Question

The flow rate of a liquid is related to the strength of the cohesive forces between molecules. The stronger the cohesive forces, the harder it is for the molecules to slide past one another. Honey is a very thick liquid that pours slowly at ordinary temperatures. A student tried an experiment. She filled five eyedroppers with honey at different temperatures and then measured the rate of dripping for each sample (see the table below). Graph the rate of dripping versus temperature for the honey and propose a relationship between temperature and flow rate. Propose an explanation for the trend that you observe.

Short answer

Flow rate increases with temperature; cohesive forces decrease as temperature rises.

Step-by-step solution

Understand the Experiment

A student conducted an experiment to investigate how temperature affects the flow rate of honey. The flow rate is measured by the rate of dripping from the eyedropper at different temperatures.

Collect Data

Review the provided data table, which shows the rate of dripping for honey at different temperatures. Note the temperatures and corresponding flow rates.

Plot the Data

On a graph paper or using a graphing tool, plot the temperature on the x-axis and the flow rate on the y-axis. Mark each point based on the data given (temperature, flow rate).

Draw the Best Fit Line

Analyze the plotted points and draw a line or curve that best fits the data points. This line or curve represents the relationship between temperature and flow rate.

Interpret the Graph

Observe the trend in the graph. Generally, as the temperature increases, honey flows more easily, which means the flow rate increases. This suggests that higher temperatures reduce the strength of cohesive forces between molecules in honey.

Propose a Relationship

Based on the graph, propose a relationship. For example, 'The flow rate of honey increases with increasing temperature.'

Explain the Trend

Provide an explanation for the observed trend. Higher temperatures provide energy to the honey molecules, reducing their cohesive forces and allowing them to slide past one another more easily, resulting in a faster flow rate.

Key concepts

Cohesive Forces

Cohesive forces are the attractive forces between molecules of the same substance. In the context of liquids, these forces play a crucial role in determining how easily the molecules can move past one another.
In honey, strong cohesive forces make it thick and viscous at room temperature, causing it to flow slowly. When you pour honey, these forces resist the movement of the honey molecules, making them stick together.
By experimenting with honey at different temperatures, we can see how these cohesive forces change and affect the flow rate of the liquid.

Temperature Effects

Temperature has a significant impact on the flow rate of liquids, including honey. When you heat a liquid, you provide more energy to the molecules, causing them to move faster.
In the case of honey, heating it decreases its viscosity because the added energy helps overcome the cohesive forces. This allows the molecules to slide past each other more easily, increasing the flow rate.
Conversely, cooling honey increases its viscosity by strengthening cohesive forces, making the liquid flow slower.

Experimental Graphing

Experimental graphing is a technique for visualizing the relationship between variables in an experiment. Here, we're interested in plotting the temperature of the honey against its flow rate.
To do this:

• Place temperature values on the x-axis.
• Put flow rate values on the y-axis.
• Mark each paired data point on the graph.

Once all points are plotted, you can draw a line or a curve that best represents the trend in data, helping to visualize how temperature affects the flow rate of honey.

Data Analysis

Data analysis involves examining and interpreting the collected data to understand trends and patterns. For this experiment, we look at how changes in temperature affect the flow rate of honey.
By plotting the data and drawing a best-fit line, we can identify a clear relationship. Typically, the graph shows that as temperature increases, the flow rate also increases.
This implies that honey flows faster at higher temperatures due to decreased viscosity, a result supported by analyzing the graphed data points.

Viscosity

Viscosity describes a liquid's resistance to flow. It depends on the internal friction between molecules, influenced primarily by cohesive forces.
Honey is highly viscous due to its strong cohesive forces. However, heating honey reduces its viscosity by weakening these forces, making it flow more easily.
Understanding viscosity is key to explaining why temperature changes affect the flow rate of honey. When the temperature rises, viscosity decreases, enhancing flow rate, and vice versa.