Understanding Diffusion: How Fast Does Tea Spread Through Water?

Tea is drunk by some almost daily to reduce stress, improve heart health, protect the cells in your body from damage...along with many more benefits! While waiting for the tea bag to sit in your water-filled cup, a process called diffusion occurs. In diffusion, molecules or ions move from areas of high concentration to areas of low concentration. The end goal is to reach equilibrium (when everything is evenly spread out). In this lab, we will look at how diffusion happens within a tea cup and the purpose of this experiment is to determine how temperature impacts the rate of diffusion.

How do you think water temperature changes the speed at which the tea color spreads (diffuses) through the water? State your hypothesis below.

1. Two 200mL beakers
2. Erasable Marker
3. Room temperature distilled water (acts as the "cold" water in this lab)
4. Hot water (Can be hot tap water or water boiled in a kettle, but make sure it’s hot enough to produce some steam for noticeable results!)
5. Thermometer (optional)
6. 2 tea bags
7. Timer

Gather all the supplies. Using an erasable marker, label one beaker “Hot” and the other “Cold” to avoid mixing them up during the experiment.

Fill the “Hot” beaker with 200mL of hot water and the “Cold” beaker with 200mL of room temperature distilled water.

If a thermometer is available, place the thermometer in both beakers for approximately 1 minute to measure its exact temperature. Ensure that the red tip of the thermometer is placed inside the water. Record the temperature difference.

If a thermometer is not available, skip to Step 4.

Take the tea bags out of their packaging. Place one tea bag in each beaker at the same time. Ensure both are fully submerged in the water before starting the timer.

Observe how the color inside the tea bag starts to spread into the water. Record what you see in the beakers at regular time intervals (0s, 30s, 1min, 2min, 3min, 4min, 5min) in the data collection sheet below.

While observing, pay attention to:

1. color change
2. How far the color has spread through the water
3. If the beaker is evenly coloured
4. How fast the color in the "Hot" beaker is spreading versus the "cold" beaker

At each time interval listed in the table, record your descriptions of the water’s appearance. Note both the color (transparent, light yellow, red-brown etc.) and the extent to which the tea color has spread through the water (slight color near the tea bag, halfway across the beaker, most of the beaker colored, evenly colored throughout etc.). In the "Even Color" column, indicate whether the color appears even by marking "Yes" or "No".

All living things are made up of cells, from humans and animals to plants, and even the tree in your backyard. To keep cells alive and for them to carry out their designated functions, substances must be able to move in and out of the cell's plasma membrane. This membrane is semi-permeable, meaning only selected substances can pass through. For instance, small molecules like oxygen passes through our cell membranes into our cells during respiration, and carbon dioxide moves out. Luckily, a natural process called diffusion is there to make this happen.

Diffusion is based on how much solutes there is in a certain area, meaning a substance that gets dissolved in a liquid. It is defined as the new movement of molecules or ions (the solutes) from an area of higher concentration to an area of lower concentration. The process of diffusion continues until equilibrium has been achieved, or in other words, when the solute concentration in both areas are equal. There are many variables that affect how fast the solutes move and spread out, which is the rate of diffusion. In this lab, we examined one of the most important variables: temperature. Ideally, the lab results should have revealed that the tea color diffused faster in the hot water than in the cold water.

1.What did you notice about the rate of diffusion in the hot water compared to the cold water? Based on your hypothesis, did it match with what you expected? Use evidence from the lab to support your claim, such as the temperature difference.

2.Compare the elelments of diffusion in a tea cup to the elements of diffusion in a real cell. How is the way tea spreads through the tea bag like how materials move in and out of our cells?

3.If you repeated this experiment using sugar instead of tea, would you expect similar results? Why or why not?