Matter
Matter is anything that has mass and takes up space.
Mass is a property related to weight, but is not the same.
Think about the fruit floating in front of the astronaut. They are weightless, but they still have mass. If one of them was really fake - say, made out of heavy metal but painted to look like an apple, he could still tell this if he tried to move it. It would be harder to start and stop moving - a property called Inertia. It is mass that gives objects their inertia. The formal definition of mass is that it is the amount of matter in an object. The units of mass are kilograms.
Every element on the periodic table has a name, a number and a symbol.
the name can be different in different languages e.g. element number 11 is sodium in English and natrium in French; element number 1 is wasserstoff in German but hydrogen in English.
the number is unique to the element (it is the number of protons in the atom)
the symbol has one or two letters, which is the same in every language. If the symbol is two letters, the first letter is always uppercase and the second lowercase. Single letters are uppercase only. Using the case incorrectly is not allowed.
Although the symbol is often based on the English name e.g. O for oxygen, sometimes it is based on another language. If you were a student in Germany, Na for natrium, which we call sodium, makes perfect sense but O seems to be a strange symbol for the element you call sauerstoff.
The first 20 elements
In Year 8 you need to learn the names, symbols and something about each of the first 20 elements.
Below is a shortened 'periodic table' of the first twenty elements and a quick summary about each one.
Notes about the First 20
- the links are to Simple Wikipedia, which is a very useful resource for younger students.
Hydrogen: this is the most common element in the Universe. 98% of the atoms in the universe are hydrogen, but nearly all these atoms are found in space as stars and gas between the stars. It is the lightest element. Hydrogen doesn't occur by itself on Earth but is mostly combined with oxygen to make water. Hydrogen gas is very flammable, a property that contributed to the Hindenburg disaster.
Helium: is the second lightest gas. It is named after the Greek name for the Sun (Helios) because it was first detected from the light it makes when heated up in the Sun. Most stars, including our Sun, get their energy from converting hydrogen to helium using nuclear fusion. This is also how a hydrogen bomb works. Helium for balloons and other uses comes from natural gas, where it is formed by the breakdown of radioactive minerals in the surrounding rocks. As this helium runs out you can expect the price of helium to increase hugely. Helium is as light as hydrogen, but it inert. It can't burn or explode. Its most important use is to cool the world's most powerful magnets, such as in hospital MRI scanners.
Lithium: this is the lightest metal. However, the metals in the left hand column of the periodic table all react violently with water so are not used as metals by themselves. Lithium is becoming valuable today because of its use in rechargeable batteries. The metals in the left column are called the alkali metals.
Beryllium: a light but rare metal found in the mineral beryl (emerald). It has a range of high tech uses by is very expensive.
Boron is a 'trace element' essential for life. It forms an acid, boric acid, which is used as an ant killer. When you neutralise this acid you get borax. Borax can be melted to make a type of glass, or to turn certain glues and gums into a rubbery slime.
Carbon is essential for all living things. Most of the molecules in your body contain carbon. Carbon compounds include carbohydrates, proteins, fats, plastics, oil and natural gas. Carbon occurs naturally as an element as the minerals diamond and graphite.
Nitrogen gas makes up 78% of the atmosphere. However, nearly all nitrogen on Earth is found in the atmosphere or as biomass (i.e. in living things) so it is quite a rare element overall. Nitrogen is quite common on gas giant planets such as Jupiter or Neptune. On those planets it forms either nitrogen gas (or liquid) or ammonia (gas, liquid or solid).
Oxygen is the commonest element on Earth. However, 99.9% of the Earth's oxygen is combined with other elements in the form of minerals or water. The tiny fraction of oxygen occurring as an element in the atmosphere is essential for most living things for respiration.
Fluorine is much less common than its cousin chlorine. It occurs in the minerals fluorite and apatite. Your teeth contain crystals of apatite, which is why fluorine compounds are added to drinking water. Without exposure to fluorine, the apatite in your teeth changes to a softer type which forms cavities more easily. Fluorine compounds are used for non-stick and water-resistant plastics and certain drugs. The possum poison 1080 is made by modifying sodium acetate (found in salt'n'vinegar chips) by replacing one hydrogen atom with a fluorine atom.
Neon is a light gas similar to (but not as light as) helium. The red tube lights you see above the meat display in a butcher contain neon gas and are called 'neon lights' . Most "neon lights" which are other colours than an orange-red colour actually contain neon's similar and cheaper cousin, argon.
Sodium is found combined with chlorine in salt. It is also a part of many common minerals. Your body needs a certain amount of salt, and if you lose too much (e.g. by sweating a lot) you can get cramps.
Magnesium is a light metal that burns with a bright white flame. It is the fourth most common element on Earth, but all magnesium is found combined with other elements in minerals such as olivine. Magnesium sulfate is called Epsom Salts. It can be added to bath water to ease aching muscles.
Aluminium is a light metal somewhat stronger and a bit less prone to burning than magnesium. Aluminium is harder to refine from minerals than magnesium, so before the modern method of refining it was discovered it was even more expensive than gold. Aluminium is the third most abundant element in the Earth's crust but is less common in the mantle and core, which make up most of the Earth. Aluminium metal has hundreds of uses and is the second most widely used metal (after iron and steel).
Silicon is the second most abundant element on Earth and is found in most minerals. Sand is mostly silicon dioxide (quartz). Ninety percent of rocks contain silicon and oxygen as their main ingredients.
Phosphorus is essential for living things. Plants often don't get enough phosphorus from natural sources, so phosphate fertilisers can make them grow better. Topdressing of phosphate by plane in NZ hill country was what made sheep farming on this land economic.
Sulfur occurs around volcanoes as a yellow mineral. It forms two gases, hydrogen sulfide and sulfur dioxide, which give Rotorua its distinctive smell. Most of our sulfur is extracted from oil. Sulfur and its compunds have many uses; for example, combined with calcium and oxygen it makes up the plasterboard that is lining your house.
Chlorine is the most common element in the family of halogens (which include fluorine, bromine and iodine). All halogens occur as compounds in sea water. Common or table salt is a compound of sodium and chlorine. "Pool chlorine" is actually a compound which breaks down to produce small amounts of the element chlorine. Chlorine as an element is extremely poisonous, but tiny amounts of it in water can kill harmful microbes without harming people. Chlorine reacts very quickly with vitamin C, so if you have to drink water that tastes strongly of chlorine adding a source of vitamin C (such as lemon juice or a vitamin C tablet) will quite quickly get rid of the chlorine smell and taste.
Argon is an 'inert' gas used in light bulbs to stop the hot wire burning up, and in other places where it prevents burning or chemical reactions.
Potassium is very similar to sodium and never occurs as an element, only as compounds. Plants need potassium, particularly when producing fruit, so adding potassium compound fertilisers can improve the size and taste of fruit such as feijoa and banana. You need a small amount of potassium and usually get enough in your diet. Too much can give you an irregular heartbeat.
Calcium is the fifth most abundant element in the Earth's crust and is found in many minerals. Your body also makes these minerals as a part of bones and teeth. For this reason, you need some calcium compounds in your diet. The best source of these is dairy products.