Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 15 Materials We Use Notes, Textbook Exercise Important Questions and Answers.
Class 7 Science Chapter 15 Materials We Use Textbook Questions and Answers
1. Fill appropriate terms in the blanks:
(white cement, soap, detergent, wearing of bones, tooth decay, hard, soft, portiand, fatty acid)
Question a.
The substance that helps water to remove dirt from the surface of material is called …………… .
Answer:
soap
Question b.
Fluoride is used in toothpaste to prevent …………… .
Answer:
tooth decay
Question c.
Soap is a salt of …………… and sodium hydroxide.
Answer:
fatty acid
Question d.
Synthetic detergents can be used in …………… water as well.
Answer:
hard
Question e.
For construction purposes …………… Cement is the most commonly used cement.
Answer:
white cement
2. Write answers to the following questions.
Question a.
How does the use of a detergent help to clean soiled clothes?
Answer:
Question b.
How will you check with the help of soap powder whether water is hard?
Answer:
Question c.
What are the important ingredients of a tooth paste and what is the function of each?
Answer:
Question d.
What are the ingredients of cement?
Answer:
Question e.
What will happen if cement is not used in making concrete?
Answer:
Question f.
Make a list of detergents, that you use. Answer: There are two types of detergents that we use, (a) Natural (b) Man-made detergents.
Question g.
What should be expected from a detergent for delicate garments?
Answer:
Question h.
What is meant by surface activity? Name three chemicals responsible for the surface activity of various detergents.
Answer:
3. What are the similarities and differences between:
Question a.
Natural detergents and Man-made detergents
Answer:
| Natural detergents | Man-made detergents |
| 1. Soap nut (ritha) and soap pod (shikekai) are the natural detergents. | 1. Soap is man-made detergent soft soap and hard soap. |
| 2. Natural detergents do not have harmful effect on human skin or on silk or woollen clothes. | 2. Soap has effect on skin and cloth because it has chemicals in it. |
| 3. Soap nut, soap pod contain a chemical saponin. | 3. Soap has acid in it, soap is sodium and potassium salt of fatty acids. |
| 4. It is naturally available. | 4. It is man made using chemicals and oil. |
Question b.
Soap and Synthetic detergents
Answer:
| Soap | Synthetic detergents |
| 1. Soap is man-made detergent, it is in use since ancient times. | 1. Synthetic detergent have taken the place of soap. |
| 2. Soap loses its cleansing property in hard water it does not give lather. | 2. Synthetic detergent can be used in hard water also. |
| 3. Soap was prepared by using animal fat and wood ash. | 3. Synthetic detergent are obtained by subjecting fats, kerosene to various chemical processes. |
| 4. Variety of soaps are available, soft soap for bathing, hard soap for washing, cleaning. | 4. Variety of synthetic detergents are available – Ariel, Surf Excel, etc. |
Question c.
Bath soap and Soap for washing clothes
Answer:
| Bath soap | Soap for washing clothes |
| 1. Soft soap is used for bathing. | 1. Hard soap is used for washing clothes. |
| 2. Soft soap is potassium salt is fatty acids. | 2. Hard soap is sodium salt of fatty acid. |
| 3. Soft soap dissolves more easily readily in water. | 3. Hard soap do not dissolve easily in water. |
| 4. Now a days many perfumes, moisturizes are mixed to make it more attractive and useful. | 4. In this type of soap now a days germicides, anti foaming agents are mixed to make it more useful. |
Question d.
Modern cement and Ancient cement
Answer:
| Modem cement | Ancient cement |
| 1. Cement manufactured from 60% lime, silica 25% and alumina 5%. the rest is iron oxide and gypsum. | 1. Romans used to make aqueous cement by mixing volcanic ash in moistened lime. It was very durable. |
| 2. It is the most commonly used cement for Construction work. | 2. It is Roman cement volcanic ash prevent cracks from spreading. |
| 3. It is called Portland Cement. | 3. It is called Aqueous Cement. |
4. Explain why –
Question a.
Soap cannot be used in hard water.
Answer:
Question b.
Oil does not mix in water. However, oil and water become homogenous if a sufficient quantity of detergent is added.
Answer:
Question c.
Synthetic detergents are superior to soap.
Answer:
Question d.
Often coloured spots are formed on clothes during washing.
Answer:
Question e.
Tobacco masheri should not be used for cleaning teeth.
Answer:
Project:
Question 1.
Visit a cement factory. See how cement is prepared and discuss the process.
Question 2.
Write a conversation based on cement houses, mud-houses and wattle-and-daub houses.
Class 7 Science Chapter 15 Materials We Use Important Questions and Answers
Fill in the blanks:
Question 1.
The principal ingredients of a toothpaste are ………………. and ………………. which remove the dirt on the teeth.
Answer:
Calcium carbonate, calcium hydrogen phosphate
Question 2.
………………. in the toothpaste helps prevent tooth decay.
Answer:
Fluoride
Question 3.
The property of a substance of spreading on a surface is called ………………. .
Answer:
surface activity
Question 4.
………………. and ………………. are the natural detergent in common use.
Answer:
Soap nut, Soap pod
Question 5.
Soap nut and soap pod contain a chemical named ………………. .
Answer:
Saponin
Question 6.
………………. is a man-made detergent.
Answer:
Soap
Question 7.
………………. is used for washing clothes.
Answer:
Hard soap
Question 8.
………………. is used for bathing.
Answer:
Soft soap
Question 9.
Hard soap is ………………. salt of fatty acids.
Answer:
Sodium
Question 10.
Soft soap is ………………. salt of fatty acids.
Answer:
Potassium
Name the following:
Question 1.
A substance which is spread on a given surface and used for cleaning.
Answer:
Surfactant
Question 2.
A chemical contained in soap nut and pod.
Answer:
Saponin
Question 3.
An element which helps prevent tooth decay which is used in toothpastes.
Answer:
Fluoride
Question 4.
The latin word which means detergent.
Answer:
Detergere
Question 5.
A cement used for construction purpose.
Answer:
Portland cement
Question 6.
A mixture of cement, water, sand and gravel.
Answer:
Concrete
Question 7.
A natural detergent.
Answer:
Soap nut
Choose the correct option:
Question 1.
Which one of these material grows on an animal
(cotton, rubber, wood, wool)
Answer:
Wool
Question 2.
Which of these is man-made?
(oranges, apples, plastic bags, tomatoes)
Answer:
Plastic bags
Question 3.
The statue is made from marble, marble is a ………….. material.
(weak, elastic, man-made, natural)
Answer:
Natural
Question 4.
Toy Duck is made from plastic. Plastic is a ………….. material.
(natural, man-made, raw, precious)
Answer:
Man-made
Question 5.
Which of these materials is natural?
(Nylon, Rock, Plastic, Polythene)
Answer:
Rock
Question 6.
Which one of these is a natural material?
(Lemonade, Cola, Water, Ice cream)
Answer:
Water
Question 7.
The toy plane made from wood. Wood is a ………….. material.
(man-made, natural, weak)
Answer:
Natural
Question 8.
Which one of these materials is natural?
(Nylon, cotton, polythene, polyesters)
Answer:
Cotton
Match the following:
Question 1.
| Column ’A’ | Column ’B’ |
| 1. Fluoride | a. Man-made detergent |
| 2. Soap nut | b. Sodium salt of fatty acid |
| 3. Soap | c. Man-made material |
| 4. Cotton | d. Prevents tooth decay |
| 5. Nylon | e. Potassium salt of fatty acid. |
| 6. Hard soap | f. Natural detergent |
| 7. Calcium carbonate | g. Natural material |
| 8. Soft soap | h. Main ingredients of toothpaste |
Answer:
| Column ’A’ | Column ’B’ |
| 1. Fluoride | d. Prevents tooth decay |
| 2. Soap nut | f. Natural detergent |
| 3. Soap | a. Man-made detergent |
| 4. Cotton | g. Natural material |
| 5. Nylon | c. Man-made material |
| 6. Hard soap | b. Sodium salt of fatty acid |
| 7. Calcium carbonate | h. Main ingredients of toothpaste |
| 8. Soft soap | e. Potassium salt of fatty acid. |
Find out:
Answer the following questions:
Question 1.
What is the source of the fluoride in a tooth paste or tooth powder?
Answer:
A naturally occurring mineral found in tooth paste and drinking water. Sodium Fluoride (NaF) is the source of fluoride in toothpaste.
Question 2.
Note down all the information given on a tooth powder/toothpaste container or carton and discuss.
Answer:
1. The carton shows the name of the company and name of toothpaste and its contains all the ingredients present in toothpaste.
2. Licence No. of company, Regd. Trade Mark of Colgate Palmolive Co-manufactured by Colgate-Palmolive (India) Ltd. Licenced user of Trade Mark made in India. Tooth paste contains 1000 ppm max of available fluoride when packed.
3. Ingredients: Calcium carbonate, sorbitol, sodium lauryl sulphate, silica, sodium silicate flavour, sodium monoflouro phosphate, sodium bicarbonate, benzyl alcohol.
4. Direction for use: Brush thoroughly atleast twice a day.
5. Children under 6 years of age should have adult supervision and use only appropriate amount.
Question 3.
Now a days why are the roads made of concrete?
Answer:
Question 4.
What causes the hardness of water?
Answer:
Can you tell?
Answer the following questions:
Question 1.
Which substances were used earlier for cleaning teeth?
Answer:
In olden times neem twigs, coal powder ash, tooth powder, salt, pomegranate rind, were used for cleaning teeth.
Question 2.
What do we use today to clean our teeth?
Answer:
Now a days we use variety of toothpastes and tooth powders to clean our teeth.
Question 3.
What do we use for cleansing our body?
Answer:
Soap, many liquid body wash are also used to clean our body.
Question 4.
What are the materials used for construction?
Answer:
Metals, wood, stone, cement, concrete, timber, bricks, metal sheet, soil, Earth, marble, aluminium, iron, steel, bamboo, glass, plastic.
Concrete: is a wet mixture of sand, gravel, cement, and water used to create building foundations, footpaths or roads.
Question 5.
Which of the houses seen in the pictures here have a strong structure? Why?
Answer:
The houses made from stone, bricks, and cement and concrete have a strong structure.
Write short notes on or Explain:
Question 1.
Natural detergent
Answer:
Question 2.
Man-made detergents
Answer:
Question 3.
Soap
Answer:
Two types of soap are:
1. Hard soap is used for washing clothes. It is a sodium salt of fatty acids.
2. (a) Softsoap is used for bathing. It is a potassium salt of fatty acids, (b) It does not cause irritation of the skin, (c) But we can’t use soap in hard water because soap does not give lather but forms a scum, (d) So, soap loses its cleansing property so now synthetic detergents have taken place of soap, (e) Synthetic detergents are obtained by subjecting these raw materials (fats and kerosene) to a variety of chemical processes, (f) These can be used in hard water as well.
Question 4.
Concrete
Answer:
Question 5.
Surface activity
Answer:
Question 6.
Explain the method of preparation of soap.
Answer:
Material required for preparation soap are 15 g sodium hydroxide, 60 ml coconut oil, 15 g salt, perfume, a glass rod, beaker, tripod, wire gauze, burner, water mould etc.
Procedure: