science yr 10 sem 2 exam revision

purpose of meiosis

gamete production

difference between mitosis and meiosis

mitosis produces diploid cells, meiosis produces haploid cells

define alleles in the context of genes, and explain how dominant and recessive alleles for a specific trait can influence an individuals genotype and phenotype

alleles are a different version of a gene that can give you different traits. A dominant allele will always show up in the trait and only one copy is needed. Recessive alleles are masked by dominant alleles and require two copies to show up in traits. Genotypes are the combination of alleles and phenotypes is how the trait appears

Explain the relationship between DNA, chromosomes and genes

DNA is the molecule that contains hereditary information. DNA is organised into tightly coiled chromosomes. Genes are a small section of DNA that code for one specific protein

Compare and contrast somatic cells and gametes in terms of their genetic content and function in an organisms life cycle

Somatic cells make up most of our body cells, and are diploid, containing 2 sets of chromosomes. Gametes are specialised cells for reproduction, and are haploid, containing only 1 set of chromosomes

explain how meiosis creates genetic variation through crossing over

During meiosis, chromosomes line up in pairs and swap sections of their genetic material. This results in the creation of new combinations of genes

explain how meiosis creates genetic variation through independent assortment

During meiosis, chromosomes line up in pairs and do so at random, when they separate, different combinations of chromosomes occur in the daughter cells

explain how meiosis creates genetic variation through fertilisation

when gametes fuse together during fertilisation, it is completely random which sperm fertilises the egg

What is the key difference between diploid and haploid number of chromosomes

diploid cells have a complete set of chromosomes, while haploid cells have only one set

what is a carrier

a person who has one copy of an allele but does not display the trait

kinetic energy definition

energy due to the motion of an object

kinetic energy forms

mechanical, heat (thermal), light, sound, electrical

potential energy definition

energy that is stored

potential energy forms

elastic, gravitational, nuclear, chemical

definition of work

using a force to move an object

Compare and contrast the differences between heat and temperature including what it measures and the factors that determine it

Heat is the thermal energy of a substance, and its determined by the type and mass of the substance. Temperature is a measure of the average kinetic energy of particles and depends on how much the particles are moving.

what happens to particles at absolute zero

particles stop moving and have no energy

what happens to pressure of gas at absolute zero

there is zero pressure - particles aren’t moving so they don’t collide with the walls of a container

Explain the relationship between pressure and temperature

As temperature increases, pressure increases. When particles have more energy they collide with the walls of the container with more energy (and force) therefore increasing pressure.

describe how energy is conserved in the water cycle

Energy is absorbed during the change of phase and is released during the opposite. E.g. absorbed energy during evaporation is released during condensation

describe how energy is lost in the water cycle

some energy radiates back into space. Overall the amount of energy absorbed from the sun is equal to the amount of energy released back into space. energy in = energy out

define barometric pressure

atmospheric pressure

example of law of conservation of energy on the water cycle

when water vapour condenses into water droplets, energy is transferred to the nearby air particles

explain how energy is transferred in evaporation

water molecules gain kinetic energy as they increase in temperature, eventually having enough energy to break free of the attractive forces holding them as a liquid. The water molecule gains potential energy as it rises

explain how energy is transferred in condensation

the water molecule cools down, transferring energy to other molecules in the atmosphere. This energy is radiated back into space

explain how energy is transferred in precipitation

water droplets gain potential energy as they get larger. The potential energy is transformed into kinetic energy as the droplet falls down to the ground.

create a flow diagram representing the flow of energy in a model of the water cycle

sun: thermal energy → water molecule: kinetic energy → water molecule above the ground: potential energy → water droplet falling down as rain: kinetic energy

explain how energy is conserved during the phase changes of water, such as when ice melts or water vapour condenses. Include the role of temperature changes

to make ice melt the temperature is increased. As ice melts, energy is absorbed from the increase in surrounding temperature by the ice in order for the particles to gain energy and break free of the attractive forces holding it together. This energy is released back into the surroundings as the particles cool back down and form a solid (freezing).

Geo engineering definition

the deliberate large-scale manipulation of an environment process that affects the earth’s climate, in attempt to counteract the effects of global warming

geo engineering benefits

can reduce or reverse the effects of human induced climate change

geo engineering risks

it may unintentionally accelerate global warming; may cause uncontrollable global cooling; may have other unknown uncontrollable side effects

law of conservation of mass

mass cannot be created nor destroyed in a chemical reaction

what does the law of conservation of mass mean when balancing a chemical equation

the total number of each type of atom present in the reactants must equal the total number of each type of atom present in the products of a chemical equation - otherwise atoms are being created or destroyed, and so the equation is not balanced

rate of reaction definition

the speed at which a chemical reaction proceeds

5 factors that can increase the rate of reaction

pressure, surface area, concentration, temperature, use of catalyst

define the collision theory

the assumption that for a chemical reaction to occur, the reactant particles must collide, in the correct orientation and with enough energy for the reaction to occur

Photosynthesis equation

6CO2 + 6H2O → C6H12O6 + 6O2

respiration equation

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP (energy)

combustion equation

CH4 + 2O2 → CO2 + 2H2O

name the primary chemical reaction responsible for the greenhouse effect and briefly describe its role in climate change

Combustion - the combustion of fossil fuels is one of the primary chemical reactions responsible for climate change as it results in the release of carbon dioxide into the atmosphere. Carbon dioxide captures heat radiated from the surface of earth and so increases the average temperature of the atmosphere

What is one example of geo engineering

Solar geo engineering, or specifically albedo enhancement involves increasing the reflectivity of clouds or the surface of earth, to reduce the amount of sunlight absorbed and re-emitted from the surface of earth

define carbon capture and storage (CCS) as a geo engineering strategy and discuss its potential role in reducing atmospheric carbon dioxide levels

Carbon capture and storage involves removing carbon dioxide from the atmosphere and storing it in carbon sinks (such as biological: trees, or geological: stored in empty former natural gas deposits). These processes have the potential to return atmospheric carbon dioxide levels back to less damaging levels

how does the activation energy relate to the collision theory, and why is it a crucial factor in determining reaction rates?

For a chemical reaction to occur the reactant particles have to have enough energy to break their bonds and then form new ones (products). This is known as activation energy. The more energy reactants particles have, the more likely they are to overcome the activation energy barrier when they collide, and so react. If the activation energy barrier is high, a reaction is likely to occur slowly, and if it is low, it is likely to occur quicly. Changing conditions (like increasing temperature) can increase the rate of reaction by increasing the energy of the particles, and so making them more likely to collide with enough energy to overcome the activation energy barrier (it doesn’t reduce the barrier)

how does the addition of a catalyst influence the collision theory and the rate of a chemical reaction

catalysts provide an alternative reaction pathway with a lower activation energy. This means that a greater proportion of collisions between reactant particles involve particles with sufficient energy to overcome the lower activation energy barrier, which means more successful collisions occur per unit time, which increases the raction rate

provide an example of a real-world application where manipulating the rate of reaction is crucial, and explain the significance of controlling the reaction rate in that context.

Cooking a sausage is an example where the manipulation of the rate of reaction is crucial. If the reaction happens too quickly, the outside of the sausage gets burnt before the inside of the sausage gets cooked. Maintaining a moderate temperature ensures that the inside of the sausage is given time to cook before the outside of the sausage gets burnt