Leap 2025 Science

The law of conversation of energy states that energy can be neither created or destroyed, but it can change its_______

• obsrvation

• fome

• big papa

• form

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What does DC stand for?

What does AC stand for?

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They typically are rockets that are guided and contain explosives of some kind.

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Rely on the explosive power of the fuel within the engine to produce work.

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In science class, Marvin studies the effects of mixing substances together. Marvin and his partner measure and collect 450 mL of warm water and 50 mL of salt in a large, glass beaker. They measure the mass of each substance and record the results in the table below.Part A: Marvin and his partner measured the mass of a large, glass beaker. They mix the two substances together in the beaker. They observed a slight color change in the water and that much of the salt disappeared after mixing the two substances. Then, they measured the mixture and subtracted the mass of the beaker so they could record the mass of the substances after they mixed them together.Which estimate is the mass of the mixture?

• 450 grams

• 909.2 grams

• 454.6 grams

• 445.4 grams

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In science class, Marvin studies the effects of mixing substances together. Marvin and his partner measure and collect 450 mL of warm water and 50 mL of salt in a large, glass beaker. They measure the mass of each substance and record the results in the table below.
Part B: Which statement best explains Part A?

• The water was warm and made some of the salt dissolve. When salt dissolves, it loses its mass.

• Marvin and his partner mixed the water and the salt. This made the mass of both substances double.

• The water was warm and made some of the salt dissolve. Both substances lost a little mass because they were mixed together.

• Marvin and his partner combined the water and the salt. The total mass of each substance did not change even though they were mixed together.

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Lamar is studying water quality in his science class. He learns that salt water is seeping into his neighboring town’s water supply and makes the water dangerous to drink. Lamar’s teacher challenges his class to investigate ways to identify salt water without tasting it. Part A: Lamar has one glass of pure water and one glass of salt and water. The two liquids look exactly alike. What investigation can Lamar perform, without tasting the water, to find out which glass contains the salt water?

• Lamar couldn’t do it. A chemical change has taken place.

• Lamar could evaporate the water to see which cup leaves salt behind.

• Lamar couldn’t do it. It is not possible to identify clear liquids without tasting them.

• Lamar could shine a light into the water and check for salt conductivity.

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Lamar is studying water quality in his science class. He learns that salt water is seeping into his neighboring town’s water supply and makes the water dangerous to drink. Lamar’s teacher challenges his class to investigate ways to identify salt water without tasting it. Part B: What measurements can Lamar take before he conducts his investigation in Part A to provide evidence of which cup contained the salt water?

• Find the volume of both liquids to see which one took up the most space.

• Measure the temperature of each liquid to provide evidence that a chemical change had taken place.

• Measure the mass of each cup to see which one had the most matter.

• Use a photometer to observe which cup had the most salt conductivity.

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Hoey develops an experiment to investigate how different substances react when they are mixed with water. Before mixing the materials together, she measured the mass and temperature of the substances. During the experiment, Dr. Hoey mixes calcium and water in a glass with a plastic rod. Then, she mixes baking soda and water in a glass with a plastic rod. The results of the experiment are below. Which of the following claims can Dr. Hoey make based on her investigation?

• Solution A is a new substance because after the calcium and water mixed, the temperature increased and the color changed.

• Solution B is a new substance because after the baking soda and water mixed, the solution was cloudy and the temperature remained the same.

• Solution B is a new substance because after the baking soda and water mixed, the mass of the solution is equal to the mass of the baking soda and water before they were mixed.

• Solution A and B are new substances because each solution stayed the same when they were mixed together.

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