1. A student investigated the reaction between magnesium and excess hydrochloric acid Figure 1 shows the apparatus. Figure 1 This is the method used. 1. Pour 50cm^3 of hydrochloric acid into a conical flask. 2. Add a piece of magnesium 3. Insert stopper and delivery tube and start a timer. 4. Collect the gas produced in a gas syringe 5. Record the volume of gas produced every 20 seconds for 2 minutes. 6. Repeat steps 1 to 5 with higher concentrations of hydrochloric acid. (a) Give the independent variable and one control variable in this investigation. Independent variable __

Question

1. A student investigated the reaction between magnesium and excess hydrochloric acid Figure 1 shows the apparatus. Figure 1 This is the method used. 1. Pour 50cm^3 of hydrochloric acid into a conical flask. 2. Add a piece of magnesium 3. Insert stopper and delivery tube and start a timer. 4. Collect the gas produced in a gas syringe 5. Record the volume of gas produced every 20 seconds for 2 minutes. 6. Repeat steps 1 to 5 with higher concentrations of hydrochloric acid. (a) Give the independent variable and one control variable in this investigation. Independent variable __

Answer 1

Independent variable: Concentration of hydrochloric acidControl variable: Volume of hydrochloric acid

Answer 2

## Step 1:Identify the independent variable. The independent variable is the variable that is changed or controlled in a scientific experiment to test the effects on the dependent variable.## Step 2:In this investigation, the concentration of hydrochloric acid is varied. Therefore, the independent variable is the concentration of hydrochloric acid.## Step 3:Identify a control variable. A control variable is any other variable that is kept constant to prevent it from influencing the outcome of the experiment.## Step 4:One control variable in this investigation could be the volume of hydrochloric acid, which is kept constant at

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