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Biology 2018 Solutions for Leaving Cert Higher Level

You can access the paper via the examinations.ie website. No marking scheme is available at the time of writing. You may also like: Leaving Cert Biology.
Q1. (a) 1. To receive energy for cellular reactions to occur 2. For growth and repair  (b) Many sugar units joined together  (c) Cellulose  (d) Contains glycerol and three fatty acids  (e) Phospholipids are found in cell membranes  (f) Biuret test 
Q2. (a) Living factor  (b) The place where an organism lives  (c) All of the different populations living in an area  (d) All members of the same species living in an area  (e) The functional role of an organism in an ecosystem  (f) The part of the Earth that sustains life  (g) Checking for the presence or absence of an organism in an ecosystem 
Q3. (a) Interphase  (b) Cell division in which one cell becomes two cells and the number of chromosomes is retained. The genetic material of the daughter cell is identical to the mother cell.  (c)1. The chromosome number is halved in meiosis  2. Meiosis involves 2 c…

Collision Theory

Collision theory

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This accounts for the factors that influence the rate of reaction.

For a reaction to occur the reacting particles must collide with each other.

A collision only results in the formation of products if a certain minimum energy is exceeded in the collision - this is then described as an effective collision.

An effective collision: occurs when bonds are broken and new bonds are formed, bringing about the formation of products.

The rate of reaction depends on the number of e effective collisions per second between reacting particles.

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Activation Energy: 

is the minimum energy that colliding particles must have for a reaction to occur. Denoted Ea.

Low activation energy means a faster rate. Conversely, high activation energy means a slower rate.

1. Temperature:
increased temperature means that the kinetic energy of the molecules increases. Therefore, more collisions occur and hence more effective collisions must occur.

2. Nature of the reactants:
covalent compounds have to break bonds to react and
therefore they need more energy and so they have a higher activation energy.

3. Particle size:
smaller particles have a larger surface area for more collisions to occur. Therefore, more e ective collisions will occur and hence they will reach the activation energy more rapidly.

4. Concentration:
greater concentration means more particles and therefore more collisions, and hence more e ective collisions. Thus, the activation energy is reached more rapidly.

5. Catalyst:
it provides an alternative pathway with a lower activation energy.

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