Year 7 – Skin, Bone, Muscle and Nerves

reaction_time_test

Your body consists of different systems that work together to provide nutrients, remove wastes, allow you to move, grow and reproduce. This term we will be studying the skeletal, muscular and nervous systems as well as the skin. These systems consist of organs, which are made up of tissues, which are comprised of cells.

The “Cell Theory” states that:
“Cells” are the smallest unit of life.
All living organisms are composed of cells and their products
All cells arise from pre-exisiting cells.

These cells are made up of organelles (nuclei, mitochondria, chloroplasts, golgi complexes, ribosmoes etc.). Organelles are made up of compounds (molecules) which consist of atoms. Atoms are known as the smallest indivisible particles.

So skin is made up of specific types of cells, different to muscle cells, bone cells and nerve cells. These different types of cells are different sizes and shapes and contain different nunmbers of organelles (a red blood cell has no nucleus for example) because they perform different functions within the body. Draw up a table in your workbook (or on your netbook) with the four different systems and describe their structure (what they look like) and function (how they work). Draw an example of the four different cell types in these systems. Use your textbook and research using the internet to complete your table.

Your first experiment will be about the nervous system – “How Quickly can you Respond to a Stimulus?”. Draw up the table in your books (or your netbook) and record your results from the experiment described on page 285. Compare your average in your writing hand with your non-writing hand. Then use your mobile phone to send a text message or play a game on your ipod while doing the same test.
What do you notice about the results?
What does this suggest to you about using a phone or ipod while driving?
Then try the same type of test at “The Online Reaction Time Test” page. See if you can beat my average reaction time of 0.273 seconds! Let me know in the comments section what your average reaction time for each experiment was.

What’s your pH? – Acids and Bases

red_cabbage

Creative Commons Image from Britt Gow

Learning Intention: To develop an understanding of acids and bases and the chemical reactions they are part of.

Success Criteria: You will be able to describe the differences between acids and bases and give several household examples of how they are used. You will perform some simple chemical reactions and identify that the  colour changes indicate the pH of the mixture.

Today we will be doing an experiment with acids and bases – making a pH indicator using red cabbage and testing various household substances. PH is a measure of the acidity (ph is less than 7) or alkalinity (ph is greater than 7) of a substance.

Another experiment we will do this week demonstrates how antacids work in your stomach. We will add dilute hydrochloric acid to a conical flask, which simulates the gastric juices in your digestive system. We will then add universal indicator to show the level of acidity. We will then add an antacid (alka-seltza tablet) and show how the pH increases, which demonstrates that the solution has become less acidic. When an acid and a base are mixed together the chemical reaction that takes place is called a neutralisation. The acid and base react to form a salt and water.

When metals are placed in acid they can corrode. An acid and a metal react together to produce hydrogen gas and a salt. You can test for hydrogen gas using the ‘pop’ test – light a match at the mouth of the test tube and you will hear a ‘pop’. Acid rain is problem in the northern hemisphere, caused by air pollution. We will learn more about acid rain in class.