Unit 19: Chemical Reactions

What is an acid?

Proton (H ion) donor, reacts with a base to form salt and water

What is a base?

Proton (H ion) acceptor, reacts with acid to form salt and water

What is an alkali?

Soluble base

Acid + Metal →

Salt + H₂

Acid + Metal Carbonate →

Salt + H₂O + CO₂

Acid + Metal Oxide →

Salt + H₂O

What is a solute?

Substance that dissolves to make a solution

What is a solvent?

Substance that dissolves a solute

What is a solution?

Combination of a solute and solvent

How does dissolving work?

Particles of solvent collide with solute; solute is surrounded and moved away until evenly spread through solvent

What is a saturated solution?

Solution where no more solute can dissolve in an amount of solvent

What does solubility of gases depend on?

Pressure and temperature

As pressure increases, more gas molecules will

dissolve into the solvent

Why do fizzy drinks go ‘flat’ quicker on a hot day?

Gases tend to be less soluble as temperature of solvent increases

What is a precipitate?

Insoluble product that forms when two solutions mix and react

What is an exothermic reaction?

Energy given out (exited) to surroundings:

1.      Heats up surroundings (i.e. heat ↑ energy ↓)

2.      Heats up chemicals in reaction

a.      Bond forming

Examples of exothermic reactions

• Anything burning (combustion) e.g. wood, petrol

• Respiration

• Neutralisation i.e. acid + base

> Hand warmers

What is an endothermic reaction?

• Energy enters (taken in) from surroundings

• (i.e. heat ↓ energy ↑)

Examples of endothermic reactions

• Photosynthesis

• Thermal decomposition of calcium carbonate

• Lightning

• Ice packs

Reaction profile diagram

Energy level diagram

Which reactions are exothermic?

Reactions 1, 3, 4

Which reactions are endothermic?

Reaction 2

What is temp. in terms of particles?

measure of average speed of particles (kinetic energy)