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Notes for science-

An atom is the smallest piece of matter that can take part in a chemical reaction.

An element is the Purest form of a substance made up of one element.

A compound is 2 or more different elements chemically combined together.

A molecule is 2 or more Elements that are chemically combined together. Molecules can be the same or different elements that are chemically combined/bonded.

A chemical change produces a new substance. Chemical reactions are not easily reversible. Chemical reactions make the atoms go into different arrangements. Examples of chemical reactions are when wax is burnt.

A physical change is when a reaction does not create a new substance. A physical change is reversible. A physical change does not change the arrangement of the atoms. An example of a physical change is when ice melts into water.

An experiment could be making an ice lantern. Put a candle in a bowl full of water, and freeze it. Then, take it out of the freezer and light up the candle. This will show both a physical and chemical change.

Remember-

Chromatography is a technique to separate colours which have different solubility levels.

Filtrations separates the solids from a mixture.

Evaporation separates the solvent from a liquid.

Distillation separates 2 solvents that have different evaporation temperatures.

Atoms join together by electrostatic attractions called bonds. When they do they form molecules. There is a special type of molecule called a compound. For example, methane is the name of a molecule (and a compound) that has one atom of the element Carbon chemically joined with 4 atoms of the element hydrogen. If you remember the earlier Chemistry in year 7 Chemists used a special short hand called a Chemical Formula. For methane we write 1 times Carbon (C) and 4 times Hydrogen (H). Simplify that and you get C H 4.

Types of reactions include Hydrogen + Oxygen, which creates Water. Iron + oxygen creates Iron oxide. Potassium + water creates Potassium Hydroxide + Hydrogen. Ethanol + Oxygen creates Carbon dioxide + Water.

the conservation of mass means keeping things the same. For example, the mass of a reactant (21 grams and 14 grams) leads to the result of around 35 grams. 21+14=35 grams. Meaning, the total mass of reactants is equal to the total mass of said product.

When writing balanced equations, We can also show what type of matter the thing is using signs that represent the state of matter. The sign of a solid is (s) a gas (g) and a liquid (l). There is another sign (aq) meaning that it is dissolved in water.

Gas tests include putting magnesium ribbon in hydrochloric acid acid to create Hydrogen, Limewater reacting with copper carbonate that was heated up to create carbon dioxide, and Using a glowing stick to test for oxygen from hydrogen peroxide mixed with manganese dioxide ( this helps the hydrogen peroxide decompose faster- it is a catalyst.)