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Science Working Models for Class 7

Science models for class 7 students can be any genius experiments or working models that students can display in their science fair or science exhibitions. As the title suggests, this is a scaled representation of an existing invention. You are asked to make a WORKING model that simulates the operation of, and the scientific principles behind, an existing technology. You should choose a model which clearly illustrates a scientific principle. When you think about it, it is easy to understand the importance of models in science.

Many times the objects of a scientist’s attention are too small to be observed directly, or they may be inaccessible for direct visual study, as would be the case for the center of the Earth or the surface of a distant galactic object. These models are intended to educate people about the concept being illustrated. For example, if you wanted to show how electrons flow through a wire you couldn’t use electrons(because they are so small) but would use something large enough to see to represent the electrons.

How to Grow Lettuce at Home

Lettuce How to Grow Lettuce at Home

Lettuce grows best during cool weather. Head types are particularly sensitive to warm weather and rarely grow well when the temperature gets higher than 75°F. Some types of lettuce grow satisfactorily at lower, warmer elevations in Hawaii, but even for those varieties, growth is generally better during cooler seasons. When the temperature is too high for the variety, lettuce plants will have symptoms including leaf tip-burn, early bolting (flowering), and bitterness, and head types will also have loose heads. The term “greens” is often used to refer to a number of leafy vegetables which belong to several unrelated plant families. Common greens that could be produced in a greenhouse include spinach, turnip greens, collards and mustard greens. Specialty greens, such as arugula, sorrel, chicory, and Asian greens, also show potential.

When to Plant

  • Minimum soil temperature should be 50°.
  • Leafy greens grow best at 55°‐60°; colder weather will merely slow growth.
  • Plant early spring through early summer; late summer for fall harvest.
  • Hot weather causes greens to bolt or set seed which can cause leaves to become coarse and bitter. Look for slow‐bolt or long‐standing varieties.

How to Plant

  • Direct sow: remove all weeds, amend the soil if needed, level bed, sprinkle lightly with seed,
    cover seeds with ¼” soil; thin plants to avoid overcrowding.
  • Transplants: choose vigorous plants, soak well in pots to ensure thoroughly watered, loosen
    roots, plant in ground or container.

How to Harvest

  • Snip entire plant at ground level.
  • Pinch off lower leaves allowing the plant to continue to produce more leaves.
  • Best to harvest in the early morning before leaves begin to wilt.

Cultural Considerations

  • Greens are adaptable to various soil types.
  • Can be heavy feeders; apply ammonium sulfate at planting time and again in 3‐4 weeks.
  • Vegetables require approximately 1” of water per week; water greens frequently.

Egg In A Bottle

Egg-Experiment Egg In A Bottle

Eggs are generally something that you consume as a source of food but with the help of this project, you will learn something new about science. This experiment will show that the use of oxygen molecules in a particular area causes a loss of air pressure.

Materials

  • Medium sized boiled egg.
  • Boil eggs by placing eggs in a pot with enough to cover completely by 1-2 inches above eggs. Bring them close to a boil. Once the water is boiling, turn the heat to medium and allow to cook for 10-minutes.
  • Remove from heat and place under cool water to chill them quickly.
  • Crack and peel.
  • Bottle with a neck just small enough that the egg won’t fall in (Erlenmeyer Flask, 1000 ml is perfect, see below). You may want to put a little water around the rim to guard against tearing of the egg.

Procedure

There are a number of ways to get the egg into the bottle:

  • If you are going to use paper, wad it up, drop it in the bottle, and light it and allow it to burn out and immediately (be sure the egg shell is removed and the egg is moist). Put the egg in the neck of the bottle. The egg will be sucked into the bottle. This happens because as the air inside the bottle cools and takes up less space. Now, the external pressure outside the bottle will force the egg into the bottle in order to balance the pressure. To get the egg out of the bottle, turn the bottle upside down with the egg resting on the inside of the mouth of the bottle. Place your mouth over the mouth of the bottle and blowhard. When you stop blowing, the egg will pop out.
  • Another way to do this is to use hot water. If you take the flask and hold it under hot water from the tap for 30-40 seconds and then place the egg on top (the neck) and then turn the water to cold, it will suck in the egg inside. Conversely, you can remove the egg by tilting the bottle and then allowing hot water to run on the flask bottom.

Conclusion

An air pressure difference causes movement of particles. The amount of pressure is determined by the difference of pressure in the air and the amount of area affected.

Benefits of these models

These models would help the students learn about the subjects they study more deeply. These models will serve as a practical learning of sorts. Students would also appreciate the subjects they learn more deeply.

Check out our article on Science working models for class 8 here.

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