## Investigating a Change in Temperature

• To measure the effect of temperature on the rate of reaction between sodium thiosulphate and hydrochloric acid
• To consider fair testing and accuracy in my method
• To justify why increasing the temperature increases the rate of reaction

# Reaction of Sodium Thiosulphate and $HCl$

• On Thursday you will be reacting these chemicals together. Sodium thiosulphate has chemical symbol $Na_{2}S_{2}O_{3}·5H_{2}O$ and hydrochloric acid $HCl$.
• Both are clear liquids and when mixed together the solution goes cloudy over a period of time.
• By measuring the time until the black cross is no longer visible, you can determine the relative rate of reaction.

## Whakamātau Groups

### Step 1: Aim & Hypothesis

2. Come up with an aim (what are you investigating; be specific)
3. Come up with a hypothesis (what do you predict; be specific)

### Step 2: Variables

• Independent Variable: The variable that you will change. What are we changing? Include units, measurement apparatus & range of measurements.
• Dependent Variable: The variable being measured. What are you measuring? Include units & measurement apparatus.

### Step 3: Control Variables & Reliability

• Control Variable: Things that you are keeping constant. What will you not change throughout your whakamātau?
• Reliability: An whakamātau is reliable if the results are within x seconds of each other when the method is repeated. The same method must give the same results each time.

### Step 4: Method

• Give you method as a numbered list,
• List what equipment you will need (e.g. a 100ml beaker; 25ml of diluted $HCl$),
• Break things up into small steps and say when you repeat a set of steps,

### Step 4: Continued

• State your range of measurement for your independent variable, its units and how you will measure it,
• States some control variables and how to control them during the whakamātau.

### Step 5: Data/Results

• Design a table to record your results before you start the whakamātau,
• You will need to think about how many trials you are going to do, how many measurements you will make and calculating an average.

Trial 1Trial 2Trial 3Average
Temp 1 ($10^{\circ}C$)
Temp 2 ($20^{\circ}C$)
Temp 3 ($30^{\circ}C$)
Temp 4 ($40^{\circ}C$)