Year 9 Science: Chemistry Revision 2012

Year 9 Science: Chemistry Revision 2012 
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What subatomic particles (Pro, Neu, Elec) are found in atoms; their properties and location
Protons: positive, heavier, located in the nucleus Neutrons: neutral, heavier, located in the nucleusElectrons: negative, lighter, located in shells surrounding the nucleus
· Terms used to describe atoms – mass number, atomic number ·

- Symbol- how many protons, electrons and neutrons- atomic and mass no.- non-metal/metalloid/metal?
· Symbol used to show mass number and atomic number·

· What is an element (examples)? · What is a molecule (examples)? · What is a mixture (examples)?
element - the basic building of all matter (e.g. carbon)molecule - a group of atoms bonded together (e.g. methane) mixture - can be separated by techniques such as filtration or evaporation since it is made of different elements or compounds simply thrown together. (e.g. cold milo)
· What criteria did Mendeleev use in putting together his periodic table?

In 1869 Russian chemist Dmitri Ivanovich Mendeleevarranged the known elements in order of atomic mass,putting the similar elements into vertical columns. he left gaps for undiscovered elements
· Where would you find elements with similar properties on the periodic table?
in the same groups
· The layout of the periodic table – periods, groups, transition elements, lanthanides, actinides

How are electrons arranged in atoms – shells, electron configuration
Electrons are arranged on shells that orbit around the nucleus. the electrons are arranged in the shells like so: 1st shell 2nd shell 3rd shell 4th shell Max of 2e- Max of 8e- Max of 18 e- Max of 32e- the atom prefer to have 8 electrons on the outer shell.
· Relationship of electron configuration to the periodic table
· What is special about Group VIII properties and electron configuration?
Group VIII are the noble gases.
· Properties of metals – location on periodic table. · Properties of non-metals – location on periodic table.
metals - left side, shiny, ductile, good heat conductors and electricity
non-metals - right side, non-shiny, dull, brittle, poor conductors, good insulators

What is unusual about hydrogen compared to other Group I elements.
A hydrogen atom only has one electron. It can emptyits K electron shell by losing this electron to becomethe hydrogen ion H+, or it can gain another electronto become the hydride ion H– with the same electron configuration as He. In this way it can act like a Group I or Group VII element, depending on what it comes into contact with.
What is unusual about helium compared to other Group VIII elements.

A helium atom has 2electrons that fill its onlyshell. Helium therefore has similar properties to the noble gases of Group VIII. It could be placed in Group II but is placed in Group VIII because of similar properties to noble gases.
What are metalloids (examples)?
The metalloids (sometimes called semi-metals) actlike non-metals in most ways. They do, however, have some properties that are metallic: most importantly, they can conduct electricity.
· Location of the noble gases, halogens, alkali metals, alkaline earths, Group IV and transition metals on the periodic table (and examples)

noble gases - group VIII (e.g. neon)halogens - group VII (e.g. fluorine)alkali metals - Group I (e.g. lithium)alkaline earths - Group II (e.g. beryllium)Group IV - group 4 (e.g. carbon) transition metals - center of periodic table (e.g. zinc)
Trends within each group


· Ions – simple ions and polyatomic ions

Simple - Ions are charged particles that have an unequal number of protons and electrons.
Polyatomic - Not all ions are formed from single atoms. Ions that are made up of more than one atom are called polyatomic ions.
Very basic Ionic Compounds·
Positive ions attract negative ions. This attraction,called electrostatic attraction, forms an ionic bond.Ionic compounds are called salts.
Diatomic molecules are very common. Mostof the air we breathe is made up of the diatomicmolecules oxygen, O2, and nitrogen, N2.
Solutions – solvent, solute,
A solution is a liquid with something dissolved in it. the solute is the thing that is dissolved. the solvent is the liquid.


· Physical change,

Perhaps it’s easiest to start with things that aredefinitely not chemical changes. When waterturns to ice, or an aluminium can is squashed, aphysical change has taken place.

Chemical Change,

A chemical change is one where anew substance is formed. Sometimeschemical change is very obvious:exploding a stick of dynamiteproduces obvious new substances,as does burning petrol in a carengine.

Signs of Chemical change (basic signs)

• a permanent colour change occurs, e.g. a carrusting• a gas is given off, e.g. a Berocca tablet dissolving• there is a change in temperature, indicating thatenergy has been produced or absorbed,e.g. gas burns in a Bunsen burner• a precipitate (solid) forms when twosolutions are mixed• one metal deposits on another
· What is an acid,
- have a sour taste- turn blue litmus red- conduct electricity when mixed with water to make an aqueous solution - can neutralise a base

What is a base·

- opposites of acids- neutralise acids by reacting with them to produce water and other substances - strong bases are capable of burning - alkalies are the bases that dissolve in water - have a bitter taste - turn red litmus blue
talk about the pH scale

- the pH is used to compare the relative acidity of substances in solution- pH scale (at 25 degrees C) goes from approximately 0 - 14

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