1. Here let's discuss the difference between atoms, elements, compounds and mixtures. First let's discuss element : Element is the basic substance that can't be simplified and it consists of only one kind of atom. Element cannot be broken down into a simpler type of matter by either physical or chemical means. Notice that element can exist as either atoms like Fe (iron atom) or molecules, for example N 2 (nitrogen molecule). Now go back to atom. Atom is the smallest amount of an element. Just like what we mention, Fe (iron atom), K (potassium atom). Molecule is two or more atoms that are chemically joined together by a covalent bond. For example, N 2 (nitrogen molecule), Cl 2 (chlorine molecule).

2. Now let's talk about compounds. A compound consists of atoms of two or more different elements bound together, and can be broken down into a simpler type of matter by chemical means but not by physical means. Compound has properties that are different from its component elements, and always contains the same ratio of its component atoms. For example, H 2 O water molecule is consisting of H (hydrogen) and O (oxygen) atoms in 2:1 ratio, and H 2 O has properties that are different from its component elements H and O, like water is liquid in room temperature while hydrogen and oxygen are gas under room temperature.

3. Last but not the least let's talk about mixture. Mixture consists of two or more different elements and / or compounds PHYSICALLY intermingled, can be separated into its components by PHYSICAL means, and often has the properties of its components. Notice that I capitalize PHYSICAL and PHYSICALLY, because mixture is not about chemical reactions, it's just physical! For example you mix apple juice with orange juice, then that is a mixture. and it has the properties of its components, it will taste like apple juice and orange juice at the same time. It's not easy to separate them but possible, so this is not a perfect example here. Another better example is sand and magnetized powders. You mix them and you have a mixture. But you can separate them physically using a magnet

4. Relative atomic mass : the average mass of an atom of an element relative to 1/12 the mass of a carbon-12 atom. Relative molecular mass : the average mass of a molecule of an element relative to 1/12 the mass of a carbon-12 atom. Relative isotopic mass : The mass of an atom of that isotope relative to 1/12 th mass of Carbon-12 atom Isotopes are elements which have same number of protons but different number of neutrons

5. Relative formula mass :sum of all relative atomic masses of all the atoms in the chemical formula In covalent compounds, that are made up of molecules, this is referred as relative molecular mass Mole : the amount of any substance containing the same number of identical entities as there are in exactly 12 g of the carbon-12 isotope.

6. Hazard : Substance that can cause harm Risk : Chance that harm will cause by result of using that substance or procedure Precautions : 1- Wear gloves (If acid or alkali used as acids and alkalis are corrosive) 2- A fume cupboard should be used wherever possible when carrying out experiments with organic compounds as toxic fumes are produced 3- Wear masks Hazard of hydrogen : Hydrogen is flammable Hazard of acid/alkali : They are corrosive hazard that with alkanes is that they are flammable.

7. Measuring pH : What we use: -pH meter -Litmus (paper / solution) Why we use:  Measuring acidity or basicity  Acid or alkali has been added exess or not Metal carbonate : example sodium carbonate Reacts with acid to form bubbles

8. Parts per milion  3.13 ppm means (( 3.13/10^6 ) * 100) %  2g of Co2 pollution in 1.5 million grams of solution there will be: (2/1500000) *10^6 = 1.3ppm

9. Collecting Gases

10. Precipitation

11. Making standard solution

12. Acid and Carbonate reactions

13. + Acid Acid and Carbonate reactions

14. 1 - Filter to remove impurities 2 - *Boil / heat / evaporate to reduce the volume of water 3 - Cool / set aside / leave to allow crystals to form 4 - Filter or pick out / remove / take out crystals (to separate) 5 - Wash with a little/cold water 6 - Place between filter papers / dab with paper towel / use dessicator (to dry) Crystallization