Experiment 23 Factors Affecting Reaction Rates Pre Lab Answers

Start with a fizz — and a question

Picture this: you drop a tablet into a glass of water and watch it dissolve faster than it should. Or you leave a cut apple on the counter and come back an hour later to find it browning. These aren’t just everyday observations — they’re the raw material of chemistry. And in a pre-lab setting, they become the starting point for Experiment 23: Factors Affecting Reaction Rates.

This experiment isn’t about memorizing formulas or copying data tables. What changes when I tweak this variable?Consider this: it’s about learning to ask: Why does this happen? * The pre-lab questions aren’t busywork — they’re your chance to think like a scientist before you even touch a beaker.

Let’s break down what those pre-lab answers should really be getting at.

What Experiment 23 Is Really Testing

At its core, Experiment 23 is about one fundamental idea: reactions don’t all happen at the same speed. Some are over in a flash. Others crawl along like molasses in January. The goal of the experiment is to systematically test which factors influence how fast a reaction occurs.

The classic setup usually involves a simple, observable reaction — often something like the decomposition of hydrogen peroxide catalyzed by catalase (found in potatoes or liver), or the reaction between sodium thiosulfate and hydrochloric acid, where you can track the formation of a precipitate. The key is that the reaction produces a visible change you can measure: gas bubbles, color change, cloudiness, or time until a cross drawn under the beaker disappears.

The pre-lab questions are designed to make you think about the science behind the setup before you start mixing chemicals. They’re asking you to consider not just what* you’re doing, but why you’re doing it — and what you expect to see.

Why Reaction Rates Matter (Beyond the Lab)

Understanding reaction rates isn’t just academic. It’s the difference between a medicine that works and one that degrades on the shelf. It’s why food spoils, why engines run efficiently, and why some materials last decades while others crumble in months.

In the lab, if you don’t grasp the variables at play, your results become noise. Now, you might think temperature doesn’t matter — until you run the same reaction at 20°C and 40°C and watch one finish in minutes while the other takes hours. Or you might assume concentration is the only thing that counts, missing the fact that surface area can be just as powerful.

The pre-lab is your insurance policy against running experiments blindly. It forces you to form hypotheses, predict outcomes, and identify what you’re actually measuring. On top of that, without that foundation, you’re just following steps. With it, you’re doing science.

How the Five Key Factors Actually Work

There are five main variables that consistently show up in reaction rate experiments. Each one operates through a slightly different mechanism — and each one should be addressed in your pre-lab thinking.

Temperature: More Energy, More Collisions

Once you increase temperature, you’re not just making things hotter. You’re giving molecules more kinetic energy. They move faster, collide harder, and — crucially — more of them have enough energy to overcome the activation energy barrier.

Think of activation energy as a hill molecules need to climb to react. At higher temperatures, more molecules are rolling fast enough to get over that hill. The result? Plus, a faster reaction. In your pre-lab, you should predict that the reaction at a higher temperature will proceed noticeably quicker — often dramatically so.

Concentration: More Particles, More Opportunities

Higher concentration means more reactant particles packed into the same volume. That increases the frequency of effective collisions. It’s like adding more people to a conversation — the chances of two people saying the right thing at the right time go up.

In the pre-lab, you should expect that doubling the concentration of a reactant will increase the reaction rate — though not always by exactly double, because other factors can become limiting. The key insight is that concentration directly affects how often particles collide.

Surface Area: Breaking It Down to Speed It Up

This is the factor that trips up a lot of students. When a solid reactant is broken into smaller pieces, you’re exposing more of its surface to the other reactant. More surface area = more sites for collisions to occur.

A great example: a whole potato cube in hydrogen peroxide will react slowly. Grated potato? On top of that, the reaction is visibly faster. In your pre-lab, you should predict that increased surface area leads to a faster initial reaction rate, and you should be ready to explain why — it’s about exposing more active sites, not changing the chemistry itself.

Catalysts: The Shortcut Providers

A catalyst doesn’t get consumed in the reaction. Instead, it provides an alternative pathway with a lower activation energy. It’s like building a tunnel through the hill instead of making molecules climb over it.

In many versions of Experiment 23, a biological catalyst like catalase (from potato or liver) is used. Your pre-lab should identify the catalyst, predict that it will speed up the reaction without being used up, and explain that it works by lowering the energy barrier.

Agitation or Stirring: Keeping Things Mixed

This one is subtle but important. Which means stirring doesn’t change the inherent speed of the reaction — but it keeps fresh reactants in contact with the reaction zone and removes products that might slow things down. In heterogeneous reactions (where reactants are in different phases), stirring can dramatically improve the rate by ensuring continuous contact.

In your pre-lab, if stirring is part of the procedure, you should predict that it will maintain or increase the reaction rate over time, especially in reactions involving solids and liquids.

Common Mistakes Students Make in the Pre-Lab

Here’s what I see every semester: students treat the pre-lab like a checklist instead of a thinking exercise.

One of the most common errors is confusing rate* with amount*. Day to day, a reaction might produce the same total amount of product regardless of temperature — but it gets there faster at higher temperatures. The pre-lab should distinguish between how fast something happens and how much happens overall.

For more on this topic, read our article on phil ivey and the wager by david grann or check out what is the central idea of the text.

Another mistake is assuming all factors have the same effect. Because of that, concentration and temperature don’t work the same way. Surface area doesn’t behave like a catalyst. Each factor has its own mechanism, and your pre-lab should reflect that understanding.

Students also forget to consider control variables. If you’re testing temperature, you need to keep concentration, surface area, and catalyst amount constant. The pre-lab is where you lay that out — explicitly stating what you’re changing and what you’re keeping the same.

And here’s a big one: not making specific, testable predictions. Saying “the reaction will be faster” isn’t enough. You should predict how much* faster, or at least describe the observable difference you expect to see.

What Actually Works in Pre-Lab Preparation

Start by reading the procedure carefully — not just skimming it. Then ask yourself: what am I actually measuring? On the flip side, time? Volume of gas? Clarity of solution? The measurement method determines what kind of data you’ll collect, and that shapes your predictions.

Write down your hypothesis for each factor in plain language. Don’t just say “rate increases.” Say why you think it increases, and how you expect to observe that increase in the lab.

Sketch a quick mental model of what’s happening at the molecular level for each variable. Practically speaking, surface area means more exposed sites. Temperature means faster molecules. Think about it: concentration means more molecules. Because of that, catalysts mean a lower energy path. Agitation means better mixing.

And here’s something most students skip: think about what could go wrong. If it’s too slow, you might be waiting forever. Here's the thing — if your reaction is too fast, you might miss the start time. Anticipating these practical issues in the pre-lab makes the actual experiment run smoother.

FAQ

What is the purpose of Experiment 23 on reaction rates?
The purpose is to identify and test the five main factors that influence how fast a chemical reaction occurs: temperature, concentration, surface area, catalysts, and agitation. The pre-lab phase helps you form hypotheses and understand the underlying science before conducting the experiment.

How does temperature affect reaction rate in this experiment?
Higher temperature increases the kinetic energy of molecules, leading to more frequent and more energetic collisions. This means more molecules have enough energy to overcome the activation energy barrier, resulting in a faster reaction rate.

Why is surface area important in reaction rate experiments?
Increasing the surface area of a solid reactant exposes more particles to the other reactant, creating more sites for

Increasing the surface area of a solid reactant exposes more particles to the other reactant, creating more sites for effective collisions and therefore accelerating the overall reaction. In practice, this means that a powdered solid will react noticeably faster than an equivalent mass of larger chips, because the powder provides a greater number of reactive interfaces.

Additional FAQ Highlights

How does agitation (stirring) influence the reaction rate?
Agitation ensures that reactants are continuously brought into contact with one another, reducing concentration gradients that can develop as the reaction proceeds. By keeping the mixture uniform, stirring eliminates “dead zones” where the reaction would otherwise slow down, leading to a more consistent measured rate.

What role does the catalyst play in this experiment?
A catalyst provides an alternative reaction pathway with a lower activation energy, allowing a larger fraction of molecular collisions to be successful without being consumed. In the lab, this typically manifests as a dramatic speed‑up that can be quantified by comparing the time to reach a predefined endpoint with and without the catalyst present.

Why is it important to record the exact temperature of the reaction mixture?
Temperature fluctuations can introduce variability that masks the effect of the variable you are testing. By logging the temperature continuously (or at least before and after the reaction), you can correlate any observed rate changes directly to temperature rather than to unnoticed thermal drift.

Putting It All Together

The moment you sit down to write your pre‑lab notes, treat the experiment like a miniature research project. Start with a clear statement of the problem: How do temperature, concentration, surface area, catalysts, and agitation each affect the rate of this specific reaction?* Then, for each factor, outline:

The underlying molecular rationale – e.g., higher temperature raises kinetic energy, more frequent collisions, and a greater proportion exceeding the activation barrier.
The measurable outcome – time to collect a set volume of gas, disappearance of a color, or mass loss, depending on the reaction’s signature.
A quantitative prediction – “At 40 °C the reaction should complete in 45 seconds, compared with 90 seconds at 20 °C.”
Control variables – list everything you will keep constant (e.g., initial concentrations, catalyst mass, stirring speed) to make sure any observed change is truly due to the factor under study.
Potential pitfalls and contingencies – note if the reaction might be too fast for manual timing, or if the gas collection apparatus could leak, and propose solutions (use a stopwatch with a photogate, add a water trap, etc.).

By walking through these steps, you transform a routine lab exercise into a disciplined investigation. The pre‑lab becomes a roadmap that not only guides you through the practical steps but also reinforces the conceptual framework linking molecular behavior to macroscopic observations.

Final Take‑away

A well‑crafted pre‑lab isn’t just a checklist; it’s the bridge between theory and experiment. When you enter the lab with this clarity, you’ll move faster, make fewer mistakes, and gain deeper insight into the chemistry at work. It forces you to think critically about why each variable matters, how you will measure its effect, and what* you expect to see. In the end, the most successful experiments are those where preparation meets curiosity, turning a simple demonstration into a memorable discovery.