7th Grade Final Review

According to the law of conservation of matter, which statement about chemical reactions is true?

• Every atom destroyed in a chemical reaction must be replaced.

• Energy is created as atoms are destroyed in chemical reactions.

• Atoms are created by some reactions and destroyed by others.

• Atoms cannot be created or destroyed by chemical reactions.

Select ALL the correct answers.

Two substances are combined. Which observations would likely indicate that a chemical reaction is occurring and new substances are being formed?

• production of a gas

• change in color

• production of light

• change in mass

Scientists have recently discovered a species of sea slug that "steals" the genes for photosynthesis from the algae that it eats. What can the sea slug now do that most animals cannot?

• reproduce

• live forever

• turn into a plant

• make their own food

During photosynthesis, plants absorb energy from sunlight, they take in water from the soil using their roots, and they take in carbon dioxide from the atmosphere. What is produced in the leaves of plants, in addition to oxygen?

• sugar

• hydrogen

• minerals

• all of these

Cellular respiration describes the process that living cells use to release energy by combining sugar and oxygen. The primary chemical changes that happen during cellular respiration are shown in the equation below.The mass of the reactants is <br> _______________ as the mass of the products.

• less than

• greater than

• the same

• half of

A scientist would like to demonstrate that cells are the basic structural and functional unit of living organisms. Which of the following experiments should she perform?

• add several seeds to pots with soil and monitor the growth of the plants

• observe samples of plant tissue under a microscope at a high magnification

• place individual cells in a Petri dish with food and monitor their ability to grow

• observe whether organisms appear in a sealed container of broth after it is boiled

Katia uses a microscope to study cells from different organisms. She notices two different structures within the cells. What kinds of cells contain these structures?

• Structure 1 is in both kinds of cells, and structure 2 is only in animal cells.

• Structure 1 is only in plant cells, and structure 2 is in both kinds of cells.

• Structure 1 is only in animal cells, and structure 2 is only in plant cells.

• Both structure 1 and structure 2 are in both kinds of cells.

Potato cells usually do not contain chloroplasts. If you examined a potato cell under a microscope, how could you tell that it was a plant cell?

• cell wall

• cell membrane

• nucleus

• cytoplasm

Why do some objects have less kinetic energy over time?

• Some gets lost

• The energy is changed

• They slow down

• There is too much friction

A supernova is a large explosion that takes place at the end of a star's life cycle. Although supernovas only burn for a short amount of time, they can tell scientists a lot about the universe. Scientists use electromagnetic waves to detect supernovas. Why are electromagnetic waves used instead of sound waves?

• Electromagnetic waves are created by physical vibrations.

• Electromagnetic waves can travel in vacuums

• Electromagnetic waves cannot be absorbed.

• Electromagnetic waves travel slower than sound waves.