Answer:
Las moléculas de agua son muy cohesivas debido a la polaridad de la molécula. Es por eso que puede llenar un vaso de agua apenas por encima del borde sin que se derrame. Todas las sustancias, incluido el agua, se vuelven menos densas cuando se calientan y más densas cuando se enfrían.
Explanation:
Answer:
space
Explanation:
As air gets warm, the air molecules have more energy and move around more, taking up more space. As the warm air expands, it becomes less dense than the cold air, so rises up and floats above the cold air.
Answer:
Coal: 7.4 billion tonnes
Explanation:
The World Coal Association estimates that there are more than one trillion tonnes of coal reserves worldwide, enough to last 150 years at current rates of production, so it is unsurprising to see coal ranked as the most-mined mineral in the world.
While China has consistently led the world in production – the country was responsible for 3.3 billion tonnes in 2016 – this was down 16% from the 3.9 billion tonnes produced in 2012. Chinese coal output slumped below the 3.4 billion tonne-threshold predicted in 2016 and the trend may continue, as renewable energy sources become more widespread.
The Chinese decline has mirrored a trend in worldwide coal production, which fell to 7.4 billion tonnes in 2016 from 8.2 billion in 2012. While coal production has increased in Australia and Russia in the last five years, both South Africa and the US have seen sharp declines in production of anthracite and bituminous coal. American coal production in particular has fallen from over 900 million tonnes in 2012 to 782 million in 2016, the lowest figure since 1979.
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