CLASS 8TH DAY 1
INTRODUCTION
Measures of Central Tendency
In this lesson, we’re looking at the measures of central tendencies.
The measures of central tendency provide us with statistical information about a set of data. The four primary measurements that we use are the mean, median, mode and range. Each one of these measurements can provide us with information about our data set. This information can then be used to define how the set of data points are connected.
Let’s watch the following video to learn more about Mean, Mode & Median.
Here is a small quiz to test your understanding. Try to attempt all the questions and get the highest marks possible.
Experiment: Compost in a Bottle
This experiment will demonstrate the decomposition process and simulate the breakdown of organic matter into compost.
What is Decomposition?
Decomposition is the process by which a material is broken down into simpler parts. Composting is a great example of the decomposition process.
Why compost?
Composting organic matter has a number of environmental benefits:
- Is a great way to recycle nutrients into your soil- you will save on fertilisers;
- It will reduce evaporation from your soil- saving you water;
- It produces minimal amounts of methane (a greenhouse gas), unlike landfilling; and
- It saves on transporting your waste away from your house to the landfill.
How does compost work?
Compost relies on four main ingredients:
- Carbon material (dry leaves, paper and newspaper);
- Nitrogen material (grass clippings, food scraps);
- Water; and
- Air.
Once combined, these ingredients attract bacteria and fungi, which start to feed on the organic matter. As they feed and multiply, they produce heat as a by-product. This heat also helps the decomposition process. Air and oxygen mix through the compost allowing the bacteria and fungi to grow. Moisture also helps these micro-organisms survive and multiply.
Experiment:
Aim: To observe the decomposition process undertaken in a compost bin, and monitor the rate of breakdown.
Time: 30 minute set up with weekly observations over 3-4 weeks
What each student will need:
- Clear 2ltr plastic bottle with lid
- Two cups of fruit and vegetable scraps
- Two cups of dried grass clippings/leaves
- Two cups of garden soil
- One cup of shredded newspaper
- Spray bottle containing water
- One tablespoon of fertilizer (eg blood and bone)
- Clear tape
- Scissors
- Permanent marker
- Gloves
Method:
- Cut around the bottle neck to form a flip top lid (large enough to pour the ingredients in).
- Pour 2-3 cm of soil into the bottom of the bottle.
- Using the spray bottle, moisten the soil.
- Add 2-3 cm of fruit and vegetable scraps on top of the soil.
- Add another 1 cm layer of soil.
- Using gloves, sprinkle with 1/3 of the fertiliser over the soil.
- Add a layer of leaves and grass.
- Cover with another 1 cm layer of soil.
- Lay moist newspaper over the soil.
- Repeat steps 4-9.
- Tape the top of the bottle closed.
- Mark the top of the compost on the side of the bottle.
- Place bottles in a sunny spot.
- Once a week, mark the height of the compost on the bottle and observe the changes in volume and rate of decomposition.
TIP: if the compost gets too moist, take the lid off to dry it out. Alternately, if the compost gets too dry, spray it with a little water.
Results:
Discuss the process of decomposition. Research and draw a picture of the decomposition cycle. What happened to the food scraps? What happened to the paper? Did the overall volume of the compost increase or decrease over the period of observation? Did you see any mould or fungi growing in the compost? Research what should not be put in the compost bin and why. Once you have finished the experiment, don’t forget to put the compost on the garden!
Further activities:
Start a compost bin at home or school. Design a poster outlining what should and should not be put in the compost bin. Conduct an experiment to assess growth rates of seedlings using compost and poor quality soil.
DID YOU KNOW?
Ever stopped to think where oxygen comes from? Your first thought may be a rainforest, but marine organisms take the bait. Plankton, seaweed and other photosynthesizers produce over half of the world’s oxygen. We know the answer to this and other fun science facts, but here are other ocean mysteries that scientists can’t explain.
Lost land animals may not be able to find their way home, but sea animals might. According to the U.S. Geological Survey (USGS), “there is evidence that some animals, like sea turtles and salmon, have the ability to sense the Earth’s magnetic field and to use this sense for navigation.”
NASA experts believe there could be anywhere from 100 billion to 400 billion stars in the Milky Way galaxy, Snopes reports. However, a 2015 paper published in the journal Nature estimated that the number of trees around the world is much higher: 3.04 trillion.