Answer:
9000 BC
Explanation:
Although various copper tools and decorative items dating back as early as 9000 BCE have been discovered, archaeological evidence suggests that it was the early Mesopotamians who, around 5000 to 6000 years ago, were the first to fully harness the ability to extract and work with copper.
They're based on hydrogen.
Answer:
This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity. greenhouse effect The warming of Earth's atmosphere due to the buildup of heat-trapping gases, such as carbon dioxide and methane.
Explanation:
Answer:
c. contraction
Explanation:
Heating will cause substances to expand, or change their state (like solid to liquid) or it may be a chemical reaction.
