At the start, the gradient of the curve is the steepest. This shows that speed of reaction is the highest at the start. The concentration of the reacting particles is the highest at the start, resulting in highest speed of reaction.
As the reaction progresses, the gradient of the curve decreases. This shows that speed of reaction is slowing down. As the reactants are used up in the reaction, the concentration of reacting particles decreases, resulting in a decrease in speed of reaction.
When the gradient of the curve becomes horizontal, it shows that the reaction has stopped. Either one or all of the reactants have been completely used up, so reaction stopped.
In a storm cloud, water droplets are brought upwards in an updraft within the storm clouds. The droplets cool and freeze into hail and smaller ice particles as they rise upwards. The heavier hail particles that formed then fall back downwards, rubbing against the rising small ice particles.
Electrostatic charging by friction occurs, with the hail particles gaining electrons from the small ice particles. The heavier hail particles, which have become negatively charged, gathered at the bottom part of the storm clouds, while the lighter small ice particles, which have become positively charged, gathered at the top part of the storm clouds.
Electrons near the ground are repelled by the negatively charged bottom of the storm clouds, moving deeper into the ground, resulting in the objects on the surface of the ground becoming positively charged. As the negative charges build up at the bottom of the clouds, surrounding air particles are ionised, sending stepped leaders towards the ground. At the same time, the positively charged objects on the ground also ionise the air particles around them, sending streamers upwards towards the clouds.
When a particular stepped leader and streamer meet, a path is established, and the huge potential difference between the cloud and the object results in a massive current flow.
This huge current flow produces an enormous amount of heat, up to 30 000 deg C, which appear to us as the brilliant white-blue flash of a lightning flash.
The source of CO comes from incomplete combustion of fuels containing carbon.
Carbon monoxide combines irreversibly with haemoglobin in the red blood cells, reducing the ability of the red blood cells to carry oxygen. This can result in respiratory problems, brain damage or death.
When both substances are added at the same time, they will react to produce a salt, ammonia gas and water.
Slaked lime will be used up in the reaction, hence the acidity of the soil will not be reduced.
Fertilizers will be used up in the reaction. Ammonia gas produced will escape to the surroundings, so nitrogen element, which is needed by the plants for healthy growth, will not be absorbed by the plants.
The work done at the barrel is equal to the work done at the nozzle. Word Done = Force x Distance. The force at the barrel > the force at the nozzle, so for equal work done, distance moved by water leaving barrel per second < distance moved by water leaving the nozzle per second.
This results in a greater speed of the water leaving the nozzle.
Alternative Answer: Volume of water leaving the barrel per second = Volume of water leaving the nozzle per second.
The cylindrical volume = Base area x distance moved by the water. Since base area of barrel > base area of nozzle, so for equal volumes, distance moved by water leaving barrel per second < distance moved by water leaving nozzle per second.
This results in a greater speed of the water leaving the nozzle.
1. The hydrogen fuel cell produces water as the only waste products. No harmful gases are released to surroundings when it is used.
2. Hydrogen is an abundant resource, if a cost effective method can be used to extract hydrogen from water.
Disadvantages:
1. There is currently no cost effective method of storing the hydrogen gas.
2. There is currently no cost effective method of extracting hydrogen from seawater.
3. The process to obtain hydrogen, either from electrolysis of water, or from cracking of hydrocarbons, produces waste gases and use up large amount of energy.
When one end of the solid rod gains heat, the heat energy absorbed is converted to kinetic energy in the rod particles. The particles at this end of the rod vibrated more vigorously in their fixed positions. The increased vibration is passed on to the neighbouring particles, causing the neighbouring particles to also vibrate more vigorously. Hence the increased vibration of the particles is passed on from particle to particle, till the particles at the other end of the rod also vibrate more vigorously.
When the average kinetic energy of the particles in the rod increases, the temperature of the rod increases. Heat energy is hence transferred from the hotter end of the rod to the cooler end of the rod through vibration of particles.
In metals, besides particle vibration, there is also electron diffusion to transfer the heat energy. The delocalised electrons are able to move more freely, hence heat conduction in metals is faster compared to non-metals.
Sunlight reaches Earth’s atmosphere and is scattered in all directions by all the gases and particles in the air. The visible light rays of sunlight consists of the spectrum of red, orange, yellow, green, blue and indigo light rays. Blue light is scattered more than the other colors because it travels as shorter, smaller waves. The scattered blue light high up in the atmosphere causes the sky to appear blue.
