- Limestone is mainly made of calcium carbonate (CaCO3) - this means it will contain other impurities.
- It is a sedimentary rock formed from the remains of tiny animals and plants that lived millions of years ago.
- Its main use is as a building material
- Powdered limestone can be heated with clay to make cement.
- Cement mixed with water, sand and crushed rock, produces concrete in a slow chemical reaction.
- Heating limestone at a very high temperature causes a thermal decomposition reaction to occur
- calcium carbonate --> calcium oxide + carbon dioxide
- Buildings made from calcium carbonate are badly damaged by acid rain.
- calcium carbonate + acid rain --> calcium salt + water + carbon dioxide
The Limestone Reaction Cycle
1. If we start with calcium carbonate and heat it strongly we end up with calcium oxide
2. If we add a small amount of water to the calcium oxide we get calcium hydroxide.
3. If we then add more water and filter we get lime water or calcium hydroxide solution.
4. We then add carbon dioxide to lime water and we get back to our calcium carbonate.
Common mistakes that students make in this unit are:
- They not take into account the social, moral and ethical issues associated with quarrying limestone
- They forget that limestone is a carbonate and cannot apply knowledge of the reaction cycle to a different carbonate.
Try the question below:
1a. They were not directly in front of the chimney and they were only around it. The scientists could have been biased towards the company.
ReplyDeleteb. They used evidence that measured the concentration of particles and only ones that were above a certain size.
1c. Particles lower than the amount cause cancer and asthma attacks. The concentration would probably be higher nearer the chimney and it was already detected to be 1.8ppm while the sensors were quite spread out. The wind still blows the particles in the direction of the residents.
1a.The local residents were not positioned directly where the concentration of the particles will be the highest.
ReplyDeleteThey were not in the position where the downwind will affect them.
1b. The average concentration of any particle will be less than 2ppm which means that there will be no risk to health.
1c.The local residents were concerned about there was a risk to the health because children started to suffer from asthma attacks, the sensors did not detect particles below the size of 0.5mm and the results were an average showing the results to be more reliable.
1a) They were spread out from the actual chimney so you wouldn't get accurate results. They didn't put sensors around the local resident area.
ReplyDelete1b) The size of the particle and the concentration ppm
1c) The particles size, ppm could increase over time. The wind direction is towards them so they get most of the particles. The sensors only detected particles higher than 0.55ppm so they didn't measure the ones that actually cause medical risks
1a. The sensors are not in line of the limestone particles moving towards the residences.
ReplyDelete1b. the scientists used the data which provided the concentration of particles above 0.5mm
1c. There could be particles under the size of 0.5mm which can cause asthma and possibly cancer; the most concentrated particles would travel towards the residents, children would still be affected by the particles and can develop dangerous health condition at an early age.
1 a) No sensor was put in front of the town. None were put in the direction of the wind.
ReplyDeleteb) There was only 1.8 ppm which is less than the maximum and the smallest particle size was 0.5 mm which is not known to have any medical effects.
c) They did not agree with the placement of the sensors. Their children still suffered from asthma attacks. There were far too many ppm for comfort.
1a) They did not put any sensors around the area of the local residents and the sensors were not placed close by to the chimney.
ReplyDeleteb) The particle sensor showed that the average concentration of particles was 1.8 ppm and particles larger than 0.5 were only detected, which results in no risk to health.
c) Particles lower than the 0.5 could still cause asthma attacks and cancer, the particles could increase over time and the direction of wind would cause concentrated particles to travel towards the local residents.
1a) One reason for why the local residents objected the placement of the sensors was because the sensors weren't positioned directly where the concentration of the particles will be the highest. Also because none of the sensors are actually within the local area, so they are irrelevant.
ReplyDelete1b) Sciwntist concluded that there wwas no risk to health because the particle sensor showed that the average concentration of particles was 1.8 ppm. This means it is safe as only particles over 2 ppm are harmful.
1c) One reson for why the local resident were concerned is because the sensor used could only detect particles over 0.5 mm, therefore it couldn't detect any harmful particles. Also there was an increase in the local area of children suffering from asthma attacks. Finally, the wind direction shows that the particles from the cement work blows towards them.
a. The sensors are around the cement works and not near the chimney. Also, the sensors are not near the area where the local residents live, hence it may not show the concentration that affects the residents.
ReplyDeleteb. As the average concentration of particles was 1.8ppm, which is less than 2ppm, the scientists concluded the results by saying that there is no risk.
c. The sensors could only measure concentration of particles that were larger than 0.5mm, so they could not detect the smaller particles that may cause asthma attacks or cancer. In addition to this, if the concentration of particles was 1.8ppm around the cement works, then near to the chimney it would have been more than 2ppm which can damage health. Furthermore, the diagram shows that the direction of the wind is towards the local residency, which means that the dangerous particles can still reach them.
a) the local residents would object to the position of the sensors because they were far away from the local residents area so it would not detect how much particles in the local area. Also they were not placed where the direction of wind was blowing the particles
ReplyDeleteb) The four sensors only detected particles that were larger than 0.4 and this has no medical risks
c) There could have been particles smaller than 0.4mm which cause medical problems. The concentration of the particles were 1.8ppm which is close to 2ppm and this concentration is harmful.The investigation was unreliable as it was not carried out in the local area where the residents live .
This comment has been removed by the author.
ReplyDelete1a) The sensors were not within the local are so there was no difference. Also, the sensors were positioned at a place where only the lowest concentration of particles would be visible.
ReplyDeleteb) Only particles over 2ppm would be harmful but the particles in this case was 1.8ppm.
c) The local residents were still concerned because less than 0.3mm would still be the cause of cancer. Furthermore, less than 0.2mm would still be the cause of cancer. Finally, the usual direction of wind couldchange the directions that the concentrated particles travel.
Less than 0.3mm would still be the cause of asthma attacks* (instead of 0.3mm would still be the cause of cancer. Furthermore, less than 0.2mm would still be the cause of cancer.)
ReplyDelete1a) The sensors were placed around the cement works rather than the chimney and there were no sensors placed near the local area, thus the results would not be reliable.
ReplyDelete1b) The scientists concluded that the average concentration of particles was 1.8ppm and so there was no risk becuase any particles above the size of 0.5mm do not risk health.
1c) The direction of the wind is from the chimney to the local residents and so the particles would be carried there by the wind. Concentration higher than 2ppm can risk health and the average concentration of 1.8ppm may slightly increase to 2ppm. Lastly, the scientists used sensors that would not detect particles that my cause asthma or cancer and so they could be present.