then the houses that they are building can be damaged
       by the shifting soil.

Constructing stable structures on shifty ground

   1. Find something solid – below the soil lies solid bedrock. Builders can build
      solid foundations on the bedrock, or they can sink large metal, concrete or wood
      cylinders into the soil to rest directly on the bedrock.
   2. Make a solid layer – Road builders always pack loose surface soil before paving
      to create a solid base for the asphalt or concrete (packed gravel foundations are
      also useful for road construction).
   3. Spread the load – If the weight of the structure is spread over a large area, any
      particular part of the ground supports only a small part of the weight ex. This is
      why footings (concrete foundations beneath houses) are wider than the walls

   Spin Stabilization – the tendency of an object that is spinning on its axis to move in
   a predictable manner ex. the faster a bicycle wheel spins the more stable it is.
   (pg. 340)
Unit 5 – Planet Earth

Topic #1 – Minerals
Rock – is made up of one or more pure, naturally occurring, non-living, crystal like
materials called minerals.
Earths Crust – the thin outermost layer of the earth
- A mineral can be called an element (a pure substance) or a compound (two or more
elements combined)
The Mohs Hardness Scale – a scale developed to identify minerals according to how hard
they are. A mineral that is rated as a 1 is very soft and a mineral that is rated a 10 is very
hard (Gold is a 10 – the hardest mineral).
Crystals – are the building blocks of minerals. A mineral’s crystals are used to help
people identify it (Figure 5.2 on pg. 355 illustrates the six major crystal systems).

Other clues to mineral identification

   -   Lustre – the “shininess” of the mineral
   -   Color – the color of the mineral can be used to identify it. However, a mineral
       will be a different color if it is pure versus if it is not.
   -   Streak – is the color of the powdered form of the mineral (this is a good way to
       identify fake gold)
   -   Cleavage and Fracture – the way a mineral breaks apart can be a clue to its
       identity. If it breaks along smooth, flat surfaces, it is said to have cleavage. If it
       breaks with rough or jagged edges it is said to fracture.

Unit #2 – Rocks and the Rock Cycle

Igneous Rock - forms when hot magma or lava cools and solidifies. Magma is melted
rock found below the earth’s crust where temperatures are high. When magma cools and
hardens below the earths surface it is called intrusive rock (ex. Granite). When magma
breaks through the earth’s surface in a volcanic eruption, it is called lava. Rock that
forms when lava cools is called extrusive rock.

Sedimentary Rock – makes up about 75% of all rocks that we can see on earth. This
kind of rock is made from sediments, which are loose materials, such as bits of rock,
minerals, and plant and animal remains that get packed in layers and cemented together.
The arrangement of these layers is called stratification. The process of squeezing these
layers together is called compaction. In some rocks, minerals dissolve as water soaks
into the rock, forming a natural cement that sticks pieces of sediment together (this is
called cementation).

Metamorphic Rock – meaning “changed form”. This type rock may be formed below
the earths surface when extremely high pressures and heat cause the original rock or
parent rock to change form.
The Rock Cycle – rocks continue to change in an ongoing process (see figure 5.19, pg.
368). Rocks change as a result of the rock cycle. In order to identify rocks after they
have been weathered, you need to identify the minerals found within the rock.

- Soil is formed from the combination of compost (which is decaying plant matter), rock,
sediments, living material like twigs and leaves and dead worms or insects. The dark-
colored portion of soil is called humus and is very fertile.

- Layers of soil make up a soil profile. The top layer is called topsoil (it consists of
humus and small grains of rock). The second layer is lighter in color, and contains less
humus and larger rock chunks. The third layer contains even larger rocks that are only
beginning the process of being broken down into soil.

Topic #3 – Erosion

Erosion – is the movement of rock and mineral grains from one place to another.
Sediment – comes from larger rocks that have been broken down or worn away through
Sedimentation – the process were eroded material is deposited and built up.
Mechanical Weathering – is the physical break-up of rocks (Ex. Gravity causes rocks to
fall down a cliff and break apart. These rocks rub against each other and become
smoother and rounder). Frost wedging – during the daytime in the spring water runs into
cracks in rocks. Then at night the water freezes in the cracks and pushes the rocks apart.
Each day more water runs into these cracks until eventually the rock breaks apart.
Chemical Weathering – breaks down minerals through chemical reactions (Ex. Acidic
rain works to break down some rocks like limestone & dolomite).
Biological Weathering – is the physical or chemical breakdown of rock caused by living
organisms, such as plants, animals, bacteria and fungi (Ex. Plant roots wedge into rocks
by forcing themselves into cracks. As the root expands the rock is pushed apart).

       Mechanical, Chemical and Biological weathering work together constantly to
        change our landscape.

       Glaciers, gravity, wind and water all cause erosion. Changes in our earth’s
        surface that happen slowly (those caused by glaciers) are called “gradual
        changes”. Those that happen quickly like floods, landslides and rockslides are
        called “sudden changes”.

       Water in motion is a very powerful cause of erosion (Ex. Rivers erode their banks
        and carry with them large amounts of soil).

Topic #4 - The Moving Crust

   The earth’s crust is the layer of the earth that we walk on and build our homes on. It
    also includes deeper areas where minerals and oil and gas are mined.
   The mantle is found under the crust. It is made of rock material. The upper mantle is
    solid and the lower mantle has the consistency of taffy. The earth’s crust and the
    upper mantle form the lithosphere.
   The outer core is under the mantle and consists of iron and nickel. The temperature
    here is 5500 degrees Celsius and is so hot that iron and nickel are in a liquid state.
   The intense pressure of all the layers forces the inner core to have a temperature of
    over 6000 degrees Celsius.

Continental drift – the belief that the continents at one time where completely joined
together and over the years have drifted apart.

-   A German scientist named Alfred Wegener found evidence that supported his theory.
    This evidence came in the form of rock similarities, fossil similarities, and climatic
    similarities between continents. Wegener believed that all of the earth’s continents
    had been joined together in a giant supercontinent called “Pangea". He had difficulty
    proving this theory and died in 1930 still trying to prove it.

Sonar (sound wave technology) – revealed to scientists that the ocean’s floor is not flat. It
revealed that mountain ranges exist on the ocean floor.

Sea floor spreading – the process in which an ocean floor slowly increases in size over
time because of the formation of new igneous rock along a fault (pg. 388). The ocean
floor is spreading and getting wider by about 2cm per year (about the same speed at
which your fingernails grow).

Theory of plate tectonics – states that the earth’s crust is broken up into pieces called
plates. These plates are always moving on the earth’s mantle. Plates that are moving
together are called converging plates and plates that are pulling apart are called diverging

- One explanation for why plates move is based on the theory that a convection current is
causing the earth’s plates to move. (see diagram on pg. 392/393)

Topic #5 - Earthquakes

       Scientists use a machine called a seismograph to measure earthquakes. This
        machine is attached to bedrock in order to feel vibrations that result from an
        earthquake (see diagram of seismograph on page 397).

       Seismologists (scientists who study earthquakes) use a method of measurement
        called the Richter Scale to describe the strength of the earthquake. The smaller
        the number the less devastating the quake. Most earthquakes that cause damage
        and loss of life register between 6 and 8 on the Richter Scale.

       The energy waves that travel outward from the source of the earthquake are called
        seismic waves. Aftershocks are smaller quakes that happen after the initial quake.
Types of Earthquake Waves

Primary (P waves) – travel the fastest of all three types of waves and can pass through
solids, liquids and gases. These cause slight vibrations that rattle dishes and warn people
that an earthquake is taking place and that larger earth movement may be on it’s way.

Secondary (S waves) – travel more slowly than p waves and can only pass through

Surface waves – are the slowest of the three waves, but their rolling motion causes the
most damage. They break up roads and buildings, because they cause one part of a
structure to move up while the other part moves down. These waves travel outward like
the ripples in a pond when you throw a pebble.

Focus – is the place deep in the earth’s crust where the earthquake begins.
Epicentre - the place on the earth’s surface directly above the focus of the earthquake.

       Rock in the earth’s surface is under intense pressure. When bedrock breaks
    suddenly a fault is created. Faults occur where tectonic plates meet. Three kinds of
    faults can occur:

- Normal fault – occurs because of tension forces (rock being pulled apart). In this type
of fault, rock generally moves down.
- Reverse fault – occurs because of compression forces (rock being pushed together). In
this fault, rock generally is forced upward.
- Strike-slip or Transform fault – occurs because of shear forces. Rock along the edges of
these faults generally have many bumps and bulges.

       People who live in earthquake zones have to prepare for quakes by doing things
    like bolting pictures to walls and by using steel and wood in the construction of their
    homes (wood and steel can bend slightly without breaking where as concrete can not).

Tsunamis – huge title waves that are caused by earthquakes that take place under the

Topic 6 – Volcanoes

   A volcano is an opening in the Earth’s crust that releases lava, steam, and ash when it
    erupts (becomes active).
   The openings in the earth’s crust when a volcano erupts are called vents. When
    volcanoes are not active, they are described as dormant.
   Volcanoes are formed when rock surfaces beneath the earth’s surface push against
    each other. The rock pushing downwards begins to melt and turn into magma.
    Eventually there is so much magma that it is forced up through cracks in the earth’s
    crust and an eruption occurs.
   Volcanoes erupt in stages over a period of weeks, months, or even years.

Famous Volcanoes

-   Mount St. Helens (U.S.A.) erupted in 1980.
-   Mount Vesuvius in Italy has been dormant since 1944 and scientists believe that it is
    set to erupt any time.

Topic #7 – Mountains

   Sedimentary rocks that are places under slow, gradual pressure can either fold or
    break. Rock that has been heated and is soft begins to fold. The top part of this
    folded rock is called the anticline, and the bottom of the fold is called the syncline
    (see figure 5.67, pg.413)
   If the rock is too brittle to fold, it can break, forming a fault. Faults can be the result
    of squeezing the earth’s crust or of stretching the earth’s crust.
   When the earth’s crust is squeezed together, sedimentary rock forms into slabs that
    move up over each other like shingles on a roof. This process is called thrust faulting.
   When the earth’s crust is stretched blocks of rock can tilt and slide down. Here, older
    rocks may end up on top of younger rock, and these huge amounts of rocks can form
    mountains called fault block mountains.
   The Canadian Rockies have been formed by sedimentary rock sliding on the
    basement rock and pushing the crust upwards (Sedimentary rock is seen at the
   The American Rockies have been formed by igneous and metamorphic (basement
    rock) rock being shoved on top of each other and pushed upwards (Basement rock is
    seen at the surface).

Ages of Mountains

-   Young mountains are jagged at the top.
-   Older mountains are more rounded because their surfaces have been eroded and
    weathered due to mechanical, biological and chemical weathering (The Canadian
    Rockies are fairly young, the Laurentian Mountains in Quebec are older and are in the
    process of being worn down).

Topic #8 – Fossils

   Fossils provide clues about when life began, and when plants and animals first lived
    on the land.
   A fossil is formed when soft parts of a dead animal (skin, muscles and organs) decay
    quickly, but the hard parts of the animal (teeth, bones and shells) are altered and then
   Bones of the animal become petrified or turned into a rock like substance. This
    happens when water penetrates the bones of the dead animal and dissolves the
    calcium carbonate in the bone. Then a very hard mineral (silica) is deposited and left
    behind. This mineral turns the bones into a rock like substance.
   Sometimes the actual organism or parts of it may be preserved as a fossil. These are
    called original remains (ex. fly’s preserved in resin, dinosaurs preserved in tar pits
    and woolly mammoths preserved in ice.)
   Trace fossils are evidence of animal activity (ex. Footprints, or worm holes that have
    become fossilized).
   A mould is a type of fossil, in which the hard parts of the organism have dissolved,
    leaving a cavity in the rock.
   A cast is a type of fossil in which sediments or minerals have filled a mould and
    hardened into rock.

Topic #9 – Geological Time

   Principle of superposition states that in undisturbed layers of sedimentary rock, the
    oldest layers are always on the bottom and the youngest layers are always on the top.
   Strata is layers of sedimentary rock.
   Relative dating is a strategy that scientists use to figure out the age of the rocks
    according to their position in the strata.
   Index fossil – a type of fossil that can be used to determine the age of the material n
    which it is found.
   The half-life of a substance is the amount of time that a given amount of a radioactive
    substance takes to be reduced by one-half.
   Radiometric dating is the process of determining the age of a rock specimen by
    measuring the amounts of radioactive particles that are present in the rock and by
    knowing the half life of the parent rock.
   The geological time scale is a division of Earth’s history into smaller units based on
    the appearances of different life forms (Examine the illustrated geological time
    scale in figure 5.87 on page 426).

Divisions within the Geological Time scale

- Precambrian period – was the first 4 billion years that the earth existed until 590
million years ago (during this time the first super continent called Rodinia was formed)
- Paleozoic Era means ancient life (approximately from 590 million years ago to 248
million years ago)
- Mesozoic Era means middle life (approximately from 248 million years ago to 65
million years ago)
- Cenozoic Era means recent life (approximately from 65 million years ago to present

   It is believed that the second super continent Pangea first split into a northern portion
    called Laurasia and a southern portion called Gondwanaland.
Topic #10 – Fossil Fuels

   Petroleum is a type of oil found in rock formations in the Earth’s crust. It is refined
    into products such as gasoline or jet fuel (it is most often found in sedimentary rock).
   Fossil Fuels are fuels made of decomposed plants and other organisms that have been
    hardened and fossilized. Fossil fuels take millions of years to develop; examples of
    fossil fuels include oil, natural gas and coal.
   Bitumen is a heavy almost solid form of petroleum. Some bitumen deposits are
    found near the surface of the Earth and can be mined or heated and pumped to the
    surface (to be used as gasoline and or jet fuel).

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