Layers that are less dense, such as the crust<span>, float on layers</span> that are denser, such as the mantle. Both oceanic crust and continental crust are less thick than the mantle, but the marine crust is denser than continental crust. This is partly why the continents are at a higher elevation than the ocean floor.
Explanation:
- Microscopes: Anton van Leeuwenhoek is considered the precursor of cellular and experimental biology as well as microbiology, in 1674, he used a homemade microscope to become the first person to discover microbes, he described seeing animalcules in a drop of water, he also discovered red blood cells and bacteria in 1676.
- Pasteurization: it's a process in which water and certain foods like milk and juice, are treated with mild heat, usually before boiling point, to eliminate pathogens. It was named after Louis Paster, who in the 1860s demonstrated that heating beverages to about 57°C for a few minutes could prevent abnormal fermentation, this treatment also destroys microorganisms that cause spoilage and so it prolongs the storage time of food.
- Koch postulate: In 1890, Robert Koch set out his criteria for judging whether a bacteria is the cause of a disease. These postulates are: The bacteria must be present in every case of the disease, it must be isolated from the host and grow in culture, the disease is reproduced when a bacteria from the pure culture is inoculated into a healthy host, the bacteria must be recoverable from the infected host. These postulates are useful to find the cause-effect relationship between bacteria and clinical disease.
- Antibiotics: In 1928, Alexander Fleming, discovered mold as an antibacterial agent after this one contaminated his<em> Staphylococcus aureus </em>dishes, inhibiting it's growing, this mold was then named penicillin and it was the beginning of a transformation in human health.
- Vaccines: the first successful vaccine development was introduced in 1796 by Edward Jenner, this advance was achieved after he followed up his observation of milkmaid who previously caught cowpox did not later catch smallpox by showing that inoculated cowpox protected against inoculated smallpox.
I hope you find this information useful and interesting! Good luck!
Answer:
3758 kJ
Explanation:
Given:
Mass of the ice = 10 kg = 10 × 1000 = 10,000 g
Initial temperature of the ice = -20° C
Now,
The ice will start to melt when it will reach a temperature of 0° C
and, specific heat of ice, C = 2090 J/kg
Therefore,
Heat required to heat the ice from -20° C to 0° C
Q₁ = mCΔT
or
Q₁ = 10 × 2090 × (0 - (-20 ))
or
Q₁ = 418000 J
also,
Heat of fusion required to change the ice into liquid without any change in temperature.
For ice the heat of fusion = 334 J/g
Hence,
Energy needed by ice to melt, Q₂ = 334 × 10,000 J = 3,340,000 J
Hence, the total heat required = Q₁ + Q₂
= 418000 J + 3,340,000 J
= 3758000 J
= 3758 kJ
It ends in the gulf of mexico.
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