14. a student is trying to find out which type of fertilizer is best for getting a plant to grow as tall as possible. she keeps all the plants indoors on the same classroom window sill. what is the controlled variable (cv) in this experiment?
a. the type of fertilizer
b. the place where the plants are kept (same indoor window sill)
c. the brand of fertilizer
d. the student measuring the plants
15. a scientific theory is __________.
a. a random guess that has not been tested
b. a well - tested explanation based on many observations and experiments
c. a rule that describes a pattern in nature but does not explain it
d. an opinion that scientists agree on
16. what is anything that has mass and takes up space?
a. science
b. matter
c. substance
d. atoms
17. is it a physical change or a chemical change when a reaction occurs, and the product is different from the starting material?
a. physical change b. chemical change
18. is melting butter for popcorn a chemical or physical change?
a. physical change b. chemical change
19. is dissolving sugar in water
a. physical change b. chemical change
20. is letting a nail rust
a. physical change b. chemical change
21. a marshmallow is toasted over a campfire.
a. physical change b. chemical change
22. an apple is cut.
a. physical change b. chemical change
23. what is the definition of conduction?
a. when heat is transferred from objects like rays of light or electromagnetically.
b. a hot liquid or air that expands, becomes less dense, and rises or becomes more dense, and sinks.
c. when heat transfers from objects that are touching.
d. when heat transfers through the heater or ac in your house.

Question

14. a student is trying to find out which type of fertilizer is best for getting a plant to grow as tall as possible. she keeps all the plants indoors on the same classroom window sill. what is the controlled variable (cv) in this experiment?
a. the type of fertilizer
b. the place where the plants are kept (same indoor window sill)
c. the brand of fertilizer
d. the student measuring the plants
15. a scientific theory is __________.
a. a random guess that has not been tested
b. a well - tested explanation based on many observations and experiments
c. a rule that describes a pattern in nature but does not explain it
d. an opinion that scientists agree on
16. what is anything that has mass and takes up space?
a. science
b. matter
c. substance
d. atoms
17. is it a physical change or a chemical change when a reaction occurs, and the product is different from the starting material?
a. physical change  b. chemical change
18. is melting butter for popcorn a chemical or physical change?
a. physical change  b. chemical change
19. is dissolving sugar in water
a. physical change  b. chemical change
20. is letting a nail rust
a. physical change  b. chemical change
21. a marshmallow is toasted over a campfire.
a. physical change  b. chemical change
22. an apple is cut.
a. physical change  b. chemical change
23. what is the definition of conduction?
a. when heat is transferred from objects like rays of light or electromagnetically.
b. a hot liquid or air that expands, becomes less dense, and rises or becomes more dense, and sinks.
c. when heat transfers from objects that are touching.
d. when heat transfers through the heater or ac in your house.

Accepted Answer

### Question 14
# Brief Explanations:
A controlled variable is kept constant. Here, the place (same window sill) is kept constant. A is the independent variable, C is part of the independent variable, D is not a variable being controlled for the experiment's conditions.
# Answer:
B. The place where the plants are kept (same indoor window sill)

### Question 15
# Brief Explanations:
A scientific theory is a well - tested explanation from many observations/experiments. A is a hypothesis, C is a law, D is not a theory (theories are based on evidence, not just agreement).
# Answer:
B. A well - tested explanation based on many observations and experiments

### Question 16
# Brief Explanations:
Matter is defined as anything with mass and volume (takes up space). Science is a study, substance is a type of matter, atoms are building blocks of matter.
# Answer:
B. Matter

### Question 17
# Brief Explanations:
A chemical change produces a new substance. If the product is different, it's a chemical change (physical change doesn't produce new substances).
# Answer:
B. Chemical change

### Question 18
# Brief Explanations:
Melting butter changes its state (solid to liquid) without new substance. Physical change (no chemical reaction, just state change).
# Answer:
A. Physical change

### Question 19
# Brief Explanations:
Dissolving sugar in water is a physical change (sugar can be recovered, no new substance, just a mixture).
# Answer:
A. Physical change

### Question 20
# Brief Explanations:
Rusting a nail involves iron reacting with oxygen to form rust (new substance), so it's a chemical change.
# Answer:
B. Chemical change

### Question 21
# Brief Explanations:
Toasting a marshmallow causes chemical reactions (browning, new compounds), so it's a chemical change.
# Answer:
B. Chemical change

### Question 22
# Brief Explanations:
Cutting an apple only changes its shape, no new substance. So it's a physical change.
# Answer:
A. Physical change

### Question 23
# Brief Explanations:
Conduction is heat transfer between touching objects. A is radiation, B is convection, D is not a definition of conduction.
# Answer:
C. When heat transfers from objects that are touching.

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Question 14

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Question 15