Heat

Question 1:What is the benefit of wearing bright coloured clothing in hot weather? Answer:Bright colours are poor heat absorbers, therefore we feel cooler. Question 2:What is the feature of the wall of a thermos flask that allows it to maintain the temperature of hot water for a long time? Answer:The shiny inner surface enables heat … Read more

Experiment 9.2:Aim: To study how a dark object absorbs and radiates heat better than a white object.Problem statement: Do dark objects absorb and radiate heat better than white objects?Hypothesis: Dark objects absorb and radiate heat better than white objects.A Good heat absorberVariables:(a) Constant variable: Distance from the heat source(b) Manipulated variable: Colour of surface(c) Responding … Read more

Question 1:What happens to the volume of water when it is heated? Answer:The volume of water increases. Question 2:Explain briefly why electric transmission cables on poles are hung loosely. Answer:The cable contracts when it is cold, so it will not cause any damages. Question 3:Will the expansion and contraction of matter be harmful to the … Read more

Activity 9.4:Aim: To show that heat can cause solid, liquid and gas to expand and contract.(A) SolidApparatus: Bunsen burner, gauge and metal barInstruction1. Try to fit the metal bar into the gauge (Figure 9.9).2. Heat the end of the metal bar using a Bunsen burner for five minutes.3. Try to fit the hot metal bar … Read more

Question 1:Why is the heating coil in an electric kettle placed at the bottom of the kettle? Answer:The heating of water begins around the coil of the heater. Hot water moves upwards and cold water moves downwards. This convection process enables the water to be heated faster. Question 2:The chicken that we roast in an … Read more

Experiment 9.1:Aim: To study the uses of different materials as heat insulators.Problem statement: Which is a good heat insulator, cotton, felt or aluminium foil?Hypothesis: Cotton and felt are good heat insulators.Variables:(a) Constant variable: Volume of water in the flat-bottom flasks(b) Manipulated variable: Types of insulators(c) Responding variable: Final temperatureMaterials: Cotton, felt, aluminium foil and boiling … Read more

Question:Aim: To show heat is transferred by conduction, convection and radiation.Materials: Candle wax, water, matches, candle, incense stick, potassium permanganate crystal and thumbtacksApparatus: Copper rod, beaker, wire gauze, bell jar, bulb, T-shaped cardboard, thermometer, tripod stand, retort stand with clamp and Bunsen burner(A) Conduction1. Stick three thumbtacks on a copper rod using candle wax and … Read more

Question 1:State the S.I. unit of heat. Answer:joule, J Question 2:Is the sense of touch a reliable method to determine if a person has fever? Give an explanation for your answer. Answer:No, sense of touch is not a reliable method to be used because the temperature cannot be observed in this manner. Question 3:Tick (√ … Read more