science 4thq chem reactions

• TEMPERATURE: When you raise the

  temperature of a system, the molecules bounce

  around a lot more.
• CONCENTRATION: If there is more of a

  substance in a system, there is a greater chance

  that molecules will collide and speed up the rate of

  the reaction.
• PRESSURE: Pressure affects the rate of reaction,

  especially when you look at gases. When you increase

  the pressure, the molecules have less space in which

  they can move. That greater density of molecules

  increases the number of collisions.
• CATALYST - The rate of a reaction can be increased by adding a

  suitable catalyst. A catalyst is a substance which

  increases the rate of a chemical reaction but it is not

  used up (remains chemically unchanged at the end). It

  provides an alternative reaction pathway of lower

  activation energy.
• 1. FOOD AND PHARMACEUTICAL PRODUCTS

  PRESERVATION – Temperature is a very essential

  factor is preserving foods and medicines.
• PRESERVATION AND DECOMPOSITION OF

  SPECIMEN – Biochemical laboratories make use of

  liquid nitrogen as cryogenic freezer in preserving

  laboratory specimens and samples.
• MEDICATION OR POISON EFFECTING THE

  BODY – It is essential to know the right concentration

  of the drugs that we take. Some drugs are more

  effective when taken in high concentration.
• DATING, RESTORATION, PRESERVATION OF

  ARTIFACTS – To preserve wood and leather artifacts,

  these must be soaked in polyethylene glycol, these

  chemical minimize the surface area between the

  reactants.
• POWER COMPANIES – this concept is applied in

  some power companies that burn coals.
• CONTROL OF FIRE – Usually gases have higher

  surface area and spreads out easily.
• ACTIVATION ENERGY – it is the minimum

  amount of energy to initiate a chemical reaction.
• ENDOTHERMIC REACTION – Energy is being

  absorbed.
• EXOTHERMIC REACTIONS – energy is being

  released, it releases heat causing the surrounding

  to rise the temperature.
• LAW OF CONSERVATION OF MASS

  • Also known at Lomonosov-Lavoisier Law

  • It states that the mass of the reactants must always be equal to the

  mass of the products.
• LAW OF DEFINITE PROPORTION

  • First observed by Louise Proust and confirmed by Jean Servais Stas

  after 50 years.

  • It states that the elements combined to form compound always

  contains exactly the same proportion of elements by mass.
• LAW OF MULTIPLE

  PROPORION

  • It is also known as Dalton’s

  Law, It states that if two

  elements from more than one

  compound, the ratio of the

  mass of the second element

  combining with a fixed mass of

  the first elements will be in

  ratio of whole numbers.