(i) nitric acid / potassium hydroxide solution is corrosive «and can burn the skin or damage the eyes» ✔

OR

the glass beaker / thermometer may break «and cut the skin» ✔

(ii) two straight lines drawn with a ruler: the rising line through «or close to» the points from 0.0 to 12.0 $\mathrm{cm^3}$ and the falling line through the points from 20.0 to 40.0 $\mathrm{cm^3}$, both extended until they cross «at about 17 $\mathrm{cm^3}$ and 34 °C» ✔

(iii) uncertainty in $\Delta T$ = «±»2 «°C» ✔

percentage uncertainty = «$\dfrac{2}{32 - 20} \times 100$ =» 17 «%» ✔

(iv) Any two of:

the specific heat capacity of the mixture is equal to that of water / 4.18 «$\mathrm{J\,g^{-1}\,K^{-1}}$» ✔

the density of the mixture is 1.00 «$\mathrm{g\,cm^{-3}}$» / 40.0 $\mathrm{cm^3}$ of mixture has a mass of 40.0 g ✔

no heat is lost to the surroundings / the heat capacity of the beaker and thermometer is negligible ✔

the reaction goes to completion / all the nitric acid reacts ✔

(i) [1] for any specific hazard: corrosive acid or alkali (accept 'burns' or 'irritates the skin or eyes'), broken glass, hot liquid. (ii) [1] for both lines passing close to their data points, not through the point at 16.0 cm3, and extended to the intersection; accept a rising line that takes the 16.0 cm3 point into account but passes above it; lines that are not straight or are obviously drawn without a ruler score zero. On screen, accept a description of the intersection, or its coordinates (about 17 cm3 and 34 °C), in place of drawn lines. (iii) M1: ±2 °C (two readings, each ±1 °C); M2: 17 % (accept 16.7 %, and 14 to 17 % if the temperature rise is read from the intersection of the lines). Award [2] for a correct final answer. (iv) [1] for each assumption, [2 max].