The ECG

What is an ECG?
Have you watched television shows or movies where a patient in a hospital is attached to an electrocardiogram (ECG)? The ECG is a machine with a line moving across a screen that occasionally spikes or remains flat when a patient is dying. It is a recording of the small electric waves being generated during heart activity.

What makes the heart beat?
A normal heart beat is initiated by a small pulse of electric current. This tiny electric "shock" starts at the top of the heart and spreads down, and then up again, causing the heart muscle to contract in a way that has the pumping effect.

Where does the electricity come from?
In the heart, the pacemaker cells specialise in producing electricity.

~ Serena's Greenhouse

Interdependence Among Organisms

Organisms often depend on one another for survival. Some organisms form a close partnership with other kinds of organisms and these partnerships are called symbiotic relationships.

In the PSLE, pupils may be given a scenario based on symbiotic relationships. Using the information and contextual clues given, pupils must describe how two kinds of organisms are interdependent on each other.

Let's read about two examples of such symbiotic relationships.
(a) Cleaner Shrimps and fish
Cleaner shrimps and fish are interdependent on each other. As their name suggests, cleaner shrimps clean the fish.

The shrimps hang out at a cleaning station. When a fish stops by, a shrimp climbs onto the fish and sometimes even into the fish's mouth. The shrimp will use its tiny claws to pick tiny pieces of food off the fish's body. In the process, it helps to clean the fish by picking dead skin and tiny creatures that can hurt the fish.

(b) Plovers and crocodiles
Plovers are small birds that help to clean the teeth of the crocodiles. When a crocodile opens its mouth, the plover hops into the mouth. The crocodile does not snap its snout shut. Instead, it allows the plover to eat small, harmful animals attached to the crocodile's teeth.

How do they benefit from each other? The plover gets food while the crocodile gets its teeth cleaned.

~ Serena's Greenhouse

Recommended Reading List for Science

In the PSLE, there are some questions (Physical and Life Sciences) that will require pupils to apply Science concepts to everyday situations or phenomena around them. Parents and pupils have often approached me to recommend them some useful reading materials for Science. Pupils are encouraged to read widely so that they are more aware of how Science concepts are applied in everyday situations or certain gadgets, for example, bimetallic strips used in thermostat (popular question related to the P4 Topic on Heat in Top School Examination Papers).

Here are some books or magazines that pupils could read:
- My Pals Are Here Sciene PSLE Revision Guide
- My Pals Are Here Science Booster
- Talking Science Magazines
- Young Scientist Magazines
- Non-fiction books from the National Library Board on adaptations, symbiosis, etc

For younger kids, encourage them to read the Magic Schoolbus series to find out more about themselves and the world around them.
http://www.scholastic.com/magicschoolbus/books/index.htm

~ Serena's Greenhouse

Commonly Misspelt Words

As the school Preliminary Examinations are just round the corner, I thought it would be timely and useful to share with everyone some words that are commonly misspelt.

Commonly Misspelt Words in English - Spot the Mistakes!


- Seperate
- Definately
- Manover
- Occurence
- Unneccessarry
- Questionair
- Consience
- Curiousity
- Enviroment
- Beleive
- Arguement
- Embarassment
- Explaination
- Desribtion

Let's find out what the correct spelling should be...Commonly Misspelt Words in English - Spot the Mistakes! Usually I tell my pupils to think of a one-sentence story to remember the tricky words.

- Seperate            - Separate
- Definately          -  Definitely
- Manover   - Manoeuvre
- Occurence        - Occurrence
- Unneccessarry - Unnecessary
- Questionair - Questionnaire
- Consience           - Conscience
- Curiousity   - Curiosity
- Enviroment          - Environment
- Beleive             - Believe
- Arguement    - Argument
- Embarassment     - Embarrasssment
- Explaination - Explanation
- Decsribtion           - Description

Strategy
There are strategies to help with spelling. You can think of a one-sentence story to remember how to spell the tricky words. Try this strategy. My pupils have found it very useful.

Separate              -  I am sad to be Separated from my Pa (father)
Conscience  - Science has no conscience.

Search for commonly misspelt words on Google to learn more about them. Have fun!

~ Serena's Greenhouse

Digging "Gold" from our nostrils

Do your nostrils feel uncomfortable at times as there is "gold" (dirt) inside?All of us have to pick our nose to get rid of the "gold" in our nostrils.

How does it work?
The lining of our nostrils produces a sticky liquid called mucus. This mucus traps dust and germs in the air as we inhale. As the mucus dries up, it forms a gluey lining or a crusty layer inside the nostrils. In a nutshell, our nose helps to clean the air that enters our lungs.

~ Serena's Greenhouse

How do we determine if an egg is fresh?

Steps:

(1) Drop the egg in a glass of water and observe if it floats or sinks.

(2) A fresh egg will sink in water while an egg that is less fresh will float.

What Teacher Serena Says...
As the egg gets less fresh, the air space in the egg increases. Hence the egg becomes buoyant and floats.

~ Serena's Greenhouse

Cool Science in Seconds - Activity 1: Cartesian Diver

Cool Science in Seconds - Activity 1: Cartesian Diver 

Materials / Apparatus:
- A packet of condiment (ketchup / chilli sauce)
- A disposable mineral water bottle
- A glass of water

Steps:
(1) Test if your condiment packet is a good Cartesian diver. Fill a glass with water and drop the condiment packet into the glass. The best packets are ones that just barely float.

(2) Fill an empty, clear plastic mineral water bottle to the top with water. Drop your unopened condiment packet into the bottle. Cap the bottle.

(3) Squeeze the mineral water bottle to make the diver sink.  Release to make it rise.

Teacher Serena's Explanations:
This experiment demonstrates the property of buoyancy. Density is what determines whether an object sinks or floats. Density = Mass / Volume. The density of water is 1g /cm³

Many types of sauce are denser than water but it is the air bubble at the top of the sauce that determines whether the packet will sink or swim.

As the bottle is gently squeezed,  there is an increase in air pressure inside the bottle. The increase in air pressure is transferred throughout the bottle and causes the air inside the floating object to be compressed. In short, squeezing the bottle causes the bubble to shrink. This makes the floating object  denser and less buoyant. Hence it sinks.

Releasing the pressure on the bottle and the condiment packet begins to rise back to the top.

Applications in Real Life:

Fish keep themselves from either sinking or floating to the surface by using muscles to squeeze or relax a small sac (with a small air bubble inside) in their bodies. By squeezing the sac smaller, the fish will sink. By relaxing their muscles, the sac increases in size, displaces more water, and a fish will begin to rise to the surface.

Man use this same principle to control the buoyancy of a submarine. By pumping water in and out of tanks stored in the submarine, a submarine can be made to rise and sink. 

~ Serena's Greenhouse

Cool Science in Seconds

How does a submarine work? Why is there an "explosion" when we put Mentos in Coke?

Children get really excited when they conduct hands-on experiments to find out the answers to these questions and more. They enjoy conducting hands-on experiments to learn more about things around them. I have seen the joy and excitement on my pupils' faces whenever I conduct a Science experiment with them during Science lessons or Green Club CCA sessions.

I will be sharing with you some simple yet awesome experiments that you can conduct with your kids at home. Have fun!