Animation of the measurement of the effect of concentration of reactants on the rate of a chemical reaction. The conical flask at left contains hydrochloric acid in a one molar (1M) solution. The flask at right contains a four molar (4M) solution, which has four times the number of acid molecules in the same volume. At centre is a watch glass of magnesium ribbon pieces. When magnesium is added to the 1M solution, it reacts to form magnesium and chloride ions, and hydrogen gas. The gas is collected in a measuring syringe, and the volume is measured for sixty seconds. The process is repeated with the 4M solution. It is seen that this produces much more gas in the same amount of time. This is because there is more acid available to attack the magnesium.