Science Class 8 Reinforcement Worksheet

Transcription

1 Science Class 8 Reinforcement Worksheet Name: Sec: Date: Topic: Food And Digestion Q1. MCQs. A. Which juice is rich in iron? (a) Orange (b) Carrot (c) Apple (d) Mango B. Vitamin E is found in (a) Egg yolk (b) carrots (c) Mangoes (d) Milk C. Which of these is a rich source of Vitamin C? (a) A slice of cheese (b) A cup of orange juice (c) A medium baked potato (d) A piece of brown bread D. A rich source of protein is: (a) Fish meat (b) Cereal (c) Palm oil (d) Vegetables E. Fats simplify into: (a) Light oil (b) Fatty acids (c) simple sugars (d) Amino acids F. Digested food is absorbed through: (a) artery (b) Villi (c) Blood (d) Veins

2 Q2.Fill in the blanks. i) Main digestion of food takes place in the. ii) The involuntary wave like contraction by which food is moved through alimentary canal is called. iii) The function of large intestines is to absorb and mineral salt. iv) Fibre provides to keep intestines working properly. v) Enzymes are which speed up chemical reactions. Q3. Match Column A with Column B and write the correct alphabet in Column C. Column A Column B Column C Vitamin/Minerals Deficiency Problems Correct Alphabet 1. Vitamin A a. Rickets 2. Vitamin B1 b. Nerve degeneration 3. Vitamin C c. Anemia 4. Vitamin D d. High B.P due to excess of minerals 5. Vitamin E e. Night blindness 6. Vitamin K f. Beri Beri 7. Iodine g. Prolonged bleeding 8. Sodium h. Disease of bones 9. Iron i. Scurvy 10. Calcium j. Goitre Q4a. Distinguish between Physical and Chemical Digestion. PHYSICAL DIGESTION CHEMICAL DIGESTION b. If you eat a plain biscuit and chew it for longer period of time it tastes sweet. Explain why.

3 c. Fibre is not digested by human beings yet it is an essential part of a balanced diet. Justify. Q5. Look at the model of intestines below and answer the questions. a) What does these substances represent in the model? i) Visking tubing ii) Water iii) Starch and Glucose iv) Saliva Q6. A balanced diet includes carbohydrates, proteins and fats. (a) Name two natural (not processed) sources of dietary carbohydrate. (b) Give two uses of proteins in the body. (c) Explain how you would test for the presence of sugar in a food.

4 Q7. This diagram shows the digestive system in the human body. (a) Name parts A to F (not X or Y). (b) X is a gland below the mouth. What substance does X secrete? (c) Y is connected to the liver. What substance is stored in Y? (d) D contains a strong acid. What is the purpose of this acid? (e) What process takes place in B? Q8. This diagram shows a section through the walls of the small intestines. (a) What is the name of part A, and what is its purpose? (b) B is a blood capillary. Why are there blood capillaries in the walls of small intestines?

5 Q9a. A food contains protein. Describe what happens to this protein after the food reaches the stomach. b. Why doesn't the food enter the trachea instead of going to the esophagus? c. Name the enzyme that catalyses the digestion of dietary fats. d. What are the products of fat digestion? e. Name the substance produced by the liver that helps in the digestion of dietary fats. f. Explain how this substance helps in the digestion of dietary fats. Q10.This table shows the percentage of starch converted into maltose by a synthetic enzyme, amylase Q, under different conditions. Temperature ( C) Percentage of starch converted ph 3 ph 4 ph 5 ph 6 ph 7 ph a) What are the optimum conditions for Amylase Q? b) What is the effect of an increase in temperature on enzyme activity?

6 Q11. Complete the following. 1 Fish meat Amino acid 2 amylase 3 Fat fatty acid or 4 mouth saliva 5 Stomach digestion. 6 absorption villi Q12a. Suggest why fat is considered as a useful constituent of our daily diet? b. Mineral salts are required by our body in very small amount yet they are essential. Explain. c. What is the role of villi in the small intestines and how does its structure help it to perform its function. Topic: light Q1.a. Complete the diagram below by drawing and labeling the normal, the refracted ray and the emergent ray.

7 b. why straw appears bent when viewed from the air? c. explain why your face looks smaller when it is reflected on the outside surface of a shiny spoon. d. why are concave mirrors used in solar reflectors. e. what causes rainbow? f. draw a ray diagram to show how the light rays reach the observer. g. write mirror image of the following. 1. URGENT 2. AMBULANCE 3. MIRROR Q2. WRITE 3 EFFECTS OF REFRACTION. Give example for each. Q3.a. State the uses of plane, concave and convex mirror. b. which type of mirrors are used in telescope? c. what is the application of periscope and which type of mirrors are used? d. why a blue shirt appears blue in blue light but black under red light? ASSESSMENT SECTION A (15marks) Q1. Fill in the blanks. [8] 1. A shadow formed by an extended source of light consists of darker region called.

8 2. Angle of incidence is the angle between incident ray and the. 3. Light is a form of which can be detected by our eyes. 4. Speed of light in vacuum is. 5. Materials that are able to transmit almost all the light are called. 6. Digestive juice in stomach has a ph. 7. We can measure the ph values of substances quickly and accurately by using. 8. Front of the spoon is a surface. Q2. State whether the statement is true or false. Give correct statement for false statements. [4] 1. Concave mirror gives a magnified image. [ ] 2. Plane mirror has no use only placed in room for decoration. [ ] 3. Convex mirror gives virtual and diminished image. [ ] 4. White light is the combination black light and white light [ ] Q3. Name the phenomena of light in which: [3] 1. The light bends when travelling from one medium into another medium:. 2. The light is split into its components when pass through the prism:. 3. The light bounces back as it strikes a shiny and smooth surface:. SECTION B Q1. State characteristics of images formed by [2] 1. Convex mirror: 2. Concave mirror:

9 Q2. Define [2] 1. Diffused reflection. 2. Scattered reflection Q3. Define Reflection and also draw a diagram showing reflection. [5] Topic: heating and cooling Q1. State three effects of heat loss and heat gain. [3] Q1. Write down any 3 applications of expansion or contraction. [3] 1. 2.

10 3. Q3. Give reason and explain: 1. Why expansion is greater in solids than in liquids and gases? 2. Why mercury is used in thermometer?