S3 - Rates of Reaction

• What are the signs of a Physical change?


  ~ No new substances are formed

  ~ They are usually easy to reverse
• Example of a Physical change?


  Ice Melting
• What are the signs of a Chemical change?


  ~ New substance(s) are formed

  ~ Are usually difficult to reverse
• Example of a Chemical change?


  Rusting
• Indicators of a Chemical Reaction (other than new substances)


  ~ Colour Change

  ~ Solid Formed (Precipitate)

  ~ Change in Temperature

  ~ Light Produced

  ~ Bubbles Produced (effervescence)
• What happens during an Exothermic reaction?


  Energy is released causing an increase in temperature
• Example of an Exothermic reaction?


  Combustion - We use the heat liberated to power cars, cook or heat buildings
• What happens during an Endothermic reaction?


  Energy is absorbed causing a decrease in temperature
• Example of an Endothermic reaction?


  Ice Packs - We use the cold to treat injures
• The higher the concentration the…


  Faster the rate of the reaction is. This is due to the greater chance of molecules colliding in the reactions
• The presence of a catalysts…


  Increases the rate of the reaction. Catalysts hold reactants in place reducing the energy needed for the reaction to occur
• When the particle size is bigger the rate of the reaction is…


  Slower, Surface area gets smaller with increasing size with increasing size, meaning a smaller area for the reaction to undergo
• If the temperature gets higher the rate of reactions is…


  Increased, the molecules move faster with increasing temperature, increasing the chance of collisions between them
• What is a Physical change?


  A process in which a new substance is not formed. Examples include a change in physical state, e.g. melting
• Chemical change 


  A process in which a new substance has been formed due to a rearrangements of atoms, e.g. Combustion (carbon dioxide and water are formed). Indicators of chemical reactions are clues to a chemical reaction taking place
• In a reaction rate line graph, the steeper the line the…


  Faster the reaction
• In a Table the IV is in the…

  first column
• In a table the DV is in the…


  second column
• Where are units in a table?


  Units are only included in brackets in the headings
• Is the independent variable is in words you will make a…


  Bar graph
• Is you have two columns of numerical values you will have a…

  Line graph
• If you have a line graph a line of ____ ___ is generally used

  Best fit
• Describe what a physical change is

  Process in which a new substance is not formed. Examples include a change in physical state, e.g. melting.
• Describe what a chemical reaction is

  Process in which a new substance has been formed due to a rearrangements of atoms, e.g. combustion (carbon dioxide and water are formed).
• When an iron rusts, the metal goes from shiny grey to brown. Is rusting a chemical reaction?

  It is a chemical reaction
• A glass is shattered. Is that a chemical reaction or a physical change?

  It is a physical change
• Some hand warmers get hot when they are shaken. Is that a chemical reaction or a physical change? How do you know?

  It is a chemical reaction because heat is produced due to a chemical reaction between the contents of the hand warmer.
• Fireworks emit light and heat as they explode. Is that a chemical reaction or a physical change? Is it fast or slow?

  It is a chemical reaction. It is a fast reaction.
• What happens when a reaction takes energy from the surroundings? What do you call this reaction?

  Endothermic reaction
• What do you call a reaction that warms up the surroundings as it occurs? Give an example of one of these reactions that we may use for our advantage and what use we make of it.

  Exothermic reaction. An example is combustion - we use the heat liberated to power cars, cook or heat buildings.
• A reaction carried out with hydrochloric acid 1 M in concentration is performed again using hydrochloric acid 2 M. What is the effect on the reaction rate?

  the rate of reaction increases with increased concentration.
• A reaction carried out wih hydrochloric acid 1 M in concentration is performed again using hydrochloric acid 2 M. What is the effect on the reaction rate?

  The rate of reaction increases with increased concentration
• Name a useful catalyst in our daily lives and explain how it is important to us.

  Enzymes are natural catalysts. They control how quickly chemical reactions happen inside living things.
• Could you explain why catalysts increase the rate of reaction?

  Lower activation energy
• Zinc lumps reacts with hydrochloric acid giving off hydrogen/ Would the effervescence be more vigorous if zinc powder was used? Why?

  Yes. It would be more vigorous because zinc power has more surface area so there is more reactivity
• Food rots due to a chemical reaction. Would food rot quicker in winter or in summer? Why?

  Summer. Warmer temperatures in summer speed up chemical reactions, including the decomposition of food.
• List 4 factors which will increase the rate of a chemical reaction and explain how each one increases that rate.

  Temperature - Increases the movement of the molecules

  Concentration - There are more particles moving together

  Particle Size - Because of the larger surface area, there is a faster rate of reaction

  Catalysts - Makes the particles move faster or slower in a reaction
• How do you calculate the average rate of reaction?

  Rate = △ Quantity

  ————————-

  △ Time
• What is an exothermic reaction?

  An exothermic reaction is a chemical reaction that releases heat to its surroundings.
• What is an endothermic reaction?

  An endothermic reaction is a chemical reaction that absorbs heat from its surroundings, resulting in a decrease in temperature.