section 10 chemistry

• Chemicals on the left hand side of an equation are reactants. Chemicals on the right hand side of an equation are products.
• There are 2 types of equations: Word equations (e.g. Methane + Oxygen -- Carbon dioxide + water). And symbol equations (e.g. 2Mg + O2 -- 2MgO)
• Common Chemical formulas: Water - H2O Carbon dioxide - CO2 Chlorine - CL2 Ammonia - NH3 Hydrogen - H2 Oxygen - O2
• Ions ending in -ate are negative ions containing oxygen and at least one other element. Ions ending in -ide are negative ions only containing one element (except hydroxide ions)
• A hazard is anything that could cause harm or damage. A risk for a hazard is how likely it is that someone will be harmed by it.
• Hazard symbols: Highly flammable, Harmful, corrosive (destroys materials), Toxic, Environmental hazard, oxidising.
• Protons are positively charged. Neutrons are neutral. And electrons are negatively charged.
• The nucleus of an atom contains protons and neutrons. it has a positive charge because of the protons.
• The atomic number tells you how many protons an atom has. The mass number is the total number of protons and neutrons in an atom.
• Isotopes are elements that have the same number of protons but a different number of neutrons. They have the same atomic number but different mass numbers.
• Negative ions (anions) form when atoms gain electrons. Positive ions (cations) Form when atoms loose electrons.
• There are strong electrostatic forces of attraction between oppositely charged ions. These are ionic bonds
• Ionic compounds have high melting points and boiling points. Many ionic compounds can dissolve in water. Solid ionic compounds don't conduct electricity. When the compound melts it can carry an electric charge.
• a covalent bond is formed when two atoms share a pair of electrons. atoms form covalent bonds to get a full outer shell of electrons.
• A single covalent bond is where a single pair of electrons are shared.
• A double covalent bond is where two pairs of electrons are shared.
• forces between molecules are called intramolecular forces. They are very weak.
• Most molecular substances are liquids or gases at room temperature. Molecular compounds don't conduct electricity because they don't have electrons or ions that can move through the substance.
• Some simple molecules are soluble, and some aren't soluble.
• Giant covalent structures have strong covalent bonds. They have high melting and boiling points. They can't conduct electricity because they don't have particles that are free to move. They aren't soluble in water.
• Example of a giant covalent structure made of carbon atoms: Diamond. Has carbon atoms that form four covalent bonds. This makes diamond really hard. Diamond has a high melting point. It doesn't conduct electricity.
• Another example of a giant covalent structure made of carbon atoms: Graphite. Carbon atoms only form three covalent bonds which makes sheets of carbon atoms. They're aren't any bonds between the sheets which makes a weak attraction. This means they're free to move. This makes graphite soft and slippery. It's got a high melting point. It conducts electricity. Often used to make elctrodes.
• Polymers are molecules that contain long chains of covalently bonded carbon atoms. Polymers are formed when small molecules called monomers join together.
• Metals have a giant structure. The electrons in the outer shell of the metal atoms are free to move between the layers of metal ions (They are delocalised). There are strong forces of electrostatic attraction between the positive metal ions and the negative electrons. This is called metallic bonding.
• Substances with metallic bonds have very high melting and boiling points. Metals are shiny solids at room temperature. They can't dissolve in water. They're more dense than non-metals. They're malleable. They can conduct electricity.
• Non-metals don't have metallic bonding which means they have different physical properties. They have low melting and boiling points. They don't conduct electricity.
• Metals and non-metals also have different chemical properties. Non-metals usually have more than half of their outer shell filled this means they gain electrons. Metals usually have less than half of their outer shell filled which means they loose electrons.
• During a chemical reaction no atoms are created or destroyed. Instead atoms in reactants are rearranged to make products. This means there are the same number and types of atoms on each side of a reaction equation so the total mass of the reactants is the same as the total mass of the products. This is the law of conservation of mass