Physics 2 Past Paper PDF

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TolerableVirginiaBeach

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gas exchange plant biology thermodynamics physics

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This document covers various topics in physics, including gas exchange in plants, plant control systems, phototropism, gravitropism, and nastic responses. It also discusses the laws of thermodynamics, including energy conservation and efficiency, and provides examples of calculating specific heat capacity and heat of fusion/vaporization.

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## Gas exchange in plants - In leaves: CO2, O<sub>2</sub>, H<sub>2</sub>O move by diffusion from plant cells / saes to/from stomata - Day: CO<sub>2</sub> consumed, O<sub>2</sub> released (Photosynthesis) - Night: O<sub>2</sub> consumed, CO<sub>2</sub> released (Cellular respiration) - Water i...

## Gas exchange in plants - In leaves: CO2, O<sub>2</sub>, H<sub>2</sub>O move by diffusion from plant cells / saes to/from stomata - Day: CO<sub>2</sub> consumed, O<sub>2</sub> released (Photosynthesis) - Night: O<sub>2</sub> consumed, CO<sub>2</sub> released (Cellular respiration) - Water is lost by evaporation (transpiration) to minimize water loss. - Opening and closing of stomata is by turgor pressure in guard cells - Stomata opens for water, closes when loses too much water. - **Turgor Pressure** - how much water in a cell. - A lot of water is high turgor pressure; guard cells open/swell. - Not much water is low turgor pressure; guard cells close/shrink. - **Lenticels** - lens-shaped opening allow gas exchange (woody plants) ## Plant control systems - **Stimuli** - Changes in environment trigger response in an organism. - **Tropism** - Responses to stimuli; plant grows away/ toward stimulus. - **Auxin** - Actively transported through cells for plant growth - Stems: increases cell growth - Roots: decreases cell growth ## Phototropism - Allows stem to curve away/ toward light. - **Positive** growth: towards light - **Negative** growth: away from light ## Gravitropism - Growth due to gravity. - **Positive** growth: into soil; towards force of gravity - **Negative** growth: upwards; against force of gravity ## Nastic Response - Plants respond to touch ## Laws of thermodynamics 1. Energy cannot be created or destroyed, only changed from one form to another 2. No process can be 100% efficient - Always some energy is converted into heat (thermal energy) ## Global systems ### Calculating specific heat capacity - **Only used when there is temperature change** (C, Specific Heat Capacity is always given). - Q = m * c * delta T - **Q** = Energy in Joules (J) or kilojoules (kJ) - **m** = mass (g) - **c** = Specific Heat Capacity - **delta T** = Change in temperature (Celsius) - **Example**: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Q = m * c *(T<sub>final</sub> - T<sub>initial</sub>) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Q= 5.2 kJ = 5200 J &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; m = 46.94 g &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; c = 4.19 J/g * C &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; delta T = T<sub>final</sub> - T<sub>initial</sub> = 5 (C) &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5200 J = 46.94 * 4.19 * 5 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; T<sub>final</sub> = 51.7 C ### Calculating Heat of Fusion / Vaporization - **Fusion (fus)** - Amount of energy to melt a substance - Q = n * delta Hfus - **Q** = Energy in Joules (J) or kilojoules (kJ) - **n** = moles - **delta Hfus** = Heat of Fusion (kJ/mol) - **Example**: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Q = 0.429 * 13.08 kJ/mol &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Q = 5.6 kJ - **Vaporization (vap)** - Amount of energy to evaporate a substance - Q = n * delta Hvap - **Q** = Energy in Joules (J) or kilojoules (kJ) - **n** = moles - **delta Hvap** = Heat of Vaporization (kJ/mol) - **Example**: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Q = 100 kJ &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; n = Q / delta H<sub>vap</sub> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; n = 100 / 4.64 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; n = 2.46 moles &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Q = 2.46 moles * 4.64 kJ/mol &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Q = 11.45 kJ &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;