N5 chemistry unit1

• The average person can walk 1 mile in 18 minutes
• compounds are 2 or more elements that are chemically combined, held together by very strong bonds and cannot be easily separated back into its original elements
• mixtures occur when 2 or more elements come together without reacting, held by weak bonds so can easily be returned back into its original elements
• the procedure for hydrogen gas is placing a burnt splint into a test tube of hydrogen
• the test for hydrogen is that it burns with a pop
• the procedure for oxygen is placing a glowing splint into a test tube of oxygen
• the test for oxygen relights a glowing splint
• the procedure for carbon dioxide is slowly blowing into a test tube of lime water with a straw
• the test for carbon dioxide is that it turns lime water cloudy/milky
• Solution is the mixture formed when a solute dissolves in a solvent
• solute is the substance that dissolves
• a solvent is the substance which other substances dissolve in
• soluble is a substance which can dissolve
• insoluble is a substance which cannot dissolve
• dilute solution is a small amount of solute dissolved in solvent
• concentrated solution is a large amount of solute dissolved in solvent
• saturated solution is the maximum amount of solute dissolved in solvent
• when chemical reactions occur, a new substance is always formed
• signs of chemical reaction is:

  colour change

  temperature change

  gas given off

  solid formed
• exothermic reactions release heat energy
• in exothermic reactions, the products have less energy than the reactants
• endothermic reactions take in heat energy
• in endothermic reactions, the products have more energy than the reactants
• compounds which contain only 2 elements end in ide
• compounds which contain 2 elements and oxygen end in ite or ate
• the rate of reaction is how fast the reaction happens
• for chemical reactions to happen, particles must collide (bump into each other) this is known as the collision theory
• a reaction only occurs when the reactant molecules have enough energy to collide successfully to form products
• when particles are made smaller their surface area increases
• decreasing particle size increases surface area, therefore increasing reaction rate
• increasing particle size decreases surface area, therefore decreases reaction rate
• increasing temperature increases the rate of reaction because the particles collide more often with more energy, so there are more successful collisions, and the reaction rate increases
• catalysts are substances which speed up a reaction without being used up in the process
• enzymes are known as biological catalysts
• catalysts allow reactions to occur using less energy
• zymase is the enzyme used in the fermentation of yeast
• amylase is the enzyme found in saliva to breakdown starch
• lipase is the enzyme used to break down fats
• the progress of chemical reactions can be followed by measuring the change in:

  mass

  volume

  concentration
• average rate of reaction=

  change in quantity / change in time