menu   Home About Me Home freebies My Store  
 photo 3am_AB_f1_zps652b0c0f.png    photo 3am_ab_gplus_zps3ab6fefc.png    photo 3am_ab_pin_zpsbfebd6d2.png    photo 3am_tpt1_zpse91e0740.png   photo 3am_ab_email1_zpsebc98a17.png

Search My Blog

Cells and pH

How do cells deal with changes in pH in their environment?

Many of the biochemical reactions that occur within cells produce end products that affect the pH of the cell.  Every cell has an optimum pH at which the cell will best function.  If the pH of the cell environment varies from the optimal pH too much, the cell could die.  It is vital that cells be able to manipulate their environment to maintain a pH of optimal functioning.  To accomplish this, cells produce buffers.  Buffers are substances that are either weak acids or weak bases that are produced in response to the cell becoming too acidic or too basic.

This concept is very easy to demonstrate to students.  To test this concept, I have the students first take a quantity of water and add drops of HCl acid, drop by drop, recording the pH after every drop.  They repeat using a new sample of water to which drops of NaOH are added.  This serves as a control, showing what happens to the pH when no buffers are being produced.

Next, the students test animal cells and plant cells to see if they can control the pH of their cell environment.  To a given quantity of liver homogenate (liver ground in the blender), students add the drops of acid and base and record the pH.  It is immediately obvious to the students that the cells are producing buffers to control their pH.  Repeating the process with raw potato proves that plant cells also produce buffers.

This is one of my favorite labs that I do with my Biology students.  It clearly shows the concept of buffers, it requires the students to use good lab techniques, the students must table large amounts of data, and the data must be graphed.  Much is accomplished by this lab!

If you are interested, here is a link to the lab I use:


Science Skills: The Compound Microscope



Is teaching a student how to properly use a microscope considered a "science skill"?
  
I think it is!

The regular followers of my blog know that I have been writing a series of articles on "Science Skills".  I think it is imperative that we teach our students skills that involved problem solving and critical thinking.  Don't get me wrong, the "facts" we teach in science are important too, but I have always found that if I do a great job in the "skills" area, the facts always fall nicely into place.


So the question of the day is:  Is having the student peer into a microscope considered a skill that teaches critical thinking and problem solving?  I say "YES",  but it will be up to the teacher to make the activity inquiry-driven and skills-based.  I think microscope work is important for the following reasons:

  • Students realize there is a "whole new world" out there.  Awareness of all environments will make our students better caretakers of the environment in the future.
  • It reinforces measurement skills.  Have students estimate the size of the microorganisms.  How does the size of one compare to another?
  • What impact does this microorganism have on other species?  Is the microorganism photosynthetic? If so, how will its disappearance from the aquatic ecosystem affect life on Earth?
  • Most students have not matured to the "abstract learner" stage.   Microscope work helps a student who is a concrete thinker by allowing them to "see, feel, and touch" things that are not normally visible to them.  You can show them plasmolysis occurring in a plant cell.  You can show them the chromosomes inside a cell.  You can show them sperm cells racing off to fertilize an egg cell.
  • You can teach cause and effect.  What happens when a cell is placed in this solution as opposed to that solution?
  • If nothing else... it is a great exercise for reinforcing hand-eye coordination!
Do you have some ideas about this topic?  How do you use the microscope to teach problem solving and critical thinking?  Let me hear from you by leaving a comment.

If you need some help getting started with teaching good microscope skills to your students, here are the materials that I use.

Quotes from Albert Einstein

Look at this face.....
What's not to love?

I am totally in love with Albert Einstein!  My classroom walls are full of posters with his pictures and quotes.


I find some of his quotes to be simply amazing, and they inspire me everyday as I try to help my students make sense out of the scientific world.   I thought I would share a few of my favorites:

"Two things are infinite: the universe and human stupidity; and I'm not sure about the universe." 
 Albert Einstein

"Insanity is doing the same thing, over and over again, but expecting different results." 
 Albert Einstein

"If you want your children to be intelligent, read them fairy tales. If you want them to be more intelligent, read them more fairy tales." 
 Albert Einstein

"The difference between genius and stupidity is; genius has its limits." 
 Albert Einstein

"When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That's relativity." 
 Albert Einstein

"I speak to everyone in the same way, whether he is the garbage man or the president of the university." 
 Albert Einstein

"Life is like riding a bicycle. To keep your balance, you must keep moving." 
 Albert Einstein

"Once you can accept the universe as matter expanding into nothing that is something, wearing stripes with plaid comes easy." 
 Albert Einstein

"Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid." 
 Albert Einstein

"What is right is not always popular and what is popular is not always right." 
 Albert Einstein

Science Skills: Significant Digits


Every year, the same great debate arises in our science departmental meetings .....  should we or should we not teach the rules of determining significant digits?  The members of the department have their reasons for being "pro" or "con" and it seems to me that the same people have the same reasons year after year.  Are we teaching significant digits because it is an important science skill, or just because it is found in the first chapter of the chemistry text book?

I tend to fall in the "pro" camp.  I think teaching significant digits is an important science skill to teach because:
  • It teaches the student the importance of making accurate and precise measurements.
  • It teaches the student how to look at the data in a scientific article and determine how accurate others have been in their measurements.
  • It teaches students how to learn a set of rules and then apply these rules to many examples.
  • It teaches critical thinking and problem solving skills.
  • It reinforces basic math skills when completing problems that involve calculations and rounding to a given number of significant digits.
  • It allows the opportunity to do a quick review on metric units.  (MANY kids need this!)
The people who think we should leave this out have pretty lame reasons (excuses) for their point of view:
  • It's boring.
  • Nobody needs to know this stuff any more.
  • It's archaic.
  • After you teach it in the first chapter, you never use it again.

The bottom line is that this is a tool of science, and for that reason, we need to makes sure our science students have this tool in their arsenal.  All research scientists know that there is "error" in their work.  The use of significant digits allows others a way of recognizing how much error exists in a set of measurements. 


Meanwhile, here are a few of the materials that I have developed and use as I teach significant digits.....I think it is still important!



Science Skills: Lab Equipment and Scientific Measurement




At the beginning of each new school year, it is essential that a science teacher instruct his/her students in the basic science skills.  This includes laboratory safety,  instruction in how the lab equipment operates, making proper scientific measurements, how to apply the scientific method, the importance of graphing and data analysis, and a review of basic math skills such as scientific notation.  I have already posted about several of these.  (See the posts below this one.)  Today, I want to emphasize the proper use of lab equipment and how to make scientific measurements.  

During a lab, a variety of tools may be used to allow the student to use an inquiry process to gather information, both qualitatively and quantitatively.  If the student is to reach the desired conclusion, it is imperative that they receive proper instruction on the use of the equipment they will be using. Scientists use a variety of tools to explore the world around them, and these tools are important to the advancement of science.  The tools may be simple or very complex.  One of the first labs I complete with my students is called:  Use of Lab Equipment and Data Analysis.  (You can download this one for free!)  It provides instruction on the basic pieces of lab equipment such as the meter stick, Celsius thermometer, graduated cylinder, and the quadruple-beam balance.  We teachers often assume that all students can use a meter stick, a graduated cylinder, a quad beam balance, and a thermometer, and that they can use all of these accurately.  This is not always true.  It is worth our time to spend one day in lab reviewing the proper use of these basic pieces of lab equipment.  After all, these tools will be used in our classes all year long.


When teaching the proper use of lab equipment, you must also give adequate instruction in how to make precise and accurate scientific measurements. I find that many students will need a short re-fresher on the metric system.  As for accuracy and precision in making measurements, it is the nature of the teenagers I teach to rush, rush, rush to get through with the experiments, giving little thought as to whether or not their data seems reasonable or logical.  If and when time allows, I often require my students to run multiple trials during an experiment to verify their results.  Unfortunately, due to the nature of a school setting, students have learned that science occurs in a 45 minute period of time, and that the first set of data is perfect and acceptable. We, as teachers, do what we can do with the schedule forced upon us by our schools, but you must try to give opportunities that require students to repeat and verify lab data.

Here are some of the materials that I have developed to help with the instruction and reinforcement of these basic science skills:

Free Lab:  Use of Lab Equipment

Lab: Making Metric Measurements (Length, Mass, Volume, and Temperature

Measurement Madness

Significant Figure Lab


Science Skills: The Metric System



Why do we continue to have to re-teach the metric system to our students every year?  I wish I knew the answer to this question!!  Students are exposed to and taught the metric system beginning in elementary grades, but they still need a refresher on it when they reach my high school chemistry class.  Why is this?  The reason is because a science class is the ONLY place that our students use the metric system.  While they may see references to it here and there, they never really use the metric system in their everyday lives.  Our students understand how many miles it is to the movie theater, but if you asked them how many kilometers to the movie theater, they will stare at you with a blank look.

In 1975, President Gerald Ford signed into law "H.R. 8674: Metric Conversion Act."  This law declared the metric system "the preferred system of weights and measures for United States trade and commerce." This law is ineffectual since it "permits the use of customary units in all activities."  Further, "all conversion was to be completely voluntary."  In other words, we have never converted to the metric system.  Our students haven't mastered the metric system because they do not use it except in our science classes.
Sure, the students know the basics of the metric system.  They know that length is measured in meters, mass is measured in grams and volume is measured in liters, but many of my students are still unsure as to how to convert one unit to another.  It is not unusual at all for one of my students to ask, "Which way do I move the decimal to convert ____ to ____?  Even more confusing is what to do with the units when determining area or volume.  How often have I heard, "Are these units squared or cubed?"

The manipulation of metric units must be reinforced at regular intervals, if for no other reason, than to just reinforce basic math skills.  Here's an example. Multiple the following:  (5 g/ml) (10 mL).  The answer?  50 g.  Many students will struggle when units are being added, subtracted, multiplied or divided. They can multiply 5 x 10, but they do not know what to do with the units.

What are we science teachers to do about this?  We have no choice but to teach, teach, teach! Your science class will go much smoother all year long if you will take a class period (or several!) at the beginning of the year to do a refresher on basic metric skills.

Here are a few resources in my TpT store that might be of some help to you:

Metric System Jeopardy Review Game

Metric System Bundle of 12 products

Metric System PowerPoint

Science Skills Mega Bundle

Metric System Task Cards

FREE Metric System BOOM Cards

Science Skills: Scientific Notation


In this series of blog posts, I have been writing about the importance of teaching "science skills" to our students.  (Previous posts include: Teach the Skills, Graphing Skills are Life Skills, and Applying the Scientific Method.)

The next skill that I would like to discuss is the proper use of scientific notation.  Scientific notation is used to express very small and very large numbers in a manner that makes problem solving easier.  Let's face it, chemistry students cannot enter Avogadro's number in their calculator unless it is in scientific notation.  In biology, viruses and bacteria are measured in nanometers and micrometers.  Both are simple examples of the need to use scientific notation in our science classes.

Many of the students entering my high school biology and chemistry classes are still struggling with how to write numbers in scientific notation.  Why is this?  I don't have the answer.  I worry that we are pushing middle school students to complete Algebra 1 and Geometry too early, and they are not getting the instruction they need in basic mathematics and arithmetic.

Whatever the reason, I find that I must spend a class period each year re-teaching this important skill.  Since my science classes use very large and very small numbers most every day, scientific notation is a must.  My students must be able to:
  • Write numbers in scientific notation.
  • Change numbers from scientific notion to standard form, and vice versa.
  • Add and subtract numbers that are in scientific notation.
  • Multiply and divide numbers that are written in scientific notion.
This is a much needed skill in a high school science class.  It is well worth the time to spend a class period reviewing and reinforcing these concepts.

The resources I use in my teaching can be found here:


Science Skills: Applying the Scientific Method


Teaching the “skills of science” is of the utmost importance.   I cannot stress this enough!  Yes, the "content of science" is important, but the content cannot be taught to our students until the skills are taught to our students. Scientific method, metric measurement, scientific notation, prefixes and suffixes, significant figures, compare/contrast, problem solving, critical thinking, dimensional analysis, proper use of lab equipment, scientific writing ... these are the skills I am referring to.  If the skills are taught properly at the beginning of the school year, your students will be equipped with the tools they need to be successful for the rest of the year.  Science is more than the memorization of a long list of facts.  Science is problem solving, analyzing, predicting and experimenting.  Make the teaching of basic science skills a priority in your class.

In a previous article, I talked about the importance of graphing skills.  Today, I want to talk about the importance of being able to apply the scientific method.  The key word here is...... apply.  You may be thinking, "I teach the scientific method every year during the first week of school."  Many teachers have their students write down the 5 or 6 steps to scientific method, define some keywords such as hypothesis, variable, and theory, re-state the 6 steps on a test, and .... DONE!  Time to move on to the next topic.  

We can do better than that.  Teaching our students how to apply the steps of the scientific method is not easy, and it takes up quite a bit of valuable class time.  We have to create lessons that teach the application of the scientific method, not lessons that teach the memorization of the scientific method.  

At the beginning of the school year we should give assignments that:
  • Reinforce graphing skills.
  • Teach students to interpret and analyze graphs.
  • Provide writing prompts to teach students how to design a controlled experiment.
  • Teach students to identify the independent and dependent variables in an experiment.
  • Teach students how to apply the scientific method to a particular scenario.
  • Give students practice in scientific writing.
Please get away from using only multiple choice, true and false, and matching questions.  I try as much as possible to have my students WRITE.  It is very time consuming to grade, but when students are asked "to design an experiment to show..." , you are teaching so many of the above skills.  And you are not just teaching the scientific method.  You are reinforcing critical thinking, problem solving, and best of all, good writing skills.

If you are just beginning to develop lessons on the scientific method, download my  FREE Scientific Method PowerPoint.  This is a 26 slide PowerPoint presentation on the nature of science and the scientific method.  The slides are colorful and visually appealing.  Steps of the scientific method are covered, but more importantly, the lesson provides examples and practice problems illustrating the application of the scientific method.  Analysis questions and answers are included.  The download also includes 4 pages of notes for the teacher and a 5 page outline of the notes for the student.  

Now take your students to the lab and see how well they can apply what they have learned about the scientific method.  My free "Can Your Students Write a Clear and Concise Procedure" is a great introduction into scientific writing. It's a fun activity that reveals to students the importance of accuracy and details when writing in science.  

Now you are ready to teaching students how to design and carry out a controlled experiment.  Start with this classroom activity (Applying the Scientific Method and Scientific Writing) involving hypothetical situations.  

Forge ahead with a student-designed lab activity:  The Scientific Method Lab. Students will plan and carryout the entire process from start to finish.  Full disclosure ... This takes time and quite a bit of patience, but it is worth it.  Your students will hone their problem solving and critical thinking skills as they complete these activities.