A learner investigated the ease with which various metal carbonates decompose on heating. She decided to heat equal masses of each carbonate and noted time how long it took for the carbon dioxide given off to turn lime water in a test-tube cloudy.

The control variable in this investigation is

Enzymes are biological catalysts. Purified enzymes are used widely both in research laboratories and in industry. Certain enzymes called proteases can hydrolyse proteins to amino acids. The amino acids can be separated and identified by chromatography. The diagram below shows a typical chromatogram.

${\mathrm{R}}_{\mathrm{f}} \mathrm{value} \mathrm{of} \mathrm{sample}=\frac{\mathrm{distance} \mathrm{moved} \mathrm{by} \mathrm{sample}}{\mathrm{distance} \mathrm{moved} \mathrm{by} \mathrm{solvent}}$

Sample A is _____

Enzymes are biological catalysts. Purified enzymes are used widely both in research laboratories and in industry. Certain enzymes called proteases can hydrolyse proteins to amino acids. The amino acids can be separated and identified by chromatography. The diagram below shows a typical chromatogram.

${\mathrm{R}}_{\mathrm{f}} \mathrm{value} \mathrm{of} \mathrm{sample}=\frac{\mathrm{distance} \mathrm{moved} \mathrm{by} \mathrm{sample}}{\mathrm{distance} \mathrm{moved} \mathrm{by} \mathrm{solvent}}$

The chromatogram must be exposed to a locating agent before the ${\mathrm{R}}_{\mathrm{f}}$ values can be measured. 

_____ is the difference chosen between consecutive values of the independent variable. (Interval/ Range)

The learner finds that the rate of a reaction is directly proportional to the concentration of a reactant, X.

Explain the quantitative relationship that the learner found in this investigation using your scientific knowledge and understanding.

Enzymes are biological catalysts. Purified enzymes are used widely both in research laboratories and in industry. Certain enzymes called proteases can hydrolyse proteins to amino acids. The amino acids can be separated and identified by chromatography. The diagram below shows a typical chromatogram. 

${\mathrm{R}}_{\mathrm{f}} \mathrm{value} \mathrm{of} \mathrm{sample}=\frac{\mathrm{distance} \mathrm{moved} \mathrm{by} \mathrm{sample}}{\mathrm{distance} \mathrm{moved} \mathrm{by} \mathrm{solvent}}$

_____ hydrolysis leads to amino acids. 

The type of graph used to display the results of how different transition metal oxides affect the rate of a reaction is a _____ chart. (bar/ dot/area)

To find rate of a precipitation reaction, the concentration of a reactant is taken as  $0.2, 0.4, 0.6, 0.8$ and $1.0 \mathrm{mol} {\mathrm{dm}}^{-3}$.  What is the range and interval value respectively?

Enzymes are biological catalysts. Purified enzymes are used widely both in research laboratories and in industry. Certain enzymes called proteases can hydrolyse proteins to amino acids. The amino acids can be separated and identified by chromatography. The diagram below shows a typical chromatogram.

${\mathrm{R}}_{\mathrm{f}} \mathrm{value} \mathrm{of} \mathrm{sample}=\frac{\mathrm{distance} \mathrm{moved} \mathrm{by} \mathrm{sample}}{\mathrm{distance} \mathrm{moved} \mathrm{by} \mathrm{solvent}}$

Ninhydrin test can be used to identify amino acids.

In an experiment to find the enthalpy change of a reaction between two solutions, the mass of solutions mixed together was $50.0 \mathrm{g}$ and the temperature increased by $7.5°\mathrm{C}$. The specific heat capacity of the solutions was taken as $4.18 \mathrm{J} {\mathrm{g}}^{-1}°{\mathrm{C}}^{-1}$.

The energy transferred in joules ($\mathrm{J}$) is