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Showing posts with label PISA. Show all posts
Showing posts with label PISA. Show all posts

Sunday, February 7, 2021

pH CHANGE AS THE CAUSE OF TOOTH DECAY

 Tooth decay starts when the pH of the mouth is lower than 5.5. Tooth enamel, made up of calcium hydroxyapatite (a crystalline form of calcium phosphate) is the hardest substance in the body. It does not dissolve in water, but is corroded when the pH in the mouth is below 5.5. Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth after eating. The best way to prevent this is to clean the mouth after eating food. Using toothpastes, which are generally basic, for cleaning the teeth can neutralise the excess acid and prevent tooth decay.

You might have heard that the pH level in the body affects your health. Studies have shown that lower, or acidic, pH levels are associated with a greater risk of serious health conditions including type 2 diabetes, heart disease, and obesity. Studies have also shown that higher, or alkaline, pH levels are linked to improvements in memory and cognition, reduced pain, and lower risk of hypertension (high blood pressure), and stroke.

Another interesting link is pH levels and bone health.  Extensive research has been conducted on the effects of pH on bone health, and studies have discovered that low-acid diets can help improve bone density. According to Dr Sara Gottfried, the Journal of Nutrition published a study that stated that alkaline mineral waters can decrease bone resorption and even lower parathyroid hormone levels which regulate the release of calcium from bone.

An alkaline diet is one that incorporates foods that can increase the pH levels. Interestingly, an alkaline diet is associated with an increase in growth hormone which can burn fat, improve libido, and retain a general sense of well-being.

Maintaining a good pH balance in the mouth allows a healthy balance of good and bad bacteria. Many of the good bacteria in our mouth are harmless and some bacteria, known as probiotics, aid in the digestion of foods. Other good bacteria actually protect our teeth and gums.

Certain foods, such as sugary beverages, snacks, and some grains, increase the acidity in the mouth. The pH of the mouth can change dramatically with the types offoods we eat. Foods that are highly acidic, like lemons, lowers the pH, while foods like melons increases the pH.

The saliva can help neutralize the acid, but eating acidic foods can increase the acidity of the saliva. If the pH takes a long time to neutralize in the mouth, it may give bad bacteria enough time to wreak havoc on the teeth and gums. Typically it may take a few minutes or a few hours for the pH to neutralize. An acidic mouth is an optimal environment for bad bacteria to grow, and if given the time and the ability, it can cause tooth decay.

Question 5.1 The pH of mouth is generally-

(a) Less than 7

(b) Greater than 7

(c) Equal to 7

(d) Cannot be determined.

……………………………………………………………………………………………………………………………………………..

 

Q5.2 The hardest substance in the body has _______________ and __________ elements as the major components.

……………………………………………………………………………………………………………………………………………………

Q5.3 What according to you, could be the reason of not allowing the kids to eat plenty of chocolates?

Q 5.4 Give two benefits of having an alkaline diet.

Answer-key

5.1 (a) less than 7- Full credit.

Any other response- no credit

5.2  Calcium and Phosphorus– Full credit

Calcium, phosphorus and oxygen – Full credit

Any one of Calcium, phosphorus and oxygen – partial credit

Any other response- no credit

5.3 Sugary substances turn into acidic when reacted with saliva in our mouth. This acid decays the teeth and is the reason of cavity in the teeth. – Similar responses – full credit.

Any other response- no credit

5.4Higher, or alkaline, pH levels are linked to improvements in memory and cognition, reduced pain, and lower risk of hypertension (high blood pressure), and stroke. Low-acid diets can help improve bone density. It allows a healthy balance of good and bad bacteria in the mouth and helps prevent tooth decay. – Any two of these responses- full credit.

Any other response – no credit

Refined sugar

 Sucrose is a common sugar. It is a disaccharide, a molecule composed of two monosaccharide units ie glucose and fructose. Sucrose is produced naturally in plants, from which table sugar is refined. It has a molecular formula C12H22O11.‌Refined sugar is made by extracting and processing the sugar naturally found in foods like corn, sugar beets, and sugar cane. This refined sugar is then added to foods for various purposes, such as to boost flavor.

Refined sugar is harmful for health. Children are very fond of ice cream, cold drinks, chocolates, and sweets, etc. which contain refined sugar. Higher intake of refined sugar forms acid in mouth which reacts with calcium phosphate present in enamel and tooth decay starts. These days children have lots of cavities. Lots of people are suffering from diabetes.

Q10.1 The chemical compound present in cane sugar is

     a.      Sucrose

     b.      Glucose

     c.       Fructose

     d.      Lactose

 Q10.2 The molecular mass of sucrose is

     a.      352 u

     b.      342 u

     c.       364 u

     d.      326 u

     Q10.3 If 3.42 gm of sucrose is dissolved in 18gm of water in a beaker. Estimate the number of oxygen atoms in the beaker.

       -------------------------------------------------------------

Q10.4How much do you agree with the following statement?

 

 

 

Strongly Agree

Agree

Disagree

Strongly disagree

a

Refined sugar is the only cause of tooth decay

 


 

 

b

One should always have sugar free diet




 

Answer Marking Scheme


10.1. Full  credit :2 if response is a  as Sucrose is produced naturally in plants

          No credit :0 if response is b, c, d

10.2). Full  credit :2 if response is b as sucrose has a molecular formula C12H22O11;12 x 12+22 x 1 + 11 x 6 = 342

          No credit :0 if response is a, c, d

10.3) . Full  credit :2 if response is 6.68 x 1023 :0.01mole of sucrose contains 11 x 6.022 x 1023 = 6.6242 x 1022 oxygen

    Total oxygen in solution =(6.022+.662) x 1023 =6.684 x 1023

    Partial credit :1 for correct formula

        No credit :0 for wrongly calculated

10.4 (a) Full  credit:2 if response is strongly disagree

             Partial credit :1 if response disagree

             No credit :0 other response or missing

   (b)   Full  credit :2 if response is strongly disagree

Partial credit :1 if response disagree

                      No credit :0 other response or missing 


















MANUFACTURING PROCESS OF SOAP

 

The fats and oils required for manufacturing soap are extracted from the plants and animals.  To make the fatty acids called triglyceride molecule, 3 fatty acid molecules are bonded to 1 molecule of glycerine. Fatty acids are weak acids composed of 2 parts. A carboxylic acid group having 1  hydrogen atom, 2 oxygen atoms, and 1 carbon atom and a hydrocarbon chain attached to the carboxylic acid group. Earlier the alkali required for making soaps were obtained from the animals but now they are clinically composed. The common alkalis used in soap making are sodium hydroxide and potassium hydroxide.

 

Q4.1 . Why do we consider fatty acid as weak acid?

……………………………………………………………………………………………………………

Q4.2. How  are atoms in  “Acid” functional group  bonded together?

…………………………………………………………………………………………………………………………………………

Q4.3. Each chemical has common name such as sodium chloride known as common salt .Similarly NaOH and KOH also have common names. Give the names.

.................................................................................................................................

Q4.4. Sonali’s mother has cracked hands due to washing clothes regularly. What are the possible  reasons of it ?

…………………………………………………………………………………………………………………………………………..

Answer key-

4.1 full credit : low ionization when dissolve in water  or low conductivity of electricity

       Partial credit: any one given above

4.2 Full credit :  structure  of –COOH

        No credit : other response

4.3 Full credit : caustic soda and caustic potash

     Partial Credit :  Any one of the above

     No credit : other response

4.4 Full credit : Due to soap with high amount of NaOH(base).

      No credit : other response



Valence

Valence, also spelled valency, in chemistry, the property of an element that determines the number of other atoms with which an atom of the element can combine. Introduced in 1868, the term is used to express both the power of combination of an element in general and the numerical value of the power of combination.

The explanation and the systematization of valence was a major challenge to 19th-century chemists. In the absence of any satisfactory theory of its cause, most of the effort centred on devising empirical rules for determining the valences of the elements. Characteristic valences for the elements were measured in terms of the number of atoms of hydrogen with which an atom of the element can combine or that it can replace in a compound. It became evident, however, that the valences of many elements vary in different compounds. The first great step in the development of a satisfactory explanation of valence and chemical combination was made by the American chemist G.N. Lewis (1916) with the identification of the chemical bond of organic compounds with a pair of electrons held jointly by two atoms and serving to hold them together. In the same year, the nature of the chemical bond between electrically charged atoms (ions) was discussed by German physicist W. Kossel. After the development of the detailed electronic theory of the periodic system of the elements, the theory of valence was reformulated in terms of electronic structures and interatomic forces. This situation led to the introduction of several new concepts—ionic valence, covalence, oxidation numbercoordination number, metallic valence—corresponding to different modes of interaction of atoms.

Q1. Why do Helium, Neon and Argon have zero valency?

 -----------------------------------------------------------------------

Q2. Helium has 2 electrons in its valence shell but its valency is not 2. Do you agree?

 -----------------------------------------------------------------------------

Q3. Ramesh answered that 35Cl and 37Cl have different valences. Do agree with his answer, justify.

 ---------------------------------------------------------------

Q4. An atom with 3 Protons and 4 Neutrons will have a valency ………………

ANSWER KEY-

(1)Full credit: Helium has 2 electrons in its only energy shell, while Argon and Neon have 8 electrons in their valence shells. As these have maximum number of electrons in their valence shells, they do not have any tendency to combine with other elements. Hence they have a tendency equal to zero.

No credit: Other responses and missing.

(2). Full credit:No.  Its duplet is complete. Hence the valency is zero.

No credit: Other responses and missing.
(3) Full credit:No.35Cl and 37Cl will have same valency. Valency is determined by number of protons or number of electrons. Since the number of protons/electrons are same in both the cases mentioned above, the valencies will be same.
No credit: Other responses and missing.
(4) Full credit:   ANS-1.

No credit: Other responses and missing

Full credit:        ANS-1.

No credit: Other responses and missing

Horrendous air pollution in India

India is once again heading into the worst time of year for air pollution, a season where the country’s notoriously poor quality becomes even more toxic. The main cause of deteriorating quality of air is- petrol and diesel-based vehicle exhaust fumes, coal and petroleum power plants, exhaust from industrial plants and factories and other human activities. Burning of fossil fuels releases carbon dioxide, methane, nitrogen and particulates into the atmosphere. A whopping nine in 10 people on Earth breathe highly polluted air, and more than 80 percent of urban dwellers have to endure outdoor pollution that exceeds health standards, according to the WHO’s World Global Ambient Air Quality Database. Cities like Kanpur, Faridabad, Delhi, Varanasi and Patna are polluted badly by vehicles and have large number of coal and petroleum-based industries.

Drawing on measurements and calculations as of 2016 from air monitoring stations in 4,300 cities, the WHO reported in March that India’s cities suffer the most.

Cities with the highest small particulate measurements in the world

Country

  City

  PM2.5 (µg/m³)

IndiaIndia

KanpurKanpur

173173

IndiaIndia

FaridabadFaridabad

172172

IndiaIndia

VaranasiVaranasi

151151

IndiaIndia

GayaGaya

149149

IndiaIndia

PatnaPatna

144144

IndiaIndia

DelhiDelhi

143143

IndiaIndia

LucknowLucknow

138138

CameroonCameroon

BamendaBamenda

132132

IndiaIndia

AgraAgra

131131

IndiaIndia

MuzaffarpurMuzaffarpur

120120

IndiaIndia

SrinagarSrinagar

113113

IndiaIndia

GurgaonGurgaon

113113

World Health Organization

   Technically, the WHO doesn’t treat its data as a ranking but rather a measurement of where risks are higher. But it’s clear from the report that India is one of the riskiest countries in the world to breathe, up there with Bangladesh and Georgia. When it comes to comparing PM10 measurements of the world’s largest cities, India’s capital Delhi comes in with an annual average of 292, ahead of Cairo (284), Dhaka (147), Mumbai (104), and Beijing (92), the Washington Post noted.

Q.(1)List any four reasons for poor air quality index in so many cities in India?

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(2) What do you mean by PM as mentioned above in PM 2.5 and PM 10-

A.      Pollution Meter

B.      Particulate Matter

C.      Performance Monitor

D.     Particular Material

(3) The lungs of a person living in Shimla and that living in Delhi were compared by Dr.VivekGoyal. He noticed that the lungs of person living in Shimla were pinkish red but that of person living in Delhi for last ten years was black. Explain the cause of such difference in your own words?

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(4) From the data given above, write names of any two cities that have PM 2.5 more than 170?

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(5)Carbon-di-oxide is very important gas for maintaining the temperature of the earth. It is also needed by plants for photosynthesis. Even though it is now being considered as a pollutant. Comment

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Answer- key

(1) Full credit: Increased use of vehicles

Burning farm waste.

Industrial pollution and smoke.

Too much construction.

Partial Credit: Any three correct responses

No Credit: Any other response or no response

(2) Full Credit: Particulate matter

 No Credit: Other response or missing response

(3) Full Credit: Delhi is a polluted city, so the person’s lungs are being badly affected by the pollutants and on the other hand Shimla is a hill station with clean fresh air. So, the lungs of the person living in Shimla are pinkish red.

No Credit: No response or other response

(4) Full Credit: Kanpur and Faridabad

No Credit: No response or other response

(5) Full Credit:The level of Carbon di oxide in the atmosphere is increasing day by day by

different human activities. It traps sun rays when reflected from earth. But more CO 2 is causing global warming and changing earth’s climate.

No Credit: No response or other response

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