The gradient of a graph tells us how steep a line is. When we talk about the rate of a chemical reaction, the gradient of the graph can help us figure out how quickly the reaction is happening at a specific point in time.

Steps to Calculate the Gradient:

1. Draw a Tangent: Choose the point on the curve where you want to find the rate of reaction. Draw a straight line (tangent) that just touches the curve at that point.
2. Find the Change in Amount:

• Draw two vertical lines from the points where the tangent intersects the y-axis.
• The difference between these two points on the y-axis gives you the change in the amount of substance (this could be in grams, cm³, or moles, depending on what you're measuring).

3. Find the Change in Time:

• Draw two horizontal lines from the points where the tangent intersects the x-axis.
• The difference between these two points on the x-axis gives you the change in time (usually measured in seconds).

4. Calculate the Gradient: Use the formula:

This gives you the rate of reaction at the point where the tangent touches the curve.

Tangents are important because they let us measure the rate of reaction at a specific moment, not just the average rate over the entire reaction. This helps us understand how the reaction speed changes over time.