Ch 6 : Physical and Chemical Changes

                                                      Physical and Chemical Changes

 

1. Classify the changes involved in the following processes as physical or chemical changes:

(a) Photosynthesis

(b) Dissolving sugar in water

(c) Burning of coal

(d) Melting of wax

(e) Beating aluminium to make aluminium foil

(f ) Digestion of food

Answer:

(a) Chemical change.

(b) Physical change.

(c) Chemical change

(d) Physical change

(e) Physical change

(f) Chemical change

2. State whether the following statements are true or false. In case a statement is false, write the corrected statement in your notebook.

(a) Cutting a log of wood into pieces is a chemical change. (True/False)

(b) Formation of manure from leaves is a physical change. (True/False)

(c) Iron pipes coated with zinc do not get rusted easily. (True/False)

(d) Iron and rust are the same substances. (True/False)

(e) Condensation of steam is not a chemical change. (True/False)

Answer:

(a) False (b) False (c) True (d) False (e) True

3. Fill in the blanks in the following statements:

(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of _________.

Answer: Calcium carbonate.

(b) The chemical name of baking soda is _________.

Answer: Sodium hydrogen carbonate.

(c) Two methods by which rusting of iron can be prevented are _________ and _________.

Answer: Polishing, Glavanisation.

(d) Changes in which only _________ properties of a substance change are called physical changes.

Answer: Physical

(e) Changes in which new substances are formed are called _________ changes.

Answer: Chemical

4. When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.

Answer: When baking soda is mixed with lemon juice, bubbles formed because of evolution of carbon dioxide gas. This is a chemical change, because in this reaction new substances are formed.

5. When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.

Answer: In burning of candle some of the wax melts, which is physical change, while most of the wax burnt, which is a chemical change.

In the burning of wood, water present in wood changes into vapour, this is physical change, while burning of wood is a chemical change.

6. How would you show that setting of curd is a chemical change?

Answer: In the setting of curd, milk changes into new substance, curd. This is an irreversible process that means milk cannot get back from curd. Formation of new substance and irreversible process shows that setting of curd is a chemical change.

7. Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.

Answer: In burning of wood, new substances are formed and hence is a chemical change. While cutting the wood into small pieces no new substance is formed, thus it is a physical change.

Hence, burning of wood and cutting it into small pieces are considered as two different types of changes.

8. Describe how crystals of copper sulphate are prepared.

Answer:

Process:

• Water is taken in a beaker.
• Few drops of sulphuric acid is added to the water.
• Water is let to boil.
• When water starts boiling, copper sulphate powder is added to the water with continuous stirring the solution.
• When copper sulphate starts deposited into bottom of the beaker, then solution is filtered and left for cooling.
• After cooling, the crystals of copper sulphate is prepared.

9. Explain how painting of an iron gate prevents it from rusting.

Answer: Iron get rusted because of reaction with oxygen present in moist air. By painting iron gate, iron is prevented to come into contact with oxygen present in moist air, which prevent it be getting rusted.

10. Explain why rusting of iron objects is faster in coastal areas than in deserts.

Answer: Iron get rusted because of reaction with oxygen present in moist air. In coastal areas, air contains more moisture because of sea or ocean, while in deserts air is dry and hot. Thus because of getting more moist air iron objects getting rusted faster in coastal areas than in deserts.

11. The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder it exist as a liquid. When it comes out from the cylinder it becomes a gas (Change – A) then it burns (Change – B). The following statements pertain to these changes. Choose the correct one.

(i) Process – A is a chemical change.

(ii) Process – B is a chemical change.

(iii) Both processes A and B are chemical changes.

(iv) None of these processes is a chemical change.

Answer: (ii) Process – B is a chemical change.

12. Anaerobic bacteria digest animal waste and produce biogas (Change – A). The biogas is then burnt as fuel (Change – B). The following statements pertain to these changes. Choose the correct one.

(i) Process – A is a chemical change.

(ii) Process – B is a chemical change.

(iii) Both processes A and B are chemical changes.

(iv) None of these processes is a chemical change.

Answer: (iii) Both processes A and B are chemical changes.

 

Ch 5 : Acid Base And Salt

                                                                      Acid Base And Salt

Question: 1. State differences between acids and bases.

Answer:

Question: 2. Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?

Answer:Since window cleaner turns red litmus paper to blue, it is basic in nature.

Question:3. Name the source from which litmus solution is obtained. What is the use of this solution?

Answer:

Litmus solution is obtained from lichens. Litmus solution is used to detect the acidic and basic characteristic of a substance.

Question: 4. Is the distilled water acidic/basic/neutral? How would you verify it?

Answer:Distilled water is neutral in character, i.e. it is neither acidic nor basic.

Neutral nature of distilled water can be verified by the use of blue and red litmus paper.

Distilled water does not change the colour of either blue or red litmus paper.

Question: 5. Describe the process of neutralization with the help of an example.

Answer:When the solution of acid is mixed with the solution of base in proper ratio, both of them neutralize the effect of each other and a new substance; called salt; is formed; along with water. This is called neutralization or neutralization reaction.

Example: When the solution of sodium hydroxide (a base) is mixed with the solution of hydrochloric acid (an acid) in proper ratio, both neutralize each other and the reaction mixture so obtained is neutral in character. In this reaction, a new substance sodium chloride (common salt) is formed.

The reaction involved in this can be written as follows:

Question: 6. Mark ‘T’ if the statement is true and ‘F’ if it is false:
(i) Nitric acid turns red litmus blue. (T/F)

Answer:F

(ii) Sodium hydroxide turns blue litmus red. (T/F)

Answer:F

(iii) Sodium hydroxide and hydrochloric acid neutralize each other and form salt and water. (T/F)

Answer:T

(iv) Indicator is a substance which shows different colours in acidic and basic solutions. (T/F)

Answer:F

(v) Tooth decay is caused by the presence of a base. (T/F)

Answer:F

Question: 7. Dorji has a few bottles of soft drink in his restaurant. But, unfortunately, these are not labeled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink. How will Dorji decide which drink is to be served to whom?

Answer:

Dorji would dip blue and red litmus paper in the sample of each of the bottles.

Sample of solution of bottle which turns blue litmus paper red is acidic.

Sample of solution of bottle which turns red litmus paper blue is basic.

Sample of solution of bottle which does not change the colour of either blue or red litmus paper is neutral in nature.

After detecting the acidic, basic and neutral nature of soft drink, Dorji would serve the drink to the customers according to their requirement.

Question: 8. Explain why:
(a) An antacid tablet is taken when you suffer from acidity.

Answer:

Antacid means substance that works against acid. Antacid tablet is taken in the case of acidity to neutralize the excess acid produced in the stomach.

Antacid tablets neutralize the acid produced in the stomach and give relief from acidity.

(b) Calamine solution is applied on the skin when an ant bites.

Answer:Calamine solution, which is zinc carbonate, is a base. In the case of ant bites, ant injects an acid; called formic acid; in the skin which causes pain and irritation. By applying calamine solution, it neutralizes the effect of acid inject in the course of ant bite and gives relief from pain.

(c) Factory waste is neutralized before disposing it into the water bodies.

Answer:

Most of the factory wastes contain acid. It they are flushed into water as they are, then acid present in them would kill the aquatic organisms; along with creating pollution. Thus, it is necessary to neutralize the factory waste before disposing it into the water bodies.

Question: 9. Three liquids are given to you. One is hydrochloric acid, another is sodium hydroxide and third is a sugar solution. How will you identify them? You have only turmeric indicator.

Answer:

Label the test tubes as A, B and C.

Dip the turmeric indicator in test tube A. If the turmeric paper changes to red then the liquid in the test tube is sodium hydroxide; which is a base. Otherwise, it is either hydrochloric acid or sugar solution; which is neutral.

If the liquid in the test tube A is not sodium hydroxide then keep it aside and repeat above procedure with the test tube B. If it is not sodium hydroxide then the liquid in test tube C must be sodium hydroxide.

Take aside the test tube with sodium hydroxide and pour sodium hydroxide in remaining two test tubes. The test tube which becomes warm contains acid. When acid and base neutralize each other, heat is released in the process.

Question: 10. Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.

Answer:If blue litmus paper is dipped in a solution and it would remain blue then the solution may be basic or neutral in character.

Blue litmus paper does not change its colour with basic solution and neutral solution.

Question: 11. Consider the following statements:
(a) Both acids and bases change colour of all indicators.
(b) If an indicator gives a colour change with an acid, it does not give a change with a base.
(c) If an indicator changes colour with a base, it does not change colour with an acid.
(d) Change of colour in an acid and a base depends on the type of the indicator.
Which of these statements are correct?
(i) All four (ii) a and d (iii) b and c (iv) only d

Answer:(iv) only d

Ch 4 : Heat

                                                                      Heat

Question: 1 - State similarities and differences between the laboratory thermometer and the clinical thermometer.

Answer:

Question: 2 - Give two examples each of conductors and insulators of heat.

Answer:

Examples of conductor: Iron, copper
Examples of insulator: Rubber, plastic
Question: 3 - Fill in the blanks:
(a) The hotness of an object is determined by its __________.

Answer: Temperature.

(b) Temperature of boiling water cannot be measured by a _____________ thermometer.

Answer: Clinical Thermometer

(c) Temperature is measured in degree ______________.

Answer: Celsius

(d) No medium is required for transfer of heat by the process of __________.

Answer: Radiation

(e) A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of ______________.

Answer: Conduction.

(f ) Clothes of ______________ colours absorb heat better than clothes of light colours.

Answer: Dark

Question: 4 - Match the following :
Question: 5 - Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing?

Answer: By wearing more layers of clothing, air gets trapped between different layers. This makes different layers of insulation and thus provides better protection against cold. On the other hand, wearing just one piece of clothing creates just one insulator layer and hence is less effective in beating the cold.

Question: 6 - Look at Fig. 4.13 (in NCERT Text Book). Mark where the heat is being transferred by conduction, by convection and by radiation.

Answer: 

Question: 7 - In places of hot climate it is advised that the outer walls of houses be painted white. Explain.

Answer: White colour reflects most of the heat falling on it. This makes the house colder. Thus, in places of hot climate it is advised that the outer walls of house be painted white.

Question: 8 - One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be
(a) 80°C
(b) more than 50°C but less than 80°C
(c) 20°C
(d) between 30°C and 50°C

Answer: (d) between 30°C and 50°C

Question: 9 - An iron ball at 40°C is dropped in a mug containing water at 40°C. The heat will
(a) flow from iron ball to water.
(b) not flow from iron ball to water or from water to iron ball.
(c) flow from water to iron ball.
(d) increase the temperature of both.

Answer: (b) not flow from iron ball to water or from water to iron ball.

Question: 10 - A wooden spoon is dipped in a cup of ice cream. Its other end
(a) becomes cold by the process of conduction.
(b) becomes cold by the process of convection.
(c) becomes cold by the process of radiation.
(d) does not become cold.

Answer: (d) does not become cold.

Question : 11 - Stainless steel pans are usually provided with copper bottoms. The reason for this could be that
(a) copper bottom makes the pan more durable.
(b) such pans appear colourful.
(c) copper is a better conductor of heat than the stainless steel.
(d) copper is easier to clean than the stainless steel.

Answer: (c) Copper is a better conductor of heat than the stainless steel.

ch 3 : Fibre to Fabric

                                                              Fibre to Fabric

 

Question: 1 - You must be familiar with the following nursery rhymes

a. ‘Baa baa black sheep have you any wool’.

b. ‘Mary had a little lamb. whose fleece was white as snow’.

Answer the following question.

(a) Which parts of the black sheep have wool?

Answer - The skin of black sheep have wool.

(b) What is meant by the fleece of the lamb?

Answer: Fleece means hair of the lamb.

Question:2 - The silkworm is (a) caterpillar (b) a larva choose the correct option.

(i) a (ii) b (iii) both ‘a’ and ‘b’ (iv) neither ‘a’ nor ‘b’

Answer: (b) both 'a' and 'b'

Question: 3 - Which of the following does not yield wool?

(a)Yak

(b) Camel

(c) Goat

(d) Woolly dog

Answer: (d) Woolly dog

Question: 4 - What is meant by the following terms?

(a) Rearing

(b) Shearing

(c) Sericulture

Answer:

(a) Rearing: Taking care of animals including feeding, grazing, breeding, etc. for meat, and other useful products.

(b) Shearing –The removal of wool from the sheep is called shearing.

(c) Sericulture - The rearing of silkworm for obtaining silk is known as sericulture.

Questions: 5 - Give below is sequence of steps in the processing of steps in the processing of wool which are the missing steps? Add them.

Shearing _________ Sorting _________ _______________.

Answer: Shearing   Scouring  Sorting  Colouring   Spinning

Question: 6 - Make sketches of the two stages in the life history of the silk moth which are directly related to the production of silk.

Answer-

Question:7 - Out of the following which are the two terms related to silk production.silk production.

a. Sericulture

b. Floriculture

c. Moriculture

d. Apiculture and

e. Silviculture

Answer: (a) Sericulture and (b) Moriculture are related to silk production.

Question: 8 - Match the following

 

Ch 2 : Nutrition in Animals

                                                              Nutrition in Animals

 

Q -1 Fill in the blanks.
(a) The main steps of digestion in humans are _____ ____ _____ _____ ______

Answer - The main steps of digestion in humans are Ingestion digestion absorption assimilation egestion

b. The largest gland in human body is _______

Answer- The largest gland in human body is liver.

c. The stomach releases hydrochloric acid and _____ juices which act on food.

Answer- The stomach releases hydrochloric acid and digestive juices which act on food.

d. The inner wall of the small intestine has many finger like structure called _______.

Answer- The inner wall of the small intestine has many finger like structure called villi.

e. Amoeba digest its food in the ________

Answer – Amoeba digest its food in the vacuoles.

Q - 2 - Mark T if the statement is true and F if it is false.
a. Digestion of starch starts in the stomach.

Answer - F

b. The tongue helps in mixing food with sliva.

Answer - T

c. The gall bladder temporarily stores bile.

Answer - T

d. The ruminants bring back swallowed grass into their mouth and chew it for some time .

Answer - T

Q - 3 - Tick (√) mark the correct answer in each of the following.
a. Fat is completely digested in the
(a) Stomach
(b) Mouth
(c) Small intestine
(d) Large intestine

Answer - (c)Small intestine

b. Water from the undigested food is absorbed mainly in the
(a) stomach
(b) food pipe
(c) Small intestine
(d) Large intestine

Answer - (d)Large intestine

Q - 4 - Match the column

Q - 5 - What are villi? What is their location and function.

Answer - Villi is the finger like projections. These are found in the inner walls of small intestine. It helps in absorption of the digested food.

Q- 6 -Where is the bile produced? Which component of the food does it digest?

Answer - Bile is produced in the liver. Bile helps in digestion of fats.

Q -7- Name the type of carbohydrate that can be digested by ruminants but not by humans. Give the reason also.

Answer - Cellulose is the type of carbohydrates which is digested in ruminants but not in humans. Ruminants have a large sac –like structure between the small intestine and large intestine, in which cellulose of the food is digested by the action of certain bacteria. Such structure is not present in human. Hence human cannot digest cellulose while ruminants can.

Q- 8 - Why do we get instant energy from glucose?

Answer - Glucose is simple sugar so there is no need of digestion. It directly reaches the cells where it gives energy after respiration.

Q -9 - Which part of the digestive canal is involved in:
(a) Absorption of food ________
(b) Chewing of food ________
(c) Killing of bacteria ________
(d) Complete digestion of food _______
(e) Formation of faeces _________

Answer -

(a) Small Intestine

(b) Mouth

(c) Stomach

(d) Small Intestine

(e) Large Intestine

Q - 10 - Match the following column

 Q - 11 - Lable the diagram of the digestive system.

Ch 1 : Nutrition in Plants

                                                          Nutrition in Plants 

 

Fill in the blanks:

(a) Green plants are called _       autotrophs __ since they synthesize their own food.

(b) The foods synthesized by the plants are stored as starch .

(c) In photosynthesis solar energy is captured by the pigment called ___ chlorophyll

(d) During photosynthesis plants take in ____CO₂________ and release _ O₂

Name the following:

(i) A parasitic plant with yellow, slender, tubular stem.-------  Cascuta

(ii) A plant that has both autotrophic and heterotrophic mode of nutrition.---------  Insectivorous plants

(iii) The pores through which leaves exchange gases. ------- Stomata

(iv)  A plant that has both autotrophic as well as heterotrophic mode of nutrition. --- Pitcher plant.

(v)  An organism that live is an association of an alga and a fungus   ---------- lichen

(vi)  Amarbel is an example of: ----parasites  

(vii) The plant which traps and feeds on insects is----- pitcher plant

Match the items in column I with those in column II:

Chlorophyll ---–       Leaf.

Nitrogen   –––         Bacteria.

 Amarbel   –––      Parasite.

Animals   –––       Heterotrophs.

Insects  –––       Pitcher Plant

What is Nutrients?

Food is essential for all living organisms. Carbohydrates, proteins, fats, vitamins and minerals are components of food. The chemical substance present in components of food is necessary for our body and is called nutrients.

How humans and animals are are directly or indirectly dependent on plants.

All living organisms require food. Plants can make their food themselves but animals including humans cannot. They get it from plants or animals that eat plants. Thus, humans and animals

are directly or indirectly dependent on plants.

Why do we need food ?

Living organisms need food  to build their bodies, to grow, to repair damaged parts of their bodies and provide the energy to carry out life processes.

What is food ?

Food is the source of energy and every cell of an organism gets energy by the breakdown of glucose. The cells use this energy to carry out vital activities of life.

What is Nutrition?

Nutrition is the sum of all including taking food by an organism and its utilization by the body.

The mode of  nutrition in which organisms make food  themselves from simple substances is

called autotrophic nutrition. Ex plants.

The mode of nutrition in which organisms take in ready made food prepared by the plants

called heterotrophic nutrition. Ex animals

Whether food is made in all parts of a plant or only in certain parts?

Only certain part plant like leaves having green pigment chlorophyll. so Leaves are called  the food factories of plants.

Besides leaves, photosynthesis also takes place in other green parts of the plant — in green stems and green branches. The desert plants have scale- or spine-like leaves to reduce loss of water by transpiration. These plants have green stems which carry out photosynthesis.

How do plants obtain the raw materials from the surroundings?

Water and minerals present in the soil are absorbed by the roots and transported to the leaves.

Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. Such pores are called stomata. These pores are surrounded by ‘guard cells’

How do the raw materials transport them to the food factories of the plants?

Plants have pipe-like vessels to transport water and nutrients from the soil. The vessels are

made of special cells, forming the vascular tissue. The vascular tissue for the transport of water and nutrients in the plant is called the xylem. The vascular tissue for the transport of water and nutrients in the plant is called the xylem. Thus, xylem and phloem transport substances in plants

What is cell ?

The bodies of living organisms are made of tiny units called cells therefore Cell are called the building blocks of living organism.

Cells can be seen only under the microscope. Some organisms are made of only one cell. They are called Unicellular Ex. Amoeba, Paramecium etc

Living organism made up of many cells are called Multi cellular like man, tree etc

What is the cell membrane?

The cell is enclosed by a thin outer boundary, called the cell membrane Most cells have a distinct, centrally located spherical structure called the nucleus  The nucleus is surrounded by a jelly-like substance called cytoplasm.

What is tissue ?

A tissue is a group of cells that perform specialized function in an organism. For example, the vascular tissue for the transport of water and nutrients in the plant is called the xylem.

What are the main requirements of photo synthesis?

Chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of

Photosynthesis.

Explain the process of Photosynthesis?

Carbon dioxide from air is taken in through stomata. chlorophyll helps leaves to capture the energy of the sunlight. This energy is used to synthesize (prepare) food from carbon dioxide and water. Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis

Carbon dioxide +  water ---------sunlight/chlorophyll--àCarbohydrate  +    oxygen

Here the carbohydrates ultimately get converted into starch

How would you test the presence of starch on leaves?

Put 2-3 drops of dilute iodine solution on the leaves. Appearance of a blue-black colour indicates presence of starch in the leaves.

Why are leaves called the food factories of plants? Explain.

Leaves are called the food factories of plants due to following functions

ü  Green leaves have all the raw materials neccessary to carry the process of photosynthesis. 

ü  They have chlorophyll (green pigment) which captures the energy of sunlight. 

ü  Leaves consist of tiny pores called stomata on their surface. 

ü  Carbon dioxide from air is taken in through stomata. 

ü  Water and minerals are absorbed by the roots from the soil and transported to the leaves by vessels.

ü   

    Why sun is called the ultimate source of energy for all living organisms?

The solar energy is captured by the leaves and stored in the plant in the form of food. and this in turn use by other organism to get food to obtain energy Thus, sun is the ultimate source of energy for all living organisms.

Why algae are green in colour?

Algae contain chlorophyll which gives them the green colour. It can also prepare their own food by photosynthesis.

What are the main components presents in carbohydrates?

The main components presents in carbohydrates are carbon, hydrogen and oxygen.

From where do the plants obtain nitrogen?

Soil has certain bacteria  that convert gaseous nitrogen into a usable form and release it into the soil. These soluble forms are absorbed by the plants along with water.

By adding fertilizers rich in nitrogen to the soil farmers also made nitrogen available for plants

What is parasitic nutrition?

The mode of by which parasitic organism get and synthesize their food is called parasitic nutrition. Example Cucuta It does not have chlorophyll It takes readymade food from the plant

on which it is climbing. The plant on which it climbs is called a host.

How Pitcher plants get their nutrition?

There are a few plants which can trap insects and digest them. Such plants may be green or of some other colour. Such insect-eating plants are called insectivorous plants.

Example Pitcher plant

When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled into the hair. The insect is digested by the digestive juices secreted in the pitcher.

Why does the pitcher plant feed on insects though it is green? 

The pitcher plant does not get all the required nutrients especially those of nitrogen from the soil, hence it feeds on insects.

What is saprotrophic nutrition? What is the mode of nutrition in fungi?

This mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called saprotrophic nutrition. Plants which use saprotrophic mode of

nutrition are called saprotrophs. Example Fungi that secrete digestive juices on the dead

and decaying matter and convert it into a solution. Then they absorb the nutrients from it.

How do fungi appear suddenly during the rainy season?

Air generally consists of fungal spores. When these spores come in contact with warm things they germinate and grow. During rainy season, there are more chances of things getting wet.
Hence, fungi appear more in rainy season.

What do you under stand by symbiotic relationship present in some organism?

Some organisms live together and share shelter and nutrients. This is called symbiotic relationship . E.g. an alga, and a fungus live together fungus provides shelter, water and

Minerals to the alga and, in return, the alga provides food which it prepares by photosynthesis.

What is Symbiosis?

Symbiosis - It is the type of nutrition in which two different kinds of depend on each other for their nutrition. In this both the organisms are benefitted by each other e.g., lichen. In this one alga and one fungus live together and remain in symbiotic relationship.

How nutrients are replenished in soil?

Nutrients are replenished in soil by following ways

1.By  spreading manure or fertilizers that contain nutrients such as nitrogen in the fields

2.By  The bacterium Rhizobium that can take atmospheric nitrogen and convert it into a soluble form.

How do leguminous plants help replenishing soil fertility?

Rhizobium cannot make its own food. So it lives in the roots of gram, peas, moong beans

and other legumes and provides them with nitrogen. In return, the plants provide food and

shelter to the bacteria

Distinguish between a parasite and a saprotrophs

Parasite

1. A parasite takes readymade food from the organism on which it feeds.

2. They feed on a living organism.

3. The organism on which it feeds is called host.

4. It deprives the host of valuable nutrients.

saprotrophs

1. They secrete the digestive juices on the matter they live and convert it into a solution and then absorb it.

2. They feed on dead and decaying organism.

3. They do not feed on a living organism.

4. There is no host at all.

Why algae are green in colour?

Algae are green in colour as they contain chlorophyll which gives them the green colour. Algae can also prepare their own food by photosynthesis. Slimy, green patches in ponds or in other stagnant water  bodies are algae.