AGF SciencePot

ROCkS & WEATHERING

2011-03-02T00:48:00.000-08:00

Prior Knowledge

You might see rocks in a cliff face or mountainside, but these are also rocks under the ground. Marble is one can you name two more?
Does water flow more quickly through sandy soil or clay soil?
Particles are arranged differently in solids and in liquids. Summarise these differences in a couple of sentences.
The pH scale describes how acidic or alkaline a solution is. Neutral solutions have pH 7. What is sort of pH does a weak acid have.
If you leave a bowl containing a solution of a salt in water, the water disappears, leaving the salt behind. Where has the water gone

Key Ideas

A rock is a mixture of minerals that occur naturally in the Earth's crust.
Rocks have different textures depending on how their mineral particles are arranged. Some rocks are porous - they have little spaces in their structure which can hold water.
Rocks can be worn away or weathered by conditions in the environment. Physical, chemical and biological processes wear away rocks. Changes in temperature can weather rocks physically. The acid in rain water can react with rocks and wear them away chemically.
Weathered fragments of rocks are transported away from where they fall. Sediments carried by water can be dropped or deposited many miles away.
Layers of sediments may be deposited on top of each other and become cemented together to form new sedimentary rock.

Earth

The earth has a central part called the CORE which is made of iron and a bit of nickle. The core is very hot.

Around the core is a hot semi-liquid rock layer called the MANTLE.
Covering the mantle is a cooler solid surface that we live on called the CRUST.

Minerals

Minerals are solid substances that make up the earth's crust.
Have a definite composition,a regular structure and more often a single colour.
Most minerals are compounds,a few are elements.

Rocks

A rock is a mixture of minerals.
The minerals are in grains
In some rocks the grains are large and you can see them.
If a rock has a mixture of grains it might look multi-coloured or speckled.
Other rocks are crystalline.They have smooth faces which reflect light and so appear shiny.the grains have formed crystals that fit together so you can,t see the individual grains.

Classifying rocks
Properties used to identify rocks

Colour
Hardness
texture
how they split up when hit(cleavage)
Chemical behaviour
The easiest way to classify rocks is by where they come from.
This splits rocks into 3 different types

Igneous Rocks
These are formed when the molten rock inside the Earth cools and solidifies.

PLANTS

2011-02-25T09:39:00.000-08:00

Plants are living organisms belonging to the kingdom Plantae.
They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae.
The scientific study of plants, known as botany

Green plants absorb light energy using chlorophyll in their leaves.
They use it to react carbon dioxide with water to make a sugar called glucose.
The glucose is used in respiration, or converted into starch and stored.
Oxygen is produced as a by-product.
This process is called photosynthesis.
Temperature, carbon dioxide concentration and light intensity are factors that can limit the rate of photosynthesis.
Plants also need mineral ions, including nitrate and magnesium, for healthy growth. They suffer from poor growth in conditions where mineral ions are deficient.

Photosynthesis

Photosynthesis is the chemical change which happens in the leaves of green plants.
It is the first step towards making food - not just for plants but ultimately every animal on the planet.
During this reaction, carbon dioxide and water are converted into glucose and oxygen.
The reaction requires light energy, which is absorbed by a green substance called chlorophyll.
Photosynthesis takes place in leaf cells. These contain chloroplasts, which are tiny objects containing chlorophyll.

Here is the equation for photosynthesis:

Plants absorb water through their roots, and carbon dioxide through their leaves. Some glucose is used for respiration, while some is converted into insoluble starch for storage. The stored starch can later be turned back into glucose and used in respiration. Oxygen is released as a by-product of photosynthesis.

Factors limiting photosynthesis

Light intensity
Carbon dioxide concentration and
Temperature.

Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of water and carbon dioxide. Increasing the light intensity will boost the speed of photosynthesis.
Photosynthesis is limited by the concentration of carbon dioxide in the air. Even if there is plenty of light, a plant cannot photosynthesise if there is insufficient carbon dioxide.
If it gets too cold, the rate of photosynthesis will decrease. Plants cannot photosynthesise if it gets too hot.

Maximising growth
Farmers can use their knowledge of these limiting factors to increase crop growth in greenhouses. They may use artificial light so that photosynthesis can continue beyond daylight hours, or in a higher-than-normal light intensity. The use of paraffin lamps inside a greenhouse increases the rate of photosynthesis because the burning paraffin produces carbon dioxide, and heat too.

Plants and minerals
Plants need to take in a number of elements to stay alive. The most important are:
carbon
hydrogen
oxygen

Plants get hydrogen and oxygen from water in the soil, and carbon and oxygen from carbon dioxide and oxygen in the atmosphere. Water and carbon dioxide are used to synthesise food during photosynthesis. Oxygen is used to release energy from food during respiration.
In addition to these three elements, plants need a number of minerals for healthy growth. These are absorbed through the roots as mineral ions dissolved in the soil water. Two important mineral ions needed by plants are:

nitrate - for making amino acids, which are needed to make proteins
magnesium - for making chlorophyll

If a plant does not get enough minerals, its growth will be poor. It will suffer from deficiency symptoms:

deficient in nitrate - it will suffer from stunted growth
deficient in magnesium - it's leaves will turn yellow

The tomato plant on the left is healthy, the one on the right is growing in conditions where mineral ions are deficient

SOURCE

http://en.wikipedia.org/wiki/Plant
http://www.bbc.co.uk/schools/gcsebitesize/scien/add_aqa/plants/plants1.shtml

Mixtures & Compounds

2011-02-12T04:18:00.000-08:00

A mixture occurs when you combine matter in such a way where the components can be separated again.

A compound results from a chemical reaction between components, forming a new substance.

For example, you can combine iron filings with sulfur to make a mixture.

All it takes is a magnet to separate the iron from the sulfur.

On the other hand, if you heat the iron and sulfur you form iron sulfide which is a compound.

Here is How

First form a mixture - Stir some iron filings and sulfur to form a powder. You have just taken two elements and combined them to form a mixture. You can separate the components of the mixture by stirring the powder with a magnet - iron will stick to the magnet -

If you heat the mixture over a Bunsen burner, hot plate or stove, the mixture will start to glow. The elements will react chemically to form iron sulfide which is a compound. Careful! Unlike the mixture, the formation of a compounds cannot be undone so easily

What you Need

iron filings
sulfur powder
magnet
test tube or beaker
Bunsen burner or hot plate or stove

A compound is a material that is made up two or more elements chemically joined together.
For example , water is a compound made up of the elements hydrogen (H) and oxygen (O).

A compound such as water has particles called molecules.

Water

We can represent a water molecule by writing a chemical formula: H2O.

This tells us that a molecule of water contains two atoms of hydrogen joined to one atom of oxygen.
Water is made up of many identical water molecules.
Water is a liquid, so the molecules are close together.

Carbon dioxide

Chemical formula: CO2.
one carbon atom joined to two oxygen atoms make a molecule of carbon dioxide
Carbon dioxide is a gas, so the molecules are further apart than in water

Sodium chloride (common salt)

Formula - NaCl
There is one sodium particle for every chlorine particle
NaCl is a solid, the sodium and chlorine particles in it are close together with strong forces between them

The cards below show information about some materials. Some of them are elements and some are compounds.

Signs of a chemical reaction

ATOMS AND ELEMENTS

2011-02-04T04:44:00.000-08:00

Before starting this unit, you should already be familiar with these ideas from earlier work.

Matter is all the material in the Universe. Everything we know rocks, air,water, plants, animals andeven humans is made of matter. Matter can exst in three states as a solid, as a liquid and a gas.
If we cannot see and touch something in science, we can use a model to help show us how it works. What model have you used to represent circuits?

The particle model suggests that all matter is made up of particles. How are the particles arranged in a solids, liquids and gases?
Matter sometimes changes state from solid to liquid or liquid to gas and back again. Boiling is one change of state. List some others.
All matter is made up of tiny particles called atoms.
material that is made of only one type of atom is called an element.

Elements are found naturally on Earth and in space although some have been created in laboratories in recent times.
The elements were not all discovered at once, and some are very recent discoveries.

ATOMS

All matter is composed of atoms.

Atoms are the smallest pieces of a substance that can exist.

Atoms are very, very tiny. You cannot see atoms, not even with a microscope.

Scientist have done many experiments to find out about atoms.

They use the results of their experiments to develop theories or models to help us understand what atoms are like and how the behave.

At the centre of the atom there is a core called the nucleus .

The nucleus is made up of sub-atomic atoms (smaller than atoms) called protons and neutrons.

All around the core is an area of spinning electrons.

They remain in place because they are attracted to the opposite charge of the protons and the neutrons.

The protons have a positive charge and neutrons have no electric charge

Hydrogen atoms are the only atoms without neutrons

A normal atom has the same number of protons as electrons.

The atomic number of an atom tell you how many proton it has.

Atomic Number of Number of

Number = Protons = Electrons

Electrons are much smaller than protons, they weigh almost nothiing.

The atomic mass of an atom depends on the number of protons and neutrons in the nucleus

Carbon has an atomic mass of twelve.

The number of protons and neutrons is called the mass number of atoms.

Mass Number (A) = Atomic + Number of

Number(z) Neutrons

Ecological Relationships

2010-11-17T09:10:00.000-08:00

What Is Ecology?
Ecology is about the pattern of nature.
It is the study of the interactions among living organisms and their environment.

Every living thing depends on other things for survival.

What Is a Habitat?
A habitat is a place where an organism lives, and it provides the organism with the essentials of life so that it can carry out all the seven life processes.

A habitat provides animals with food, shelter and water
A habitat provides plants with light, water and a place to grow

Different habitats have different environmental condition such as temperature and amount of water.

the habitat of a plant or animal must provide all the things that it needs to live and reproduce.

Different plants and animals have different needs. For example a gerbil can survive on less water than a mouse. This is because it has the features that help it to survive. We say that it is adapted to its environment.

Classifying animals
When we put plants and animals into groups we say that we classify them.

Animals with backbones are called vertebrates
Animals without backbones are called invertebrates

Examples of Vertebrates

Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur

Reptiles are characterized by laying shelled eggs and having skin covered in scales. Reptiles are classically viewed as having a "cold-blooded" metabolism.

Birds are winged, warm-blooded, egg-laying, vertebrate animals.

Amphibians ( from Amphi- meaning "on both sides" and -bios meaning "life"), such as frogs, salamanders, and caecilians, are cold-blooded animals that develop from a juvenile water-breathing form, either to an adult air-breathing form, or retains some juvenile characteristics.

Fish is any aquatic vertebrate animal that is covered with scales, and equipped with two sets of paired fins and several unpaired fins. Most fish are "cold-blooded"

Examples of Invertebrates

Mollusc

Annelids

Flatworms

Arthropods

Coelenterates

Now let's classify green plants
There are hundreds of thousand of different plants, so we didide them into smaller groups to help us to identify and to study them.
There is more than one way of doing this.

Some plants have a special transport system for food and water called a vascular system. So we call these plants vascular plants.

Plants without a vascular system are called non-vascular plants.

Questions

What is the meaning of the word habitat?
Explain why organisms are adapted to their environment

Cells

2010-11-17T05:47:00.000-08:00

Animals and plants are made of cells. Cells form the basic "building blocks" for living things. Some cells have specialised functions.
Tissues are made from cells of a similar type. Organs are made from tissues, and systems are made from several organs working together.

Cells are very small. They are the basic building blocks of all animals and plants. These photographs show cells seen through a microscope.

Cheek cells

These are cheek cells, seen through a microscope:

Onion cells

These are onion cells, seen through a microscope:

Animal cells usually have an irregular shape, and plant cells usually have a regular shape
Cells are made up of different parts. It is easier to explain what these parts are by using diagrams like the ones below.

Animal cells and plant cells both contain:

cell membrane, cytoplasm, nucleus

Plant cells also contain these parts, not found in animal cells:

chloroplasts, vacuole, cell wall

The table summarises the functions of these parts.

Part	Function	Found in
Cell membrane	Controls what substances can get into and out of the cell.	Plant and animal cells
Cytoplasm	Jelly-like substance, where chemical reactions happen. In plant cells there's a thin lining, whereas in animal cells most of the cell is cytoplasm.	Plant and animal cells
Nucleus	Controls what happens inside the cell. Carries genetic information. In exams don't call the nucleus the 'brain' of the cell. That is not a good description and will not get you marks.	Plant and animal cells
Chloroplast	Where photosynthesis happens – chloroplasts contain a green substance called chlorophyll.	Plant cells only
Vacuole	Contains a liquid called cell sap, which keeps the cell firm.	Plant cells only
Cell wall	Made of a tough substance called cellulose, which supports the cell.	Plant cells only

Humans are multi-cellular animals. That means we are made of lots of cells, not just one cell. The cells in many multi-cellular animals and plants are specialised, so that they can share out the processes of life. They work together like a team to support the different processes in an organism.

Specialised cells

You should be able to work out special features of a cell from a drawing, if you are told what the cell can do. The tables below show examples of some specialised animal and plant cells, with their functions and special features.

Type of animal cell	Function	Special features
Red blood cells	To carry oxygen	Large surface area, for oxygen to pass through Contains haemoglobin, which joins with oxygen
Nerve cells	To carry nerve impulses to different parts of the body	Long Connections at each end Can carry electrical signals
Female reproductive cell (egg cell)	To join with male cell, and then to provide food for the new cell that's been formed	Large Contains lots of cytoplasm
Male reproductive cell (sperm cell)	To reach female cell, and join with it	Long tail for swimming Head for getting into the female cell

Type of plant cell	Function	Special features
Root hair cell	To absorb water and minerals	Large surface area
Leaf cell	To absorb sunlight for photosynthesis	Large surface area Lots of chloroplasts

Tissues

Animal cells and plant cells can form tissues, like muscle tissue. A living tissue is made from a group of cells with a similar structure and function, which all work together to do a particular job. Here are some examples of tissues:

muscle
the lining of the intestine
the lining of the lungs
phloem (tubes that carry dissolved sugar around a plant)
root hair tissue (for plants to take up water and minerals from the soil)

Organs

An organ is made from a group of different tissues, which all work together to do a particular job. Here are some examples of organs:

heart
lung
stomach
brain
leaf
root

Organ systems

An organ system is made from a group of different organs, which all work together to do a particular job. Here are some examples of organ systems:

circulatory system
respiratory system
digestive system
nervous system
reproductive system
leaf canopy

click here to try some questions

source:
http://www.bbc.co.uk/apps/ifl/schools/ks3bitesize/science/quizengine?quiz=cells&templateStyle=science

Microbes & Diseases II

2010-11-15T08:09:00.001-08:00

Protecting ourselves against diseases

Your body has several ways defends itself against micro-organisms.

· Sweat and tears contain an enzyme that kills bacteria.

· Hairs in your nostrils trap micro-organisms and mucus contains enzymes that can kill bacteria.

· Enzymes in saliva can kill bacteria.

· Most bacteria swallowed with food and drinks are killed by acid in the stomach.

But microbes get past these defenses

Tuberculosis (TB) is a serious disease that destroys lung tissue.

TB comes with a bad cough and each time a person with TB cough, they spray little droplets into the air. These droplets contain TB bacteria.

If you are nearby, you can breathe them in.

What happens when you catch a cold

Several different viruses cause colds. When you have a cold and sneeze, you spray several droplets of liquid into the air. Each droplet contains thousands of viruses.

When you first catch a cold, the virus multiplies very quickly. You begin to feel ill, with a runny nose, sore throat and a cough.

Your body starts to fight back the invasion; cold viruses are destroyed and you start to feel better.

How your body destroys microbes

Your blood contains red blood cells and white blood cells. There are two different types of white blood cells.

1. One type of white blood cell engulfs (traps) microbes and destroys them.

2. Another type of white blood cell makes disease-fighting substances called antibodies. These can stop microbes from causing disease.

Each antibody that you make is specific to fighting one type of microbe.

An antibody won’t work against any other type of microbe.

Different microbes need different antibodies. It takes time for your body to make these different antibodies, and you feel ill until you have enough antibodies to destroy the microbes.

Once you have had a disease, your white blood cells have learnt how to make the antibodies. They will be able to make the right ones much more quickly in the future.

If a second attach comes, your body can destroy the microbes before they have time to make you ill. This means you are immune to the disease. You have immunity.

Active immunity

This happens when people make their own antibodies to a disease.

Natural: if you have been infected with a disease, your body made antibodies to destroy it. Your body remembers the disease, and is ready to make antibodies quickly if you were ever infected again.

Artificial: you can be injected with a vaccine containing weakened or dead microbes, or some bits of microbes. The active live microbes are not present, so the vaccine does not make you ill. But your body reacts to the microbes and sets about making antibodies to fight them. It then remembers how to make these antibodies, ready to react if you are ever infected with the disease.

Passive immunity

With passive immunity, people are given ready-made antibodies.

Natural: pregnant women pass on their antibodies to their growing baby through the placenta.

There are also antibodies in breast milk. This gives newborn babies some immunity from microbial infections.

Artificial: antibodies are made outside the body, for example in the laboratory. These antibodies are injected into people and animals to give protection from fast-acting microbes. An example is the anti-tetanus vaccine. You may be injected with this if you have a deep or dirty wound where tetanus bacteria may grow. Your body may not make its own antibodies fast enough to fight.

Immunisation is a very effective way of preventing an epidemic, when a disease spreads through the population.

Vaccines only work if lots of people are immunised.

Microbes & Diseases

2010-11-10T04:12:00.000-08:00

Microorganisms

Introduction

If you can only see a living thing with a microscope, that means it is a microorganism. These are found everywhere.
Some of them, like yeast are helpful. And some of them are harmful and disease causing, like bacteria. It is important to know how to avoid spreading the bad ones!

This section includes:

What are microorganisms?
Harmful microorganisms
How to avoid spreading harmful microorganisms
Helpful microorganisms

What are microorganisms?
Microorganisms are very tiny living things. They are so small that you need a microscope to see them.

microscope

Microorganisms are all around us, in the air, in the soil, in our bodies and in water. Some microorganisms are harmful to us, but others are helpful to us.

There are three types of microorganism:

viruses
bacteria
fungi

Viruses
Viruses can only reproduce inside a living cell.
Average size: 0.0001mm
Structure: A strand of genetic material wrapped in a protein coat.
Uses: To kill pest animals
Diseases: Common cold, influenza (flu), measles, AIDS, yellow fever, rabies,

Bacteria
Most bacteria live in water, soil and decaying material.
Average size: 0.001mm

Structure: Bacteria are single-celled with a strong cell wall. their genetic material is not in a nucleus.

Uses: To make yoghurt, cheese and vinegar.
Diseases:Typhoid, cholera, food poisoning.

bacteria

Fungi
Some fungi are microorganisms, for example yeast and mould. Yeast is made of single cells that reproduce by budding off new cells. Yeast cells are larger than viruses.

yeast

Moulds are fine threads that grow on rotting food; they also give blue cheese its colour and flavour.

blue cheese

Fungi can be helpful: we use yeast to make bread, beer and wine and mould to make antibiotics. they can also be harmful; fungi cause athlete's foot and ringworm.