Chemistry Year 9 Matter Year 9 Science 2013

The History of Atomic Theory All matter is made up of tiny particles called atoms An atom is the smallest neutral particle that makes up matter. Scientists and philosophers have guessed that all matter is made up of building blocks for a very long time. Discovery of the actual structure of the atom has only been in relatively recent times however. The History of Atomic Theory Year 9 Science 2013

All matter is made up of tiny particles called atoms John Dalton (1766–1844) was a British chemist and physicist. In 1803 he announced his atomic theory. My Theory States: All Elements are made up off tiny particles called atoms. Atoms of a given element are alike Atoms of different elements are different Chemical changes take place when atoms link up with or separate from one another Atoms are not created or destroyed by chemical change Year 9 Science 2013

All matter is made up of tiny particles called atoms Sir Joseph John Thomson, who had discovered (1897) the electron, and came up with a model of the atom known as the plum-pudding model. Year 9 Science 2013

All matter is made up of tiny particles called atoms Ernest Rutherford was a New Zealand Scientist. In 1911 he announced his new atomic model based on what he observed from his famous ‘gold foil’ experiment. Year 9 Science 2013

Ernest Rutherford’s Gold Foil experiment All matter is made up of tiny particles called atoms Ernest Rutherford’s Gold Foil experiment “ It was the most incredible event that has ever happened to me in my life. It was almost as incredible as if you fired a cannon-ball at a piece of tissue and it came back and hit you.” - Ernest Rutherford Year 9 Science 2013

Atoms have a particular structure – protons, electrons and neutrons Atoms have a central nucleus. The nucleus contains protons (p) and neutrons (n). Electrons (e) orbit the nucleus, arranged in shells or energy levels. Electron -ve Nucleus Neutron N P N P N N P Proton +ve P P P N N This is known as the Bohr model. Shell 1 Shell 2 Year 9 Science 2013

Atoms have a particular structure – protons, electrons and neutrons Atoms are very small. Very special microscopes are required to see them. Many billions of atoms are required to produce this full stop. Year 9 Science 2013

Atoms have equal number of protons and electrons Protons are positively charged; electrons are negatively charged; neutrons have o electrical charge. Atoms have no overall charge because the number of protons = number of electrons. Summary All matter is made up of atoms. Atoms consist of protons, neutrons and electrons. The charges of protons and electrons are equal and opposite. Year 9 Science 2013

Matter consisting of only one type of particle (atom) are elements Pure substances made up of only one type of atom are called elements. There are 106 known elements and therefore 106 different types of atoms. Elements can be grouped into metals and non-metals. Most elements are found in their solid form on earth but some are also found as liquids and gases. Element Metal Solid Liquid Non-Metal Gas Iron Mercury Sulfur Bromine Oxygen Year 9 Science 2013

Atoms can exist in different arrangements There are approximately 100 different elements but many millions of substances. Most matter around us is made up of combinations of elements. If different elements are just jumbled up then they form a mixture. If different elements have chemically reacted together and joined then they form a compound. A molecule forms when atoms join together – either the same to form a molecule of an element or different to form a molecule of a compound. Atoms of an element Molecules of an element Molecules of a compound Mixture of elements and a compound Year 9 Science 2013

Matter consisting of only one type of particle (atom) are elements Most elements are metals. They are mostly all solids and shiny that can be bent into many shapes. They can conduct electricity and heat. Iron Gold Copper Sodium Tin Silver Magnesium Year 9 Science 2013

Matter consisting of only one type of particle (atom) are elements Non-metal elements are not shiny and can’t be bent. They usually cannot conduct electricity. Carbon Sulfur Oxygen Neon Phosphorus Year 9 Science 2013

Each different type of element has a different number of protons in its atoms All Boron atoms have 5 protons in their nucleus. All Carbon atoms have 6 protons in their nucleus. Year 9 Science 2013

Each element is named and has a specific symbol. Elements consist of only one type of atom. Each element can be represented by a chemical symbol. Year 9 Science 2013

Understand there is a correct way of writing element symbols. >Most symbols are one or two letters, formed from the name of the element. e.g. Hydrogen H, or Helium He. >The first letter of the symbol is always a capital letter. Any other letters are lower case. e.g. Helium is He not HE >If the symbols are not based on a elements English name then it is most likely to be based on it’s Latin name, the original language of Science. Year 9 Science 2013

Understand that elements are arranged on the periodic table according to their atomic number. Each element has an atomic number which tells us how many protons are contained inside each atoms nucleus. This number of protons is matched by an equal number of electrons which move around the nucleus. The periodic table starts with Hydrogen (H) Atomic number 1 and ends with elements that have over 100 protons such as Copernicium (Cn) Atomic number 112.

Year 9 Science 2013

Understand the more protons an atom has the further down the table it is. Year 9 Science 2013

Learn that Groups of elements on the periodic table have common physical and chemical properties Elements that are in the same group show similar types of chemical and physical properties. Their atoms chemically react the same way because their electrons in the outside shell in the atoms are arranged the same way. Group 1 Metals The elements in a group also have similar physical properties because of the way the atoms join together and are arranged. Group 17 Non-Metals Year 9 Science 2013

Groups are numbered vertical columns and periods are horizontal rows The columns (downwards) of a periodic table are called groups. The rows (across) of a periodic table are called periods. Elements in the same group all have the same number of electrons in their outer (or valence) shells. Elements in the same period all have the same number of shells of electrons in their atoms Year 9 Science 2013

Metals are placed on the left hand side and non-metals are placed on the right hand side of the periodic table Elements can be classified as metals or non-metals. A few elements are called semi-metals or metaloids (e.g. boron and silicon), because they show some, but not all, of the properties of metals.

The groups of metals and non-metals have specific defining physical properties >Lustre (shiny) >good conductor >High density >High melting point >Malleable (can shape into sheets) >Ductile (can shape into wires) Semi-Metals >Solids >Can be shiny or dull >Ductile and malleable >Conduct heat and energy better than Non Metals but not as good as metals Non-Metals >No lustre >Poor conductor >Brittle >Not ductile >Low density >Low melting point 23

Matter exists in different states – solid, liquid and gases Gases, liquids and solids can be made up of atoms, molecules, and/or ions, but the behaviours of these particles differ in the three states. Solids remain in a fixed shape – the particles vibrate but remain tightly bonded to each other. Liquids take the shape of the container – the particles can move past each other but are still bonded. Gases fill any container they are in – the particles move fast and are not bonded to each other Year 9 Science 2013

Matter can change from one state to another condensation Gas evaporating sublimation deposition Liquid Freezing Solid If energy is absorbed or released the particles which make up the matter can change state. A change of state is a physical reaction and it is reversible. Melting Year 9 Science 2013

Characteristics of Gases, Liquids and Solids Particles are arranged and move differently in solids, liquids and gases Characteristics of Gases, Liquids and Solids gas liquid solid assumes the shape and volume of its container particles can move past one another assumes the shape of the part of the container which it occupies particles can move/slide past one another retains a fixed volume and shape rigid - particles locked into place compressible lots of free space between particles not easily compressible little free space between particles flows easily particles can move/slide past one another does not flow easily rigid - particles cannot move/slide past one another Year 9 Science 2013 Year 9 Science 2013 26 26 SJ Gaze

Particles are arranged and move differently in solids, liquids and gases Solid particles are packed closely and only vibrate in a fixed position. Liquid particles are also packed closely but the particles move around more. Gas particles have a lot of space between them and move around quickly. Gas Liquid Solid Year 9 Science 2012 Year 9 Science 2013 27

Particles are arranged and move differently in solids, liquids and gases The movement of particles in any state is determined by three factors: How strong the bonds are between the particles, how much energy (kinetic) the particles contain and the mass of the particles. Particles move faster when: they have less mass, have weaker bonds between particles and have more energy. Particles move slower when: they have more mass, have stronger bonds between particles and have less energy. Year 9 Science 2013

The particles of different states have different kinetic energy levels Kinetic energy causes particles to move. The more kinetic energy a particle has the faster it moves. Kinetic energy can be added to a particle by adding heat energy (and heats up). The heat energy is then transformed into the kinetic energy. Kinetic energy can also be lost from a particle, which slows it down, when it changes back into heat energy and is lost (and cools). Year 9 Science 2013