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Nuclear reactions in the core of a star convert ___ to helium.

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Hydrogen is converted to helium in the core of a star through nuclear fusion.

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Any massive system of hundreds of billions of stars held together by gravity.

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A galaxy is a massive system of stars, gas, dust, and dark matter held together by gravity.

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Write 564,000,000 in scientific notation.

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5.64 x 10^8 is the scientific notation for 564,000,000.

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A process of inquiry that results in the accumulation of knowledge.

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The scientific method is a systematic process used to investigate phenomena, acquire new knowledge, or correct and integrate previous knowledge.

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A fair test designed to give a reliable and unbiased answer to the question being investigated.

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An experiment is a controlled procedure carried out to discover, test, or demonstrate a fact or general truth.

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The smallest unit of an element that retains the properties of that element.

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An atom is the basic unit of a chemical element.

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A substance made of two or more different types of atoms bonded together.

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A compound is a chemical substance formed from two or more elements in a fixed ratio.

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The force of attraction between two objects due to their mass.

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Gravity is the force that attracts two bodies towards each other.

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The change in position of an object over time.

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Motion is the process of changing position.

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The amount of matter in an object, typically measured in grams or kilograms.

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Mass is a measure of the amount of matter in an object.