8th grade science test: unit 1: introduction to 8th grade science
instructions: read each question carefully. answer in complete sentences where appropriate. write your responses directly below each question.
1. a student observes that an ice cube melts faster on a metal surface than on a wooden one. using the steps of the scientific method, explain how the student could design an experiment to test how surface type affects melting speed. what steps should they follow?
2. a student wanted to test if adding salt to water makes it boil faster. they used two pots with the same amount of water on identical burners: pot a (no salt): boiled in 9 minutes pot b (2 tablespoons of salt): boiled in 7 minutes they repeated the test three times and got similar results. write a cer (claim, evidence, reasoning) based on this investigation.
3. in an experiment where different amounts of fertilizer are added to tomato plants to measure tomato production:
- identify the independent variable
- identify the dependent variable
- list at least two constants
- explain what the control group would be and why its important
4. in your own words, explain the difference between a scientific hypothesis, scientific theory, and scientific law and provide one example of each.
5. you notice that a puddle outside your school is gone by the afternoon.
- write one observation
- write one inference
- explain the difference between an observation and an inference

Question

8th grade science test: unit 1: introduction to 8th grade science
instructions: read each question carefully. answer in complete sentences where appropriate. write your responses directly below each question.
1. a student observes that an ice cube melts faster on a metal surface than on a wooden one. using the steps of the scientific method, explain how the student could design an experiment to test how surface type affects melting speed. what steps should they follow?
2. a student wanted to test if adding salt to water makes it boil faster. they used two pots with the same amount of water on identical burners: pot a (no salt): boiled in 9 minutes pot b (2 tablespoons of salt): boiled in 7 minutes they repeated the test three times and got similar results. write a cer (claim, evidence, reasoning) based on this investigation.
3. in an experiment where different amounts of fertilizer are added to tomato plants to measure tomato production:
  - identify the independent variable
  - identify the dependent variable
  - list at least two constants
  - explain what the control group would be and why its important
4. in your own words, explain the difference between a scientific hypothesis, scientific theory, and scientific law and provide one example of each.
5. you notice that a puddle outside your school is gone by the afternoon.
  - write one observation
  - write one inference
  - explain the difference between an observation and an inference

Accepted Answer

# 1.
## Explanation:
### Step1: State the problem
The problem is to test how surface type affects the melting speed of an ice - cube.
### Step2: Formulate a hypothesis
A possible hypothesis could be: Ice cubes melt faster on metal surfaces than on wooden surfaces because metals are better conductors of heat.
### Step3: Design the experiment
- Gather materials: identical ice - cubes, a metal surface, a wooden surface, a stopwatch.
- Place one ice - cube on the metal surface and one on the wooden surface simultaneously.
- Start the stopwatch as soon as the ice - cubes are placed.
- Record the time it takes for each ice - cube to completely melt.
### Step4: Conduct the experiment
Repeat the above steps multiple times to ensure accuracy.
### Step5: Analyze the data
Compare the average melting times for the metal and wooden surfaces.
### Step6: Draw conclusions
If the ice - cube on the metal surface has a shorter average melting time, the hypothesis is supported.

# 2.
## Claim:
Adding salt to water makes it boil faster.
## Evidence:
When two pots with the same amount of water on identical burners were used, pot A (no salt) boiled in 9 minutes and pot B (2 tablespoons of salt) boiled in 7 minutes. The test was repeated three times with similar results.
## Reasoning:
Salt is a solute. When dissolved in water, it increases the boiling point elevation. But in this case, with the same heat source and starting conditions, the presence of salt somehow reduces the time to reach the boiling point. This could be due to salt's effect on the water's heat - transfer properties or its ability to disrupt water's hydrogen - bonding network, allowing the water to reach the boiling point more quickly.

# 3.
## Independent variable:
The amount of fertilizer added to the tomato plants.
## Dependent variable:
Tomato production (e.g., number of tomatoes, weight of tomatoes).
## Constants:
- The type of tomato plants (to ensure genetic similarity).
- The amount of sunlight the plants receive (as it affects growth).
## Control group:
The group of tomato plants that receive no fertilizer. It is important because it provides a baseline for comparison. By comparing the tomato production of the fertilized plants to the non - fertilized ones, we can determine the actual effect of the fertilizer on tomato production.

# 4.
## Scientific hypothesis:
A scientific hypothesis is a proposed explanation for a phenomenon, based on limited evidence as a starting point for further investigation. It is testable. Example: If plants are exposed to more sunlight, then they will grow taller.
## Scientific theory:
A scientific theory is a well - substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experimentation. Example: The theory of evolution by natural selection explains how species change over time.
## Scientific law:
A scientific law is a statement that describes an observed phenomenon. It is a generalization that is based on repeated experimental observations. Example: Newton's law of universal gravitation, which states that every particle attracts every other particle in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

# 5.
## Observation:
The puddle outside the school is gone by the afternoon.
## Inference:
The puddle evaporated due to the heat from the sun during the day.
## Difference:
An observation is a direct, factual record of something that is perceived through the senses. An inference is a conclusion drawn from observations and prior knowledge. The observation is simply stating what was seen, while the inference is an interpretation of why it happened.

QUESTION IMAGE

Question

Explanation:

1.

Step1: State the problem

Step2: Formulate a hypothesis

Step3: Design the experiment

Step4: Conduct the experiment

Step5: Analyze the data

Step6: Draw conclusions

2.

Claim:

Evidence:

Reasoning:

3.

Independent variable:

Dependent variable:

Constants:

Control group:

4.

Scientific hypothesis:

Scientific theory:

Scientific law:

5.

Observation:

Inference:

Difference:

Answer: