As we have learned in science class, most of our transportation is powered by fossil fuels.  When fossil fuels are burned, harmful greenhouse gases and pollutants are placed in the air.  Fossil fuels are considered to be non-renewable sources of energy, because they come from the remains of living things more than 300 million years ago that can in no way be replenished at the rate at which we humans are using them!  Therefore, we designed experiments to determine how best to propel rockets using Alka-Seltzer + water as a model of an alternative and renewable source of energy.

Before designing our experiments, we made some observations of other chemical reactions to get a better sense of how to design our own experiments.

As with every controlled investigation, we only change one variable in order to observe the effect(s) of that one change. Think back: What was the ONE variable that your group decided to change to the Alka Seltzer + water chemical reaction?  What is another way to describe the ONE variable that a scientist changes in an experiment?  What is another way to describe what the scientist measures?

Each group only changed one variable in order to see the effect(s) of that one change.  Some groups changed the temperature of the water or the amount of water, while other groups changed the size of the Alka-Seltzer tablet.  The group above changed the temperature of the water, and predicted that the hotter water would dissolve the tablet faster.

As a scientific community, we shared our group's results. Through our first round of experimentation, we learned that increasing the temperature, increasing the amount/volume of water, and crushing the Alka-Seltzer tablet all decreased the amount of time it took for the Alka-Seltzer to dissolve (for the chemical reaction to occur).

Before designing our rockets, we took a break and visited the animals!  What was your favorite animal at the Environmental Study Center?

After experimenting to better understand how the size of Alka-Seltzer, temperature and volume/amount of water affect the speed of the chemical reaction, each group picked one variable (= independent variable) to change to their Alka-Seltzer powered rocket to get the rocket that can propel the highest.  Most groups changed the temperature or size of the Alka Seltzer.  Do you remember which group had the highest rocket propulsion?  Do you remember this group's independent variable?

Last but most certainly not least, we learned that there is no such thing as failure in science.  There is also no such thing as an "incorrect" hypothesis, because the whole point of testing a hypothesis is to learn something new (and learning something new is never wrong/right/correct/incorrect).  Instead, we say that our hypothesis was "not supported" and reflect on the process and possible limitations that occurred in the planning/design and execution of the experiment, and also evaluate and possibly re-think our original hypothesis!

Take a look at the image on the left.  What do you observe?  A pair of eyes?  A nose?  A raccoon?

In reality, the image is a picture of a South African moth using "eye-spot mimicry".  Check out a picture of the moth taken from a different perspective here.  Surprised?

If your instinct was to try to guess what was "in" the image, you are not alone.  It is a very tempting response to the question, "What do you observe?".  However, as scientists, it is important that we understand the difference between what we observe, and what we infer. In this blog post, we will first learn about observations, the types of observations, and the relationship between observations and data.  We will then look into inferences, and how we can use our observations in order to make scientific inferences.

Observations

In reality, an observation is any information you can gather using the five senses and scientific instruments and tools.  In other words, what can we actually see, smell, taste, touch, hear, and measure in the picture?  There are two sets of concentric circles, the colors of burnt red, orange, white, and varying shades of brown, and symmetrical patterns and colors.

All observations are classified into one of two categories: qualitative observations and quantitative observations.  Qualitative observations describe the characteristics or qualities of something with words, such as color, odor, texture, sound, taste, etc.  Quantitative observations describe the measurement or quantity of something with numbers and a unit of measurement, such as "10 feet" or "150 grams".  Keep in mind that the unit is extremely important; it is the only part of the observation that actually tells us the meaning of that number.

When a scientist collects data, he/she is simply gathering and recording qualitative and quantitative observations.  Data describes all of the qualitative and quantitative observations that are collected as part of an experiment.  Some experiments involve making more qualitative observations, while others involve making more quantitative observations.  However, most experimental data is a combination of both qualitative and quantitative observations.  For example, scientists who are studying the effects of global warming refer to both qualitative and quantitative data.

Inferences

On the other hand, an inference is a logical conclusion based on observations and prior knowledge. "Based on my observations of the tomatoes, I can infer that the tomatoes are fresh because they are bright red, round, and shiny, and have a mass of 15.5 grams, which means that the tomatoes have a reasonably high water content."  In this example inference sentence, note how I incorporated both qualitative observations, quantitative observations, and prior knowledge in the "because" portion of the sentence.  Without this important "because", I would not be fully supporting my logical conclusion (inference).

Let's go back to our first picture example.  I can infer that the object in the image is a winged insect using "eyespot mimicry" because of the symmetrical patterns and colors, concentric circles, and soft appearance.  Again, note how the "because" portion of the inference is where I incorporated my observations and prior knowledge.

Below are example sentences to help you write your own scientific inferences:

• “I infer ___________________, because ________________________."
• “Because _________________, I infer __________________________.”
• “Based on my observations, I infer ________, because _____________.”

Check out the video below, created by Mr. Epp's science classroom.  When watching the video, keep in mind that the word "precise" means accurate and exact.

As scientists, it is very important that we understand the relationship between observations and inferences.  In order to make a scientific inference, we must consider all qualitative and quantitative observations before making any conclusions.  As we move into developing our own scientific investigations this school year, keep in mind that we will be collecting data (qualitative and quantitative observations) to develop our own scientific inferences and explanations of the phenomena we observe.