Advanced Chemistry

Question 1

Chemical Reaction

Answer 1

A process that involves rearrangement of the molecular or ionic structure of a substance, as distinct from a change in physical form or a nuclear reaction.

Question 2

Exothermic

Answer 2

When molecule a releases heat.

Question 3

Endothermic

Answer 3

When a molecule absorbs heat.

Question 4

Precipitate

Answer 4

To cause a substance to be deposited in solid form from a solution.

Question 5

Reactant

Answer 5

A substance that takes part in and undergoes change during a reaction.

Question 6

Product

Answer 6

A substance that is formed as the result of a chemical reaction.

Question 7

State

Answer 7

A physical condition as regards internal or molecular form or structure.

Question 8

Aqueous

Answer 8

Containing water.

Question 9

Coefficient

Answer 9

A numerical or constant quantity placed before and multiplying the variable in an algebraic expression (e.g. 4 in 4x y).

Question 10

Acids

Answer 10

Acids are very reactive. They: - React with metals - Taste sour - Conduct electricity - Solutions with a pH below 7 are considered acidic. - When put into a solution, acid particles separate into hydrogen ions. If most of the particles separate into hydrogen ions, the acid is strong. If most don’t, then the acid is weak.

Question 11

Bases

Answer 11

Bases: - React with acids - Taste bitter - Are caustic (cause burns) - When put into a solution, base particles separate into hydroxide ions. If most of the particles separate into hydroxide ions, the base is strong. If most don’t, then the base is weak.

Question 12

Indicators

Answer 12

pH indicators come in various forms and show the rough or exact pH of a substance depending on the form of indicator. - Universal indicators show the exact pH level by turning a specific colour for each pH level. - Litmus paper is the most simple indicator. It turns blue if a solution is acidic and turns red if the solution is a base. - Other indicators change colour at a particular pH. For example, thymol blue has three different colours. It is red below pH 1.2−2.8, blue above pH 8.0−9.6, and yellow in between.

Question 13

Acid-Metal Reactions

Answer 13

Acids react with metals to create a salt, and hydrogen gas. This is written: Acid + Metal → Salt + Hydrogen gas (H2​) We write hydrogen gas as H2​, this is its chemical formula.

Question 14

Salts

Answer 14

When we say salt, we mean a type of chemical called salts. It does not mean just sodium chloride (what we call table salt) - that is just one kind of salt. Salts are made up of a metal ion and a non-metal ion. Other examples of salt include potassium chloride, calcium chloride, and copper sulfate. Salts are named by the acid and metal ions which create them. The metal provides the first part of the name, and the acid provides the second. So for example, Hydrochloric acid + Copper → Copper Chloride + Hydrogen The salt here is copper chloride (below), which takes copper from the metal and chloride from the acid.

Question 15

Neutralisation Reactions

Answer 15

Neutralisation reactions are where bases are added to acids to make the pH a specific number. This could be because different animals and plants need a specific pH level. Adding the base neutralises the acid. Hydroxides, oxides, and carbonates can all be added to acids to neutralise them.

Here are the different reactions which happen with each base:

acid + hydroxide → salt + water

acid + oxide → salt + water

acid + carbonate → salt + water + carbon dioxide

Question 16

Endothemic & Exothermic Reactions

Answer 16

Endothermic and exothermic reactions are related to heat transfer. Endothermic reactions occur when a system (a thing) absorbs heat from the surrounding area. Exothermic reactions occure when a system releases heat into the surrounding areas.

When the products have more energy than the reactants, we have an endothermic reaction. These take energy away from their surroundings so that they can happen.

When the reactants have more energy than the products, we have an exothermic reaction. These release energy into their surroundings as they happen.

Question 17

Endothermic & Exothermic Reactions - Continued

Answer 17

Changing states can also be called endothermic or exothermic.

When a solid changes to a liquid, or a liquid changes to a gas, it is endothermic. This is because heat energy is being put into the substance in order to boil or melt it.

When a gas changes to a liquid, or a liquid changes to a solid, it is exothermic. This is because heat is being removed from the substance in order to condense or freeze it.

Question 18

Combustion Reactions

Answer 18

Combustion is an exothermic reaction. A lot of energy is released in the form of heat as the combusting substance burns or explodes. Combustion is a reaction which occurs when a substance reacts with oxygen. Oxygen is always required for combustion reactions, which is why they can be stopped by removing the oxygen source.

Most combustion reactions look like this:

Fuel + Oxygen → Carbon Dioxide + Water

Question 19

Incomplete Combustion Reactions

Answer 19

Incomplete combustion reactions are when a combustion reaction takes places with less oxygen. This means that the substance does not combust properly. Incomplete combustion reactions burn cooler and produce more carbon.

For example, this is what an incomplete methane combustion looks like:

Methane + Oxygen → Carbon + Water

If it was complete, it would be carbon dioxide instead of carbon.

Question 20

Oxidation Reactions

Answer 20

Oxidation reactions are when electrons are moved from one electron to the other. This often happens when mixing oxygen and a metal.

Question 21

Corrosion

Answer 21

Corrosion is one form of oxidising. It is when oxygen reacts with metal, air and water. This forms metal oxides, creating rust(iron & steel), tarnishes (silver) and verdigris (verdigris).

Rust - 4Fe +3O2​→2Fe2​O3​

Tarnish - 2Ag + H2​S → Ag2​S + H2​

Verdigris - 2Cu + H2​O + O2​+ CO2​→ CuCO3​+ Cu(OH)2​

Question 22

Chemical & Physical Changes

Answer 22

A physical change is when a substance changes its appearance and not its chemical makeup. Physical changes are reversible.

A chemical change is when reactants combine to form new products. These products have different physical and chemical properties to the reactants that formed them.

Question 23

Combination & Decomposition Reactions

Answer 23

Combination reactions (also known as synthesis reactions) is when multiple reactants combine to form a single product.

Decomposition reactions is when a single reactant breaks apart to form multiple products

Question 24

Precipitation Reactions

Answer 24

Precipitation reactions occur when multiple soluble reactants combine to form insoluble products. During a precipitation reaction, the solution will go from clear to cloudy.

The solubility table tells us if a specific ionic compound is soluble or not.

Question 25

Types of Radiation Continued

Answer 25

Alpha Particles Can be Stopped by a:

• Few centimetres of air.
• Thin piece of paper.

Beta Particles Can be Stopped by a:

• Few metres of air.
• Aluminium.

Gamma Rays Can be Stopped by a:

• Thick layer of lead.
• Thick layer of concrete.

Question 26

Types of Radiation

Answer 26

Alpha Particles

• Two neutrons and two protons.
• Electrical charge of +2.
• Larger than beta particles and are slower.
• Low penetrating ability.

Beta Particles

• One electron.
• Electrical charge of -1.
• Smaller than alpha particles and faster.
• Moderate penetrating ability.

Gamma Rays

• Wave of electromagnetic radiation.
• Electrical charge of 0.
• Not particles, very fast and a high penetrating ability.