Homework 1 Particle model and density answers Homework
- Slides: 26
Homework 1 Particle model and density answers
Homework 1 answers 1. Table: 2. 35 / 0. 043 = 814 kgm² (3) • 1 × 10 -5 m³ • 5 × 10 -5 m³ • 0. 000175 m³ 3. 70 / 0. 5 = 140 kgm² (3) 4. 1000 / 15 = 67 kgm² (3) • 0. 00055 m³ • 0. 01 m³ Total marks: 14 marks
Homework 1 answers 5. Method: Regular object • Use ruler to measure the length width and depth of the shape. • Use these to calculate the volume in m 3. • Place object on weighing balance and record mass in kg. • Divide the mass by volume to get the density for the object Total marks: 4 marks
Homework 1 answers 6. A substance’s mass per unit volume 7. 8. Strong forces of attraction hold the particles close together in a regular arrangement 9. Weaker forces of attraction between the particles, in an irregular arrangement so can move past each other 10. Almost no forces of attraction between the particles so spread far apart Total marks: 5 marks
Homework 1 answers 11. 0. 02 m 3 12. 13. 6 kg 13. Complete the table: Object W X Y Mass (kg) 5000 20 000 18000 Volume (m 3) 2 5 6 Density (kg/m 3) 2500 4000 3000 Z 10 000 20 5000 Total marks: 6 marks
Homework 1 answers 14. Tungsten 13. 6 g/cm 3; Wolfram 13. 6 g/cm 3. Both are the same 15. V=120 cm 3; m=156 kg. 16. V=2000 cm 3; p=1. 6 g/cm 3. 17. 7700 g; 7. 7 kg Total marks: 4 marks
Homework 1 - extension 1 answer Method: Irregular object • Place irregular object on weighing balance to record the mass • Fill a eureka can with water up to the spout. Place a measuring cylinder next to the spout to collect any water. • Place irregular object in eureka can. Measure the volume of the displaced water in the measuring cylinder. Record this volume. This is the volume of the irregular object • Density = mass/volume Total marks: 4 marks
Homework 1 - extension 2 answer Density is mass per unit volume and the particles in solids are very close together. They are tightly packed, giving solids high densities. (2) Total marks: 2 marks
Homework 2 Cooling curve answers
Homework 2 answers 1. A cooling curve is a line graph that represents the change of phase of matter, typically from a gas to a solid or a liquid to a solid. The independent variable (X-axis) is time and the dependent variable (Y-axis) is temperature (2) 2. Diagram: (3) 1. Converting from one state to another usually involves heating or cooling. Heat must be supplied to a substance for it to melt and heat must be removed from a substance to condense or freeze it. (3) Total marks: 8 marks
Homework 2 extension 1 Total marks: 4 marks
Homework 2 extension 2 Total marks: 4 marks
Homework 3 Internal heat energy and specific heat capacity answers
Homework 3 answers 1. The particles move at a range of speeds (1) in different (random) directions (1). As the balloon warms and expands its density of the helium decreases. The balloon at some point has the same density as the air around it, eventually the balloon becomes less dense that the surrounding air and floats up to the ceiling. (3) 2. The temperature of an object relates to both the kinetic energy of its particles and the number of particles. It is measured in °C and is how hot or cold a substance is. (2) 3. Heat is a form of energy. It is measured in Joules. It relates to kinetic energy which causes the particles in an object or substance to vibrate (2) 4. Internal energy is the sum of potential and the sum of kinetic energy in a system (1) Total marks: 10 marks
Homework 3 answers 5. • Increase in temperature • Particle size • Concentration • Catalyst One gram of Water takes a fixed amount of energy to rise in temperature by 1 degree. Twice the amount takes twice the energy. Total marks: 5 marks
Homework 3 answers 6. Specific heat capacity required practical method: • Place the immersion heater into the central hole at the top of the block. • Place thermometer into the smaller hole and put a couple of drops of oil into the hole to make sure thermometer is surrounded by hot material. • Fully insulate the block by wrapping it loosely with cotton wool. • Record the temperature of the block. • Connect the heater to the power supply and turn it off after ten minutes. • After ten minutes the temperature will still rise even though the heater has been turned off and then it will begin to cool. Record the highest temperature that it reaches and calculate the temperature rise during the experiment. Continued on next page
Homework 3 answers Record results in a suitable. The example below shows some sample results. Ammeter reading (A) 3. 65 Voltmeter reading Initial temperature (V) (°C) 10. 80 15 Final temperature (°C) 38 Analysis The block has a mass of 1 kg and the heater was running for 10 minutes = 600 seconds. Using the example results: energy transferred = potential difference × current × time Continued on next page
Homework 3 answers Total marks: 6 marks
Homework 3 answers 7. • Mass of water = 2 kg • Specific heat capacity of water= 4200 J/kg ºC. • Temperature change = 30 – 20 = 10ºC • Energy needed = 2 × 4200 × 10 = 84000 J (84 k. J) Total marks: 3 marks
Homework 3 answers 8. E = 3 kg x 1000 J/kg°C x 10 = 30000 J 9. E = 0. 5 kg x 4200 x 2 = 4200 J 10. E = 2 x 10 x 5 = 100 J 11. SHC = 100 J / 1 x 1 = 100 J/kg. Deg. C Total marks: 12 marks
Homework 3 extension answers 12. Mass = 160, 000/(4200 x 75) = 0. 51 kg or 510 g 13. Mass = 2500/(2400 X 11) = 0. 095 kg or 95 g 14. Δ°C = 500/(0. 025 X 2000) = 10 °C Total marks: 9 marks
Homework 3 extension answers 15. Δ°C = 2, 000/(124 X 1000) = 16. 1 °C 16. E = 0. 003 X 390 X 40 = 46. 8 J Total marks: 6 marks
Homework 4 Latent heat energy answers
Homework 4 answers 1. Eh = ml 0. 60 × 199 000 = 119 400 J Total marks: 3 marks
Homework 4 answers 2)a)i) liquid ii) liquid b)i) 110°C ii) X should be between 110 and 440°C (on the line between 3 and 5. 8 seconds) Y should be on the flat line at 110°C (between 0. 6 and 2. 8 seconds) iii) the time it is melting for is 2. 2 seconds. Energy is 100 J every second. 100 x 2. 2 = 220 J of energy to melt substance iiii) Specific latent heat= energy /mass = 220 /1. 5 = 146. 7 J/Kg 3)a) Specific Latent Heat , Fusion b) Specific Latent Heat , Vaporisation c) bonds , more d) J/kg , 1 , liquid , temperature Total marks: 21 marks Continued on next page
Homework 4 answers 4) When 100 degree water touches your hand it cools and releases energy, this energy can be calculated using the specific heat capacity. (1) When 100 degree steam touches your hand, the steam condenses and changes into a liquid; it releases the latent heat of vaporisation. (1) It then cools releasing the same energy as the water. This means that the steam releases more energy. (1) 5) Specific latent heat= energy /mass = 2000 x 120 /0. 09 = 240, 000 / 0. 09 = 2 670 000 J/Kg (3) Homework 4 extension mark scheme on a separate sheet attached Total marks: 6 marks
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