A student carries out an experiment to determine the volume of 2 M sodium hydroxide needed to neutralise a known volume of 2 M hydrochloric acid.As different volumes of sodium hydroxide are added, the student uses a thermometer to measure the initial and final temperature. The change in temperature is then calculated.Which of the following options correctly identifies the variables in this investigation?I DON'T KNOWSUBMIT ANSWER

(c) The student repeats the experiment on a different day, using 25 cm 3of potassium hydroxide solution and 25 cm 3of dilute hydrochloric acid.The thermometer shows the highest temperature reached at the end of the experiment. °C 25 20(i) Complete the table by giving the missing information.Give both temperatures to the nearest 0.1 °C. (2) mean temperature at start in °C temperature at end in °C temperature rise in °C5.2

If you performed a similar experiment in the lab and used the following data to calculate the enthalpy of solution + neutralisation for sodium hydroxide. How many significant figures should you present your answer to? (Pay special attention to your value for temperature change, this may have fewer significant figures than you are expecting.) [1 mark]Volume HCl(aq): 40.0 mLVolume H2O: 60.0 mLMass of NaOH: 1.511 gInitial temperature: 20.5 oCFinal temperature: 29.9 oCQuestion 26Answera.3 significant figuresb.5 significant figuresc.4 significant figuresd.1 significant figuree.2 significant figures

(b) The table gives the temperatures of the solutions before the student mixes them. potassium hydroxide solution 17.8 °C dilute hydrochloric acid18.4 °CCalculate the mean (average) temperature of the two solutions. (2) mean temperature = .............................................................. °C(c) The student repeats the experiment on a different day, using 25 cm 3of potassium hydroxide solution and 25 cm 3of dilute hydrochloric acid.The thermometer shows the highest temperature reached at the end of the experiment. °C 25 20(i) Complete the table by giving the missing information.Give both temperatures to the nearest 0.1 °C. (2) mean temperature at start in °C temperature at end in °C temperature rise in °C5.2

. A company has made a new material called ‘Wellwarm’. They want to use ‘Wellwarm’ to make coats. (a) A scientist tested ‘Wellwarm’ to see how well it insulated a beaker of hot water. She tested ‘Wellwarm’ and three other materials as shown below. She wrapped each beaker in a different material. She recorded the temperature at the start and 20 minutes later. (i) What was the independent variable that the scientist changed? (ii) What was the dependent variable that the scientist measured during the investigation? (b) The results of the investigation are shown below. time (minutes) temperature of water (°C) wrapped in material A material B material C material D 0 60 60 60 60 20 34 40 38 36 material A material B material C material D thermometerlidPrimaryTools.co.ukPrimaryTools.co.uk KS3/09/Sc/Tier 3–6/P1 19 Total 8 9c 1 mark 9bii 1 mark 9c 1 mark 9d 1 mark 9e 1 mark (i) The scientist said that the ‘Wellwarm’ material is the best insulator. Which material was ‘Wellwarm’? Use the results to help you. Tick the correct box. (ii) Use the evidence in the results table to explain your choice. (c) The company made a coat from each of the four materials they tested. A person tested the different coats by wearing each one in a cold room. He measured the temperature inside each coat for 30 minutes. Write down two other variables that should be controlled to make this a fair test. 1. 2. (d) Write down one thing the scientists should do to make sure the person testing the coats is safe. (e) Suggest one advantage of using a temperature sensor and data logger instead of a thermometer in this experiment. maximum 8 marks 9bi 1 mark

In the core practical investigating the neutralisation of 50 cm3 of dilute hydrochloric acid with powdered calcium hydroxide, what measurement should you take first?The pH of the hydrochloric acidThe temperature of the hydrochloric acidThe mass of the calcium hydroxideThe pH of the calcium hydroxide2Calcium hydroxide powder is added to the beaker of 50 cm3 of dilute hydrochloric acid in increments of 0.3 g. What is the correct way to take a new pH measurement each time a further 0.3 g is added?Heat the beaker over a Bunsen flame before testing with universal indicator paper/solutionTake a small drop of solution from the beaker with a dropping pipette and place in a spotting tile before testing with universal indicator paper/solutionPour 10 cm3 of the solution from the beaker into a test tube before testing with universal indicator paper/solutionPlace universal indicator paper/solution directly into the beaker3When plotting the results of this practical on a graph, what should you put on the x and y axes?Volume of hydrochloric acid on the y axis, mass of calcium hydroxide on the x axispH on the y axis, mass of calcium hydroxide on the x axisMass of calcium hydroxide on the y axis, pH on the x axispH of the hydrochloric acid on the y axis, pH of the calcium hydroxide on the x axis4From the graph, what can you determine by drawing a horizontal line from pH7 to meet the graph and then drawing a vertical line down to the x axis?The volume of hydrochloric acid required to neutralise 0.3 g of calcium hydroxideThe temperature of the solution at the point of neutralisationThe mass of calcium hydroxide required to neutralise 50 cm3 of hydrochloric acidThe mass of calcium hydroxide that will dissolve in 50 cm3 of hydrochloric acid5What is the balanced symbol equation for the reaction that has taken place?CaCl2 + 2H2O → Ca(OH)2 + 2HClCa(OH)2 + HCl → CaCl2 + H2OCa(OH)2 + 2HCl → CaCl2 + 2H2OCaOH + HCl → CaCl + H2O