For each item below, specify the independent and dependent variables, as well as constants. A study was done to find if different tire treads affect the braking distance of a car. The time it takes to run a mile depends on the person’s running speed. The height of bean plants depends on the amount of water they receive. The higher the temperature of the oven, the faster a cake will bake. Lemon trees receiving the most water produced the most lemons. An investigation found that more bushels of potatoes were produced when the soil was fertilized more. Students measured the temperature of the water at different depths in Lake Skywalker and found that the temperature varied. The amount of pollution produced by cars was measured for cars using gasoline containing different amounts of lead. The transfer of heat by air currents (or currents in a liquid) is called ______________________________. What often occurs at tectonic plate boundaries? What is the estimated temperature of the Earth’s inner core in Celsius? How did the Himalayan Mountains form? What are electrically charged atoms called? How is air heated near the Earth’s surface?
The Correct Answer and Explanation is:
Tire Treads and Braking Distance:
- Independent Variable: The type of tire tread.
- Dependent Variable: The braking distance of the car.
- Constants: The type of car, road conditions, car speed, weather, and other environmental factors that could affect braking.
Explanation: The study investigates how different tire treads affect braking distance. The tire treads are the variable being changed to see its effect on braking distance, which is the outcome being measured. Constants ensure that the test is fair and that only the tire treads are being tested.
2. Running Time and Speed:
- Independent Variable: The person’s running speed.
- Dependent Variable: The time it takes to run a mile.
- Constants: The distance of the mile, the surface of the track, the health of the runner, and other environmental factors like weather.
Explanation: The running speed is the factor being manipulated to see how it influences the time taken to run a mile. The constants (such as the mile distance) ensure that the comparison is based solely on running speed.
3. Bean Plant Growth and Water:
- Independent Variable: The amount of water the plants receive.
- Dependent Variable: The height of the bean plants.
- Constants: Type of plant, soil type, light, and temperature conditions.
Explanation: The amount of water is being varied to study its effect on the height of the bean plants. The constants, such as the type of plant and soil, ensure that the height change is due to water and not other factors.
4. Temperature of Oven and Cake Baking:
- Independent Variable: The temperature of the oven.
- Dependent Variable: The time it takes for the cake to bake.
- Constants: The type of cake, the ingredients, the oven, and the size of the cake.
Explanation: By changing the oven temperature, the study examines how it affects the baking time of the cake. The other factors (like cake size or ingredients) remain constant to ensure fair testing.
5. Lemon Trees and Water:
- Independent Variable: The amount of water the lemon trees receive.
- Dependent Variable: The number of lemons produced by the trees.
- Constants: The type of lemon tree, soil type, temperature, and sunlight.
Explanation: The study focuses on the effect of water on lemon production. The amount of water varies, and the number of lemons produced is the result being measured.
6. Potato Production and Fertilizer:
- Independent Variable: The amount of fertilizer applied to the soil.
- Dependent Variable: The number of bushels of potatoes produced.
- Constants: The type of potatoes, the soil, the amount of water, and environmental factors like weather.
Explanation: The experiment tests how different levels of fertilizer affect potato production. The constants ensure that the fertilizer is the main influencing factor.
7. Water Temperature and Depth in Lake:
- Independent Variable: The depth of the water in Lake Skywalker.
- Dependent Variable: The temperature of the water.
- Constants: The location in the lake, weather conditions, time of year, and other factors that might influence the temperature.
Explanation: This investigation measures how temperature changes with depth in a lake. Depth is the factor being manipulated to see its effect on water temperature, which is the observed outcome.
8. Pollution and Lead in Gasoline:
- Independent Variable: The amount of lead in the gasoline.
- Dependent Variable: The amount of pollution produced by cars.
- Constants: The type of car, road conditions, weather, and other variables that might influence pollution.
Explanation: The study tests the effect of different lead levels in gasoline on pollution levels. The variables such as car type and road conditions remain constant to isolate the effect of lead on pollution.
9. Transfer of Heat by Air Currents:
- Answer: The transfer of heat by air currents (or currents in a liquid) is called convection.
Explanation: Convection is the process through which heat is transferred in fluids (air or liquid) by the movement of warmer and cooler regions. As the warmer fluid rises and cooler fluid sinks, heat is transferred, creating currents.
10. Tectonic Plate Boundaries:
- Answer: At tectonic plate boundaries, earthquakes, volcanic activity, and mountain formation often occur.
Explanation: Tectonic plate boundaries are regions where plates meet, and their interactions can cause significant geological phenomena like earthquakes and the formation of volcanoes and mountains, depending on the type of boundary (convergent, divergent, or transform).
11. Temperature of Earth’s Inner Core:
- Answer: The estimated temperature of the Earth’s inner core is approximately 5,200°C.
Explanation: The Earth’s inner core is extremely hot, primarily due to residual heat from the planet’s formation and the ongoing decay of radioactive elements. The temperature is enough to melt iron, which makes up the core.
12. Formation of the Himalayan Mountains:
- Answer: The Himalayan Mountains formed from the collision of the Indian Plate with the Eurasian Plate.
Explanation: The Himalayas were created millions of years ago when the Indian Plate collided with the Eurasian Plate. This collision caused the land to buckle and fold, resulting in the formation of these massive mountains.
13. Electrically Charged Atoms:
- Answer: Electrically charged atoms are called ions.
Explanation: Ions are atoms that have gained or lost electrons, resulting in a net electrical charge. If an atom loses electrons, it becomes a positively charged ion (cation), and if it gains electrons, it becomes a negatively charged ion (anion).
14. How Air Is Heated Near Earth’s Surface:
- Answer: Air near the Earth’s surface is heated primarily through conduction and convection.
Explanation: The Earth’s surface absorbs solar radiation and warms up, which in turn heats the air directly above it. Heat is transferred to the air through conduction, and then convection currents spread the heat through the atmosphere, warming the air.
